WILLIAM  R.  PERKINS 
LIBRARY 


DUKE  UNIVERSITY 


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in  2016  with  funding  from 
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A TEXT-BOOK 

II 

OP 

NAVAL  ORDNANCE  AND  GUNNERY. 

PREPARED  POR  THE 

USE  OF  THE  CADET  AIIDSHIPMEN 

f AT  THE 


LKited  States  Xaa^al  Academy. 


M V BY 

V>0 

A.  f:  gooke, 

COiniANDER,  U.S.X., 


IN  CHARGE  OF  INSTHUCTION  IN  ORDNANCE  AND  GUNNERY 
AT  THE  U.  S.  NAVAL  ACADEMY. 


Aew-York  : 

JOHN  WILEY  & SON,  15  ASTOR  PLACE. 
1875. 


Entered,  according  to  Act  of  Congress,  in  the  }'ear  1875,  by 
A.  P.  COOKE, 

In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


31 

FEh  141945 

^ Serial  hecord  Division 
Ths  Llbrarir  of  CongroM 
Copy 


Tt.t.itkthattonS  ENSR.A.VBD  ON  WOOD  BY  CH.YKLES  AIcRRAY,  XEW  YOltK. 


John  F.  Trow  & Son,  Printers, 
205-213  East  i2th  St.,  New  York. 


C77Z 


PREFACE. 


Tins  work  was  undertaken  hy  tlie  Instructors  in  the 
Department  of  Ordnance  and  Gunnery  at  the  Naval 
Academy,  to  supply  a deficiency  which  has  long  heen 
felt,  and  to  I'ender  available,  as  far  as  possible,  in  a sin- 
gle volume  the  course  of  instruction  hitherto  pursued 
l;)y  the  Cadet  JMidshipmen;  thus  relieving  them  from  the 
necessity  which  at  present  exists,  of  copying  manuscript 
notes  on  the  subject. 

The  unsettled  condition  of  various  rpiestions  relating 
to  ordnance,  makes  it  necessary  to  prepare  suitable  text- 
books for  to-day,  which  should  be  I'evised  as  often  as 
the  progressive  development  of  the  suliject  seems  to  re- 
quire, Explosive-agents,  rilled  ordnance,  gun-carriages, 
and  many  other  branches  of  the  subject,  are  in  a state 
of  transition,  and  it  is  impos.sible  at  the  present  mo- 
ment to  produce  a com])lete  and  entirely  satisfactory 
treatise  on  these  subjects. 

It  is  thought  that  no  intelligent  progress  can  be 
made  in  the  subject  of  the  manufacture  of  cannon,  and 
of  many  of  the  stores  used  in  their  service,  without  some 
preliminary  knowledge  of  the  metallurgy  of  iron,  and  of 
the  means  of  producing  the  metals  employed.  As  this 
sul)ject  is  not  taught  in  an}'  other  department  of  the 
Academy  it  is  given  a place  here. 


IV 


PREFACE. 


A sufficient  knowledge  of  niatheinatics,  physics  and 
chemistry,  is  attained  hythe  students  in  tlieir  previous 
course,  to  enaT>le  them  to  grasp  all  the  subjects  treated 
in  this  work. 

The  sul)ject  of  Field  Fortifications  ’was  formerly 
taught  in  this  department,  l)ut  for  want  of  time  and  an 
appropriate  text-l)ook  it  was  taken  out  of  the  course. 
The  last  chapter,  entitled  “Naval  Operations  on  Shore,” 
has  Ijeen  arranged  with  a view  of  covering  briefly  the 
necessary  ground  in  this  l)ranch. 

In  the  compilation  of  the  material  employed,  the 
writer  is  greatly  indebted  to  Lieut.-Commanders  C.  Ab 
Tracy,  G.  W.  Coffin,  N.  Ludlow,  and  C.  F.  Goodrich,  to 
Lieut.  J.  C.  Soley,  and  to  Professors  J.  M.  Eice  and  D. 
Fisher.  The  advice,  assistance,  and  manuscript  notes 
of  many  other  officers  have  likewise  aided  materially 
in  the  pre2:>aration  of  this  work. 


Department  of  Ordnance  and  Gunnery, 
U.  S.  Naval  Academy,  Annapolis, 
March,  1875. 


CONTENTS. 


CHAPTER  I. 

CANNON  METALS. 

Section  1. — Metallurf/y  of  Iron. 

Preparation  of  Iron  Ores — Smelting;— Fluxes — Fuel — The  Blast-furnace — 
Charging — Temperature  of  Blast — Hot-hlast — Method  of  Heating  the  Blast — 
Blowing  in — Working  of  the  Furnace — Chemical  Action  in  the  Furnace-^Pro- 
duction  of  Gun-iron. 


Section  II. — Cast-iron. 

Composition  of  Cast-iron — Varieties  of  Cast-iron  — Gray  Cast-iron — 
White  Cast-iron — -Mottled  Cast-iron — Classification  of  Pig-iron — Variations 
in  Composition  of  Cast-iron. 

Section  III. — WrougM-iron. 

Peculiarities — How  produced — Conversion  of  Crude  into  Malleable  Iron  — 
Various  Processes — Chemical  Reactions — Kind  of  Iron  most  suitable  for  Con- 
version— Variation  in  Quality — The  Puddling-furnace — Proce.ss  of  Paddling— 
The  Puddle-balls — Shingling  or  Blooming— Rolling-mills — Rolled  Armor- 
plates — Weldi  ng — U psett  i n g. 


Section  IV. — Steel. 

Peculiarities — Definitions — How  obiained  — Classification  — Process  of 
Cementation — Blister-steel  — Spring  steel  — Shear-steel  — Cast-steel  — Steel 
Ingots — Bessemer  Process — Annealing — Tempering  Steel  in  Oil. 

Section  V. — Bronze. 

Bronze  for  Cannon — Pure  Copper — Pure  Tin — Circumstances  affectin 
the  Production  of  Bronze — Constitution  of  the  Alloy — Difficulty  of  makin 
Sound  Castings. 


Section  VI. — General  Qualities. 

Qualities  necessary  in  Metals  for  Cannon — Properties  of  Metals — Density 
— Hardness — Brittleness — Tenacity — Porosity — Elasticity — Limit  of  Elasti- 
city— Permanent  Set — Malleability — DuctiliQv— Rupture — Qualities  of  Cast- 
iron — Qualities  of  Wrought  iron — Qualities  of  Steel — Qualities  of  Bronze. 


be  be 


VI 


CONTENTS. 


CHAPTER  II. 

GENERAL  DESCRIPTION  OF  ORDNANCE. 

Section,  I. — Terms  and  Definitions. 

Classification — Nomenclature — Interior  Form — Length  of  Bore — Wind- 
age— Seat  of  the  Charge — I'he  Vent — Exterior  Form — Force  to  be  restrained 
— Experiments — Devices — Mortars — Hcwitzers — Percussion  Lochs — The  Uai ■ 
ling  Gun. 


Section  II. — Theory  of  'Gun  Construction. 

The  Kinds  of  Strains  upon  a Gnn — Tangential  Strain — Longitudinal 
Strain  — Crushing- force — Transverse  Strain — Total  Bursting  Tendency — 
Determination  of  the  Exterior  JModel  of  Guns. 

Preponderance — To  determine  the  Preponderance — To  determine  the  Po- 
sition of  the  Trunnions — To  determine  the  Effect  on  the  Preponderance  of  a 
Change  in  the  Position  of  the  Trunnions. 


CHAPTER  III. 


CAST  GUNS. 

Section  I. — Standard  of  Iron. 

Smelting  of  Iron  for  Cannon — Difference  in  Quality — Effects  of  different 
Treatment — Practical  Treatment  in  Fusion — Tests  while  in  Fusion— Crys- 
tallization— Development  of  Crystals — Chilled  Castings — Effects  of  Crystalliza- 
tion on  Strength — Size  of  Crystals — Contraction  of  Casting — Effect  of  sudden 
Change  of  Form — Effect  of  Irregular  Cooling — Effect  of  Age  on  Endurance — 
Improvement  in  Casting — Standard  of  Quality — Comparison  with  Standard 
Samples — To  Determine  the  Density — The  Hydrometer — Wurdemann  Balance 
for  Specific  Gravities. 


Section  II. — Mechanical  Tests. 

The  Testing-machine — Capacity  of  the  Machine — Working  the  Machine 
— Adjusthients- -Tensile  Strain — Crushing-force — Errors  of  the  Machine — 
Modification  of  the  Machine. 

1 

Section  III. — Fabrication. 

Fabrication  of  Cast-iron  Guns — Charging  the  Furnace — Fusions — Mold- 
ing.?— Models— The  Flask — The  Core-barrel — The  Pit — Melting  D.own  the 
Charge — Tapping  the  Furnace — Cooling  the  Casting — Withdrawing  the  Core- 
barrel— Trimming  Down  the  Casting — Removing  the  Sinking-head — Cutting 
out  Specimens — Boring — Cutting  Hole  for  Elevating-screw — Drilling  the 
Vent — Marking  Guns — Fabrication  of  Bronze  Howitzers — The  Flask — Molding 
— The  Pit — Charging  the  Furnace— Melting  down  the  Charge — Casting. 

Section  IV. — Inspcciic  n . 

Inspection  of  New  Guns — The  Inspecting  Instruments — Vent  Impres- 
sions — Gutta-percha  Impressions — Powder-proof  — Water-proof — Extreme 
Proof  of  Trial  Guns — Enlargement  of  Vents — Endurance  of  Guns  in  Service 
— Injuries  from  the  Powder — Injuries  from  the  Projectiles — Descriptive  List 
of  Guns — Inspection  of,  at  Termination  of  a Cruise — Inspection  of  Vents. 


CO^'TE^^TS. 


Vi  I 


CHAPTER  IV. 
r-UILT-UP  GUXS.  . 

Section  I — Principles  of  Construction. 

DeSnitinni— Nature  of  the  Force  to  1)3  Restrained — Limit  of  Thickness  of 
Jtetal — Methods  of  Equallizing  the  Strain — System  of  Initial  Tension— De- 
fects of  the  System— Methods  of  Application — System  of  Varying  Elasticity — 
Defects  of  the  System. 

Section  IT. — The  Parrott  Gun. 

General  Description — The  Barrel — Tlio  Hoop — Placing  the  Reinforce. 


Section  III. — British  Guns. 

The  Armstrong  System — IMethod  of  Manufacture — The  Frazer  System — 
Tlie  "Woolwich  Gun — Details  of  Manufacture — Palliser  System  of  Conversion 
— Experimental  Guns — The  Wliitworth  Gun — The  Blakely  Gun — The  Vavas- 
seur  System. 

Section  IV. — French  Hatal  Guns. 


General  Description — Manner  of  Casting — Hoops — Breech-screw — Gas- 
check. 


Section  V. — Gernyin  Haval  Guns. 

Nomenclature — Features  of  tlie  Manufacture — The  Central  Tube — The 
Hoops — Breech-plug — Gas-chsck — Vent-tubs. 


CHAPTER  V. 

KIFLING. 

Section  I. — Principles. 

Definitions — Origin  of  Rifling — Introduction  of  Rifle-cannon — Progress 
in  Construction — Object  of  Rifling — Method  of  Rifling — Uniform  Twist — In- 
creasing Twist — Velocity  of  Rotation — Character  of  Grooves — Cutting  the 
Grooves. 


Section  II— Systems. 

Definitions — Classification — Centring — Wliitworth’s,  Vavasseur’s,  Scott’s, 
Lancaster's — Studs  or  Ribs  to  fit  the  Grooves — The  "Woolwich  System — The 
Shunt  System  — Expansion  System  — Parrott’s  — Compressing  Systems  — 
Krupp’s — Breech-loading. 

CHAPTER  VI. 

PROJECTILES. 

Section  I. — General  Description. 

Classification — Spherical  Projectiles — Elongated  Projectiles — Length — 
Form  of  Head — Studded  Projectiles — Expanding  Projectiles — Parrott’s— 
Dahlgren’s — Schenkla’s — Hotchkiss’ — Lead-coated  Projectiles — Solid  Projec- 
tiles— Hollow  Projectiles — -Shells — Case  Shot — -Shrapnel — Rifle- shrapnel — 
Grape-shot  — Canister — Htfie-canister — Fabrication  of  Projectiles  — Shot — 
Shell — Bouching— Chilled  Projectile.s— Steel  Projectiles — Inspection — Object 
— Condition  of  Loaded  Shell — Removing  Fuzes — Piling. 


CONTENTS. 


viii 


Section  II. — Deviation. 

General  Consideration  — Effect  of  Wind — Variable  Projectile  Force — 
Rotation  of  the  Earth — Faulty  Disposition  of  the  Line  of  Sio-]it — Influence  of 
tlie  State  of  the  Air — Deviation  of  Spherical  Projectiles — Windage — Eccen- 
tricity— Deviation  of  Elongated  Projectiles — Friction  against  the  Air — Centre 
of  Gravity — Couoidal-headed  Projectiles — Flat-headed  Projectiles — Drift. 


Section  III. — Effects. 

General  Consideration — Impact  of  Projectiles — Compression — Elongation 
— Shearing — Bending — Pulverizing — Friction — Heat — Penetration  — General 
Tlieory — Penetration  of  Spherical  Projectiles — Penetration  of  Elongated 
Projectiles — Formula  for  Penetration  of  Iron  Plates— Form  of  Head — Oblique 
Impact — Concussion — Armor-piercing  Projectiles— Shape — Spherical — Elong- 
ated— The  Effect  of  Hardening  Projectiles — Advantages  of  Steel  over  Chilled 
Projectiles — Experiments  against  Armor— Armor-plates  and  Backing — Wood 
Backing — Effects  on  Wood — Effects  on  Earth — Effects  on  Masonry — Punching 
and  Racking — Force  of  Imijact — The  Punching  Effects  of  Projectiles. 


CHAPTER  VII. 

GUN-CARRIAGES. 

Section  I. — United  States  Naval  Carriages. 

General  Considerations — Marsilly  Broadside-carriage — Pivot-carriages — 
Xl-inch  Iron  Pivot- carriage — 20-pdr.  Rifle  Pivot-carriage — XV-inch  Turret-car- 
riage— Mortar-carriage  — • Howitzer  Boat-carriage,  wood — Iron  Boat-carriage, 
Howitzer — Field-carriage. 


Section  II. — English  Naval  Carriages. 

The  Broadside  Scott  Carriage — Advantages  of  Mechanical  Carriages — 
High  and  Low  Carriages — The  Depression-carriage — The  Engli.sh  Turret-car- 
riage— The  Turret  Indicator — The  Moncrieff  System — Hydraulic  Appliances. 


CHAPTER  VIII.  , 

EXPLOSIVE  AGENTS. 

Section  I. — General  Consideration  of  E.rplosives. 

Definition — Explosive  Compounds — Explosive  Mixtures — Intensity  of 
Explosion — Detonation. 

Section  II. — Manufacture  of  Gunpowder. 

Ingredients  of  Gunpowder — Refining  Saltpetre — Description  of  the  Pro- 
cess— Solution — Filtering — Crystallization  — Washing  — Testing  — Drying — 
Extraction  of  Saltpetre  from  Damaged  Powder — Sulphur — Refining  Appara- 
tus— Process  of  Refining — Testing— — Converting  Wood  into  Char- 
coal— Effect  of  Temperature  Employed  in  Conversion — Qualities  of  Charcoal 
— Proportions  of  Ingredients — Preparing  and  Mixing  Ingredients — Incorpora- 
tion— Mill-cake — Pressing — Hniformity  of  Results — Graining — Dusting  and 
Glazing — Drying — Special  Powders — Explosion — Inflammation — Combustion. 


COXTEXTS. 


IX 


Section  Ill.—Inspection  of  Gunj)owder. 

General  Qualities — Examination  by  Hand — Flasbing — Size  of  Grain- 
Gravimetric  Density — Specific  Gravity — The  Mercury  Densimeter — Initial 
Velocity — ■ Ballistic  Pendulum  — Electro-ballistic  Machines — Xavez-Leurs 
Chronoscope— Benton's  Thread  Velociiiieter — Le  Boulenge’s  Chronograph — 
Schultz’  Chronoscope — Basht'orth’s  Chronograph — Noble’s  Chronoscope — Le 
Boulenge’s  Electric  Clepsydra — Strain  upon  the  Gun — Pressure  Gauges — 
Hygrometric  Qualities — Analysis — Marking  Barrels. 

Section  IV. — P reservation  of  Qui^ooicder. 

Magazines  on  Shore — Classification  of  Powder — Service  of  the  Magazine 
— Ships’  Magazines — Powder-tanks — System  of  Marking  Tanks — Service  of 
the  Magazine— Transportation  of  Powder. 

Section  V. — Explosive  Compounds. 

Gun-cotton  — Nitro-glycerine  — Uses — Compounds  of  Nitro-glycerine  — 
Dynamite — Lithofracteur — Dualiue — Fulminates. 

CHAPTER  IX. 

^ PYROTECHNT. 

Section  I. — Materials. 

Buildings — Classification  of  Materials — Compositions — Cases — Drifts. 

Section  II. — Means  of  Firing  Gannon. 

Percussion-primers — Friction -primers — Spur-tubes — Quick-match — Slow- 
match — Port-fires. 

Section  III. — Fuzes. 

Time-fuzes — Tlie  Navy  Time-fuze  — Times  of  Burning — To  Shorten 
Fuzes — Testing  Fuzes — Time-fuze  for  Rifle-prujectiles — Imperfection  of 
Time-fuzes — Premature  Explosion — The  Bormanu  Fuze — Concussion-fuzes 
— Percussion-fuze.s — Schenkle  Fuze — Parrott  Fuze — German  Percussion-fuze 
— Mortar-fuzes — Electric-fuzes. 

Section  IV. — Signals. 

Kinds — Signal  Rockets — C.osten  Signal-lights — Holders. 

Section  U. — Preparing  Ammunition. 

jVfeking  Cartridge-bags  — Filling  Cartridge-bags  — Service-charges  — 
Strapping  Shells — Filling  Shells  — Packing — Wads — Boat  Ammunition- 
Stand  of  Ammunition — Metallic  Cartridges — Incendiary  Preparations. 

CHAPTER  X. 

PR.\CTICE  OF  GtrXNERY. 

Section  I. — Service  of  Ordnance. 

Loading— Pointing — Sighting  Cannon— Tangent  Firing — Tangent  Sights 
— Adjustment  of  Sights — Marking  Sights— Determining  Distances — Use  of 
Plane-tables — Accuracy  of  Fire — The  Inclination  of  the  Target — Transferring 
R cord  of  Firing  from  Horizontal  to  Vertical  Target — Record  of  Target 
Practice  at  Sea — Elevating  Quoins  and  Screws. 


X 


CONTENTS. 


Section  II. — Different  Kinds  of  Fire. 

Classification— Direct  Fire— Ricociiet  Fire — Carved  Fire— Plunging  Fire 
— Solid-shot  Firing — Shell  Firing — Shrapnel  Firing — Grape  and  Canister 
Firing— Horizontal  Fire— Vertical  Fire— Falling  Velocity— Small-arm  Firing. 

Section  III. — Gun  Irnfflements. 

Staves — Sponges — Hammers — Ladleg — W orms — Sectional  Staves. 


CHAPTER  XI. 

TUE  JIOTION  OF  PROJECTILES. 

Equation  of  the  Path  of  a Projectile  in  a Non-resisting  Medium — To 
find  the  Time  of  Flight  of  a Projectile  on  a Horizontal  Plane — To  find  the 
Elevation  necessary  to  cause  the  Projectile  to  pass  through  a Point  given  by 
its  Co  ordinates — To  find  the  Velocity  of  a Projectile  at  any  Point  of  its 
Path — To  obtain  an  Expression  for  the  Direction  of  the  Path  at  any  Point — 
To  find  the  Co-ordinates  of  a Point  where  a Projectile  will  strike  an  In- 
<-lined  Plane,  passing  through  the  Point  of  Projection,  the  Range  on  the 
Inclined  Plane,  and  the  Time  of  Flight — Examples — The  Motion  of  a Projec- 
tile in  Air — Analytical  Expre.ssion  for  the  Cubic  Law  of  Resistance — Equation 
of  Motion  for  the  Cubic  Law  of  Resistance — Use  of  the  Tables — Examides — 
To  find  the  Range  on  a Horizontal  Plane — Law  of  Penetration  of  Projectiles. 


CHAPTER  XII. 

NAVAL  OPER.tTIONS  ON  SHORE. 

Section  I. — General  Considerations. 

Employment  of  a Naval  Force  on  Shore — The  Base — Preparations. 


Section  II. — Landing. 

Details — Equipment — The  Boats — Land!  ng. 

Section  III. — On  the  March. 

The  Advance — .\dvance  guard3— Rear-guards — Bivouac — Encampment — 
Guards. 

Section  IV. — Engaging. 

The  Attack — The  Skirmishers — The  Infantry — The  Artillery — The  De- 
fence. 

Section  V. — Field  Fortifications. 

Definitions — Plans — Profiles — To  Distribute  the  Workmen — Aj'tillery  in 
Eiehl-works — Defence  of  Walls — Defence  of  a Building — Defence  of  a 
Village — Defence  of  a Bridge — Attack  of  Works — Surprises — Open  Attack — 
Defence — Sorties. 

Section  VI. — The  Detreat. 

Rear  guards — Destruction  of  Bridges — Passage  of  a Defile — The  Em- 
barkation. 


LIST  OF  BOOKS  QUO'IFD. 


XI 


THE  FOELOWIXG  IS  A LIST  OF  THE  PRIXCTPAL  BOOKS  AND  DOCUMENTS 
• WHICH  HAVE  BEEN  CONSULTED  OR  QUOTED  IN  THIS  VOLUAIE 

A Course  of  Instruction  iR  Ordnance  and  Gunnery,  prepared  for  the  use  of 
tin;  Cadets  of  the  United  States  Military  Academy,  by  Brevet-Col.  J.  G. 
Benton,  Major  Ordnance  Department,  U.S.A.  ; late  Instructor  of  Ord- 
nance and  Science  of  Gunnery,  Military  Academy,  West  Point.  3d  edi- 
tion. (Kew  York  : D.  Van  IS'ostrand,  1867.) 

The  Principles  and  Practice  of  Ulodern  Artillery,  including  Artillery  Material. 
Gunnery,  and  Organization  and  Use  of  Artidery  in  Warfare.  By  Lieut. - 
Col.  (1.  n.  Owen,  B.A.,  Prof,  of  Artillery,  Koyal  Military  Academy, 
Woolwich.  (London  : John  Murray,  Albemarle  street,  1871.) 

A Text-hoolc  of  the  Construction  and  Manufacture  of  the  Pifled-ordnance  in  the 
BritiAi  Seroice.  ByCaptdnF.  S.  Stoney,  R.A.,  Asst.-Supt.  Royal  Gun 
Factories,  and  Lieut.  Charles  Jones,  R.A.,  Instructor,  Royal  Gun  Fac- 
tories. 

A Treatise  on  Ordnance  and  Armor,  embracing  Descriptions,  Discussions, 
and  Professional  Opinions  concerning  the  Material,  Fabrication,  Require- 
ments, Capabilities,  and  Endurance  of  European  and  American  Guns,  for 
Xaval,  Sea-coast,  and  Iron-clad  Warfare,  and  their  Rifling,  Projectiles, 
and  Breech-loading  ; also  results  of  Experiments  against  Armor.  By 
Alex.  L.  Holley.  (Xew  York  : D.  Van  Xostrand,  1865.) 

A Treatise  on  Ordnance  and  JTaixd  Gunnery.  Compiled  and  arranged  as  a 
Text-book  for  the  Ltnited  States  Xaval  Academy.  By  Lieut.  Edward 
Simpson,  U.  S.  Xavy.  (Xew  York  : D.  Van  Xostrand,  1863.) 

The  Artillerist's  Mmual.  Compiled  from  various  sources,  and  adapted  to  the 
Service  of  the  United  States.  By  Brig-Gen.  John  Gibbon,  U.  S.  Vols., 
Captain  4th  Artillery  U.  S.  Army.  2d  edition.  (Xew  York  : D.  Van 
Xostrand,  1863.) 

Gunnery  Instructions  U.  S.  Xavy.  Detail  Drill,  1870. 

A Treatise  on  the  M trdlurgy  of  Iron,  containing  Outlines  of  the  History  of 
Iron  Manuflicture,  Methods  of  Assay  and  Analyses  of  Iron  Ores.  Pro- 
cesses of  Manufacture  of  Iron  and  Steel.  By  H,  Bauerman,  F.G.S. 
(New  York  ; Virtue  & Yorston,  Dey  street,  1868.) 

Metals  : their  Prop'>rties  and  Treatment.  By  Charles  Loudon  Bloxam.  2d  edi- 
tion. (London  : Longmans,  Green  & Co.,  1871.) 

Ordnance  Instructions  for  the  United  States  Wavy.  Published  by  order  of  the 
Xavy  Dept.  (Washington  : Gov'ernment  Printing-office.) 

The  Ordnance  Manual,  for  the  use  of  the  Officers  of  the  U.  S.  Army.  (Phila- 
delphia : J.  B.  Lippincott  & Co.,  1861.) 

Ammunition.  A Descriptive  Treati.se  on  the  Different  Projectiles,  Charges^. 
Fuze,  Rockets,  etc.,  at  present  in  use  for  the  Land  and  Sea-service,  and 
on  other  War  Stores  manufactured  in  the  Royal  Laboratory.  By  Capt. 
V'^iviau  Dering  Majendie,  R. A.,  Asst.-Supt.  Royal  Laboratory,  Woolwich. 
(London  : W.  Mitchell  & Co.,  Military  Publishers,  39  Charing-cross,  1867  ) 

Part  I. 

Ammunition  for  Smooth-bore  Ordnance. 


LIST  OF  BOOKS  QUOTED. 


xil 


Pakt  II. 

Ammunition  for  Eified  Ordnance.  By  Captain  diaries  Orde  Brown,  R.A., 
Capt. -Instructor  Eoyal  Laboratory,  Woolwich.  , 

Part  II. — Continued. 

By  Capt.  C.  0.  Brown. 

d Treatise  on  JVaval  Gunnery.  Dedicated  by  special  permission  to  the  Lords 
Commissioners  of  the  Admiralty.  By  Gen.  Sir  Howard  Douglas,  Bart. 
5th  edition.  (London  : John  Murray,  Albemarle  street,  1860.) 

Shells  and  Shell  Guns.  By  J.  A.  Dahlgren,  Commander  in  Charge  of  Experi- 
mental Ordnance  Department,  Navy  Yard,  Washington.  (Philadelphia  : 
King  & Bird,  1857.) 

On  the  Physiced  Conditions  Involved  in  the  Construction  of  Artillery,  with  an 
Investigation  of  the  Relative  and  Absolute  Values  of  the  Materials  princi- 
pally employed,  and  some  hitherto  unexplained  Causes  of  the  Destruction 
of  Cannon  in  Service.  By  Robert  Mallet.  (London : Longman,  Prime, 
Green,  Longmans,  & Roberts,  1856.) 

Reports  of  Experiments  on  the  Properties  of  Metals  for  Cannon,  and  the 
Qualities  of  CcLhnun  Powder,  with  an  Account  of  the-  Fabrication  and 
Trial  of  a 15-iuch  Gun.  By  Capt.  T.  J.  Rodman,  of  the  Ordnance  De- 
partment U.  S.  Army.  (Boston  : Charles  H.  Crosby,  1861.) 

Reports  of  Experiments  on  the  Strength  and  other  Properties  of  Metals  for 
Cannon,  with  a Description  of  the  Machines  for  testing  Metals,  and  of 
the  Classification  of  Cannon  in  Servdee.  By  Officers  of  the  Ordnance  De- 
partment U.  S.  Army.  (Philadelphia  : Henry  Carey  Baird,  1856.) 

Report  on  the  Fabrication  of  Iron  for  Defensive  Purposes,  and  its  use  in 
Modern  Fortifications,  especially  in  Works  of  Coast  Defence.  Professional 
Papers  of  the  Corps  of  Engineers  LI.  S.  Army.  No.  21.  (Washington  : 
Government  Printing-offices,  1871.) 

Report  on  Certain  Experimented  and  Theoretical  Investigations  relative  to  the 
Quality,  Form,  and  Combination  of  Materials  for  Defeeisive  Armor, 
together  with  Incidental  Facts  relative  to  their  use  for  Industrial  Pur- 
poses. By  Brevet-Major  W.  R.  King,  Capt.  of  Engineers,  U.  S.  Army. 
(Washington  : Government  Printing-office,  1870.)  Professional  Papers 
Corps  of  Engineers  U.  S.  Army.  No,  17. 

A Manual  of  Gunnery  for  Her  Majesty’s  Fleet.  Corrected  up  to  1st  Januarv, 
1872.) 

The  Le  Boadenge  Chronograph.  By  Brevet-Capt.  O.  E.  Michaelis,  First  Lieut. 
Ord. -Corps  U.  S.  Army.  (New-York  : D.  Van  Nostrand,  1872.) 

Traite  cVArtillerie  Theorique  et  Pratique.  Par  G.  Piobert.  (Paris  : Gauthier 
1869.) 

Electro-ballistic  Machines  and  the  Schidtze  Chronoscope.  By  Brevet  Lieut. - 
Col.  S.  V.  Benet,  Capt.  of  Ordnance  U.  S.  Army.  (New  York  : D.  Van 
Nostrand,  1866.) 

Holes  on  Gunpowder,  prepared  for  the  use  of  the  Gentlemen  Cadets  of  the  Royal 
Military  Academy.  By  Capt.  Goodenough,  R.A. , Instructor  in  Artillery, 
Royal  Military  Academy.  (London  ; Mitchell  & Co.,  Charing-cross,  1868.) 

Ure’s  Dictionary  of  Arts,  Manufactures,  and  Mines.  Edited  by  Robert  Hunt, 
F.R.S.  6tii  edition.  (London  : Longmans,  Green  & Co.,  1867.) 


LIST  OF  BOOKS  QUOTED. 


xiii 

Journals  of  the  Royal  United  Service  Institution.  (London  : W.  Mitcliell  & 
Co.,  Charing- cross.) 

Inspection  and  Proof  of  Cannon  for  the  United  States  Navy.  (Washington  : 
Government  Printing-office,  1804.) 

United  Stales  Navy  Gunnery  Notes.  (Washington  : Government  Printing- 
office,  1871.) 

United  States  Navy  Laboratory  Notes.  (Washington  : Government  Printing- 
office,  1871.) 

Gunpoinder  as  an  Mement  in  the  Problem  of  Modern  Ordnance,  the  Influence 
ot  Density  on  its  Explosive  Action,  and  the  Densimeter  it  uses,  and  Ad- 
justments. Naval  Ordnance  Papers  No.  1.  By  Lieut. -Commander  J.  D. 
Marvin,  U.  S.  N.  (Washington  : Government  Printing-office,  1872.) 

Mode  of  Fabricating  the  XV.-in.  Guns  contracted  for  by  the  Chief  of  the  Bureau 
of  Ordnance,  Navy  Department,  with  the  “ Knap  Fort  Pitt  Foundry,  ’ 
Pittsburg,  Pa.,  1870  and  1871.  Naval  Ordnance  Papers  No.  3.  By  Com- 
mander R.  F.  Bradford,  U.  S.  N.  (Washington  : Government  Printing- 
office,  1872.) 

A Concise  Treatise  on  the  Theory  and  Practice  of  Naval  Gunnery.  By  M'in. 
N.  Jeffers,  Jr.,  passed  Midshipman  U.  S.  Nav3^  (New  York  : D.  Apple- 
ton  & Co.) 

Recent  Investigations  and  Applications  of  Explosive  Agents.  By  F.  A.  Abel, 
F.R.S.  (Washington  : Government  Printing-office,  1871.) 

A Mathematical  Treatise  on  the  Motion  of  Projectiles.  By  Francis  Bashforth, 
Prof.  Mathematics,  Woolwich.  (London  : Asher  & Co.,  13  Bedford  Street' 
Covent  Garden,  W.C. , 1873.) 

Nicaise’s  Belguin  Field  Artillery.  Translated  with  an  Appendix  and  Notes, 
by  0.  E.  Michaelis,  Cap.  Ordnance  U.  S.  A.  (W.  C.  & F.  P.  Church' 
New  York,  1872.) 

American  Breech-loading  Small-arrhs.  A Description  of  late  Inventions,  in- 
cluding the  Gatling  Gun,  and  a Chapter  on  Cartridges.  Compiled 
by  Brig. -Gen.  C.  B.  Norton,  U.  S.  Vols.  (New  York  : F.  W.  Christeru, 
77  University  place,  1872.) 

Instructions  for  Officers  and  Non-Commissioned,  Officers  on  Outpost  and  Patrol 
Duty.  Authorized  and  adopted  by  the  Secretarv  of  War.  (Philadelphia  : 
J.  B.  Lippincott  & Co.,  1863.) 

Practiced  Treatise  on  Strengthening  and  Defending  Outpost  Villages,  Houses, 
Bridges,  etc.  By  J.  Jebb,  Lieut. -Col.,  Corps  Royal  Engineers.  3d  edi- 
tion. (London  : W.  Clowes  & Sous.) 

An  Elementary  Course  of  Military  Engineering — Part  I.  Comprising  Fixed 
Fortifications,  Military,  Mining,  and  Siege  Operations.  By  D.  H.'iMahan, 
LL.D.,  Prof.  Military  and  Civil  Engineering,  U.  S.  Military  Academv' 
(New  York  : John  Wiley  & Sou,  1806.) 

The  Soldier's  Pocket-book  for  Field  Service.  By  Col.  G.  J.  Wolseley,  Deputy 
Quartermdster-Geueral  in  Canada.  (London:  MacMillan  & Co'.,  1869.)  ' 

Comp  and  Outpost  Duty  for  Infantry  with  Standing  Orders.  Extracts  from 
the  Revised  Regulations  for  the  Armv,  Rules  for  Health,  Maxims  f..r 
Soldiers  and  Duties  of  Officers.  By  Daniel  Butterfield,  Mai  -Gen  U S 
Vols.  (New  York  : Harper  & Brothers,  1863.) 


XIV 


LIST  OF  BOOKS  QUOTED. 


Report  to  the  Government  of  the  United  States  on  the  Munitions  of  War  ex- 
hibited at  the  Paris  Universal  Exhibition,  1807.  By  Chas.  B.  Xorton, 
late  Lieut. -Colonel  U.  S.  Vols.,  and  \V.  J.  Valentine,  Esq.,  President  of 
U.  S.  Com.,  1855,  United  States  Commissioners.  (Xew-York  : Office  ot 
Army  and  Navy  Journal,  39  Park  row,  1868.1 

{Jhemieal  Phenomena  of  Iron  Smelting.  An  Experimental  and  Practical  Ex- 
amination of  the  Circumstances  which  determine  the  Capacity  of  the 
Blast-furnace,  Temperature  of  the  Air,  and  the  proper  Condition  of  the 
Material  to  be  operated  upon.  Bj^  J.  Lowthian  Bell.  (New  York  : D.  Van 
Nostrand,  23  Murray  street,  1872.) 

Boat  Armament  of  the  United  Slates  Navy.  Designed  by  and  executed  under 
the  direction  of  J.  A.  Dahlgren,  Commander  U.  S.  N.  in  Charge  of  the 
Ordnance  Department,  U.  S.  Navy  Yard,  ^Vashington,  D.  C.  2d  edition. 
(Philadelphia  : King  & Baird,  1850.) 

The  Management  of  Steel.  By  George  Ede,  employed  at  the  Royal  Gun 
Factories  Department,  Woolwich  Arsenal.  (New  York  : D.  Appleton  & 
Co.,  1867.) 

Dictionnaire  vies  Matliematiqu'es  AppUquees.  Par  H.  Sonnet.  (Paris  : Libraire 
de  L.  Hacliette  et  Cie.,  Boulevard  Saint-Germain,  No.  77,  1807.; 

Report  on  a Naval  Mission  to  Europe.  Especially  devoted  to  the  Material  and 
Construction  of  Artillery.  By  Captain  E.  Simpson,  U.  S.  N.  2 vols. 
(Washington:  Government  Printing-office,  1873.) 

Annual  Report  of  the  Chief  of  Ordnance  to  the  Secretary  of  War,  for  the 
years  1872  and  1873,  (Washington  : Government  Printing-office.) 

Spans’  Dictionary  of  Engineering  : Civil,  Mechanical,  Military,  and  Naval. 
Oliver  Byrne,  editor.  (Loudon  : E.  & F.  N.  Spon,  48  Charing-cross, 
1873.) 

A Handbook  of  the  Manufacture  and  Proof  of  Gunpoicdcr  as  carried  on  at 
the  Royal  Gunpowder  Factory,  Walth.un  Abbey.  By  Capt.  F.  M.  Smitli, 
R.A.,  Assistaut-Saperintendent.  (L.mdon,  1870.) 

Instructions  for  the  Care  and  Preparettion  of  Ammunition.  (Published  by 
the  United  States  Naval  Ordnance  Bureau,  1874.) 

The  Determination  of  the  Time  of  Flight  of  Projectiles,  etc.,  by  Means  of  the 
Electric  Clepsydra,  from  Researches  in  Experimental  Ballistics.  By  .\iajor 
P.  Le  Boulenge,  Belgian  Artillery.  Translated  from  the  French  by 
Lieut. -Commander  J.  D.  Marvin,  U.  S.  Navy.  (Washington  : Govern- 
ment Printing-office,  1873.) 

United  States  Naval  Ordnance  Notes. 


The  Reffye  Gun.  1873. 


MYAL  ORDNANCE  AND  GUNNERY. 


CHAPTER  I. 

CANNON  METALS. 

Section  I — Metallurgy  of  Iron. 

1.  Metallurgy  of  Iron  * is  the  art  of  extracting  iron 
from  its  ores.  This  metal  is  nsed  in  the  mannfaeture  of  most 
of  the  engines  of  destruction  that  modern  science  has  intro- 
duced into  the  art  of  war.  In  its  pure  state  it  is  rarely  found 
in  nature,  hut  its  ores  exist  in  great  abundance  in  all  parts  of 
the  world. 

The  natural  compounds  of  iron  which  are  available  as  ores 
of  the  metal,  are  chiefly  oxides  and  carbonates.  These  scarcely 
ever  occur  in  a state  of  purity,  but  associated  with  clay  and 
other  silicious  minerals,  or  with  limestone,  which  substances 
are  useful  as  slag-forming  components;  and  also  with  com- 
pounds of  sulphur  and  phosphorus,  which  are  deleterious  im- 
purities. 

2.  PEEPAEATIOlSr  OF  IEOH  ORES.— The  ironstone, 
or  ores  of  iron,  w'hen  extracted  from  the  mines,  being  in  a 
very  rough  state,  and  intermixed  with  earthy  substances,  it  is 
first  necessary  to  prepare  them  for  the  Ijlast  or  smelting  fur- 
nace. 

Ores  are  subjected  to  different  treatment  in  different  coun- 
tries and  at  different  mines,  depending  upon  their  value  and 
quality. 

3.  Dressing. — Some  ores  are  not  subjected  to  any  partic- 
ular dressing,  while  others  are  separated  from  a portion  of  the 
intermingled  clay  and  sand  by  sifting,  crushing,  stamping  and 
washing. 

* B.auerman. 


1 


2 


NAVAL  ORDNANCE  AND  GUNNERY. 


These  processes  are  usually  accomplished  hy  breaking- 
machinery  and  roller-crushing-mills.  The  machinery  used  for 
washing  the  ores  generally  consists  of  a horizontal  staff  armed 
with  projecting  knives  or  paddles,  revolving  in  a cylindrical 
trough,  through  which  a stream  of  Avater  is  kept  flowing.  The 
rough  ore,  after  being  well  mixed  up  Avith  the  Avater  by  the 
action  of  the  paddles,  is  carried  by  the  stream  into  a settling- 
pit,  where  the  heavier  masses  of  clean  ore  deposit,  while  the 
flnely  divided  earthy  matter  is  carried  off  with  the  Avaste  water. 

Washing  of  ores  is  rarely  practised,  except  in  countries 
where  labor  is  very  cheap,  or  facilities  for  waslaing  very  great. 

4.  Weathering. — At  some  mines  the  ores  are  exposed  to 
the  action  of  the  air  for  some  time.  Superflcial  oxydation 
takes  place,  the  adherent  fragments  of  foreign  substances 
disintegrate,  and  can  be  readily  removed ; and  impurities  are 
also  partially  removed  by  rain. 

5.  Ironstone  Breakers. — In  order  to  attain  the  greatest 
regularity  in  the  process  of  smelting,  it  is  advisable  that  all 
charges  of  ores  and  fluxes  should  be  reduced  to  fragments  of 
nearly  uniform  dimensions.  The  size  of  the  fragments  should 
be  proportioned  to  the  height  of  the  furnace  and  the  greater 
or  less  susceptibility  to  reduction  of  the  ore,  varying  from 
cubes  of  one  to  two  inches  in  the  side,  to  as  ranch  as  four  to 
six  inches  in  the  side.  The  limits  are  determined  by  the  con- 
ditions required  : the  larger  masses  being  only  adapted  for  tall 
furnaces,  Avhen  by  the  sIoav  descent  of  the  charges,  suflicient 
time  is  allowed  for  the  heat  to  penetrate  to  the  interior,  at  the 
same  time  that  a free  passage  is  afforded  to  the  upper  curi-ent 
of  the  gas.  Smaller  pieces,  on  the  other  hand,  although  expos- 
ing a greater  surface  to  the  action  of  the  reducing  gases,  pack 
closer  together  and  offer  greater  resistance  to  the  blast. 

The  reduction  in  size  is  effected  by  various  mechanical 
means  of  breaking,  the  most  advantageous  of  which  arc 
crushing^ollers  and  lever-machines  called  h'reakers.  The  ma- 
terial operated  upon  is  sometimes  raw  ore  and  sometimes 
Avashed  ore. 

6.  Roasting  or  Calcination  of  Iron  Ores. — In  this  coun- 
try roasting  of  ores  is  much  less  practised  than  in  England  and 
on  the  Continent ; partly  on  account  of  the  higher  price  of 
labor  here,  but  chiefly  because  our  principal  ores — hematites 
and  magnetites — are  anhydrous. 

The  object  of  roasting  is  to  expel  the  Avater,  sulphur,  arse- 
nic and  other  impurities  AAotli  Avhich  the  ores  are  combined ; 
all  volatile  matters  are  thus  remoA'ed,  the  amount  of  iron  is 
concentrated  into  a smaller  weight,  and  as  the  fragments  of 


CANNON  METALS. 


3 


mineral  retain  their  form  they  are  rendered  porous  and  more 
readily  susceptible  of  being  changed  in  the  subsequent  opera- 
tions in  the  smelting-furnace.  The  roasting  is  eUected  in 
various  ways,  which  may  be  classified  generally  under  two  dif- 
ferent heads. 

7.  First.  Roasting  in  the  Open  Air. — This  is  done  by  dis- 
tributing the  ore  in  alternate  layers  with  waste  coal,  wood  or 
charcoal,  and  the  pile  tlius  formed  is  igTiited  and  burned.  This 
anethod  is  used  in  localities  where  fuel  is  cheap,  when  compared 
with  labor,  but  is  in  many  respects  disadvantageous  on  account 
of  the  waste  of  fuel  and  the  imperfect  distribution  of  the  heat, 
the  interior  of  the  pile  often  being  heated  to  excess,  with  a 
partial  fusion  of  the  ore,  when  the  outer  parts  have  only  at- 
tained the  proper  temperature. 

8.  Second.  Roasting  in  Furnaces  or  Kilns. — This  method 
is  generally  to  be  preferred  when  economy  of  fuel  is  of  impor- 
tance, as  the  heat  of  combustion  is  more  perfectly  applied,  and 
a more  uniform  product  is  obtained,  than  is  the  case  with  the 
more  rude  method  of  roasting  in  the  air. 

The  construction  of  the  kilns  in  different  localities  varies 
considerably,  but  the  principle  of  working  is,  in  the  main,  the 
same  everywhere. 

The  ore  is  piled  above  a thin  bed  of  fuel  at  the  bottom  of 
the  kiln  shaft,  which  may  be  conical,  cylindrical,  barrel  or 
wedge  shaped,  and  when  ignited  is  covered  with  layers  of  ore 
and  fuel  alternately  until  the  shaft  is  full  to  the  top  or  throat. 

The  ore  roasted  by  the  combustion 
of  the  fuel  at  the  bottom,  where  the  air 
has  access  to  the  kiln,  is  withdraAvn,  and 
the  next  layer  falls  ; the  deficiency  be- 
ing made  good  by  fresh  charges  at  the 
tojx  (Fig.  1.) 

9.  SMELTTMG  is  the  process  by 
which  the  iron  is  reduced  to  the  metal- 
lic state,  and  separated  from  the  refrac- 
tory substances  with  which  it  is  com- 
bined in  the  ore. 

It  consists  in  raising  the  ore  to  a 
high  heat,  in  contact  with  carbon  and  a suitable  flax,  in  the 
blast  or  smelting  furnace.  The  flux  unites  with  the  earthy 
matter  of  the  ore,  forming  a glassy  substance  called  slag  or 
cinder,  and  the  carbon  as  carbonic  oxide  unites  with  the  oxy- 
gen of  the  ore,  setting  the  iron  free ; which  in  turn  unites  with 
a portion  of  the  carbon  and  forms  a fusible  compound  called 
pig  or  cast-iron. 


Fig.  1. 


4 


NAVAL  OEDNANCE  AND  GUNVSTEEY. 


10.  Fluxes  used  in  Ieon-smelting. — Tn  practice,  very  few 
ores  are  found  to  contain  earthy  ingredients  in  proportions  suf- 
ficient to  form  readily  fusible  slags  alone,  and  it  therefore  be- 
comes necessary  to  supply  the  deficiency.  This  may  be  done, 
either  by  mixing  ores  of  dissimilar  composition  in  such  quanti- 
ties as  shall  yield  slags  of  the  desired  composition,  or  by  the 
addition  of  calcareous  or  aluminous  minerals  not  containins^ 

O 

iron. 

The  first  of  these  methods  is  certainly  to  be  preferred,  as 
by  it  the  slag  is  formed  without  unnecessarily  reducing  the 
percentage  of  iron  in  the  charge  or  burden,  taken  as  a whole : 
whereas,  the  addition  of  fluxes  increases  the  weight  of  material 
to  be  passed  through  the  furnace  for  the  same  produce  of 
metal ; but  it  can  only  be  carried  out  in  localities  having  a 
large  and  varied  command  of  minerals.  Usually,  therefore,  a 
combination  of  both  methods  is  used,  the  best  mixture  of  ores 
obtainable  being  supplemented  by  the  addition  of  earthy  min- 
erals. 

11.  Difficulty  of  Obtaining  Puee  Metal. — The  reduction 
of  iron  ores  can  be  effected  practically  only  by  carbon  or  car- 
bonic oxide. 

The  ]UTneipal  flux  employed  in  iron  smelting  is  carbonate 
of  lime  in  the  form  of  limestone.  As  a very  high  temper- 
ature is  necessary  to  effect  the  reduction,  the  metal  almost 
always  combines  with  a greater  or  less  proportion  of  the  reduc- 
ing agent,  as  well  as  of  other  elementary  substances;  such  as 
silicon,  sulphur  and  phosphorus,  that  may  be  present  either  in 
the  ore,  the  fuel  or  the  flux ; so  that  the  ultimate  result  is  never 
a pure  metal,  but  a compound  of  iron  with  carbon,  silicon,  sul- 
phur, phosphorus  and  sometimes  manganese,  and  occasionally 
traces  of  other  baser  elements,  as  titanium,  etc. 

Small  traces  of  foreign  elements  exert  a very  marked  influ- 
ence on  the  metal,  and  it  is  these  small  and  in  many  cases 
unnoticed  differences  of  composition,  that  render  so  many 
points  in  the  chemistry  and  practical  working  of  iron  obscure 
and  difficult  to  be  understood. 

12.  Composition  of  Fluxes. — The  composition  of  the  lime- 
stone to  be  used  is  of  considerable  importance,  and  depends 
upon  the  kind  of  ores  employed.  Chemical  analysis  alone  can 
determine  to  which  class  a particular  limestone  belongs,  as 
there  is  often  nothing  in  the  external  appearance  by  which  a 
pure  limestone  may  be  distinguished  from  one  containing  forty 
or  fifty  per  cent,  of  foreign  matter.  Magnesium  limes'tone  is 
especially  to  be  avoided  as  producing  a very  refractory  slag. 

The  addition  of  fluxes  to  the  blast-furnace  is  regulated  by 


CANNON  METALS. 


5 


several  considerations.  When  the  ores  are  of  good  quality,  the 
chief  point  to  be  considered  is  the  production  of  the  most  fusi- 
ble slag,  with  the  smallest  addition  of  non-ferriferous  matters ; 
this  is  more  especially  the  case  with  charcoal-furnaces.  When 
mineral  fuel  is  used,  however,  it  is  necessary  to  form  a slag 
that  is  capable  of  absorbing  sulphur,  which  would  otherwise  be 
taken  up  by  the  iron  ; and,  for  this  purpose,  a larger  quantity  of 
flux  is  used  than  that  indicated  by  theory,  as  giving  the  most 
fusible  product.  The  quality  of  the  iron  produced,  depends 
greatly  upon  the  kind  of  flux  employed. 

13.  Slag  is  the  vitreous  mass  wdiich  covers  the  fused  metal 
in  the  smelting-hearth.  It  is  commonly  called  cinder. 

The  physical  character  of  slag,  such  as  color,  texture,  fluid- 
ity, etc.,  varies  with  the  composition  and  the  working  condition 
of  the  furnace,  so  that  it  is  not  possible  from  inspection  alone, 
to  determine  the 
character  of  the 
metal  produced, 
except  after  con- 
siderable experi- 
ence of  the  in- 
dividual furnace ; 
and  the  relation 
between  the  slag 


and  metal  in  one 
locality  may  be  to- 
tally different  in 
another. 

II.  Fuel.  — 

The  fuel  used  in 
iron-smelting  va- 
ries in  dilferent 
localities  and  with 
the  purposes  for 
wdiich  the  iron  is 
intended.  Char- 
coal is  said  to 
make  the  most  su- 
perior iron,  and  is 
always  used  in  the 
manufacture  of 
iron  for  ordnance 
purposes.  Coke 
is  very  generally 

used,  and  bituminous  and  anthracite  coals  are  also  employed. 


Fig.  2. — Blast-fumace  for  Smelting  Iron  Ores. 


6 


NAVAL  ORDNANCE  AND  GUNNERY. 


15.  THE  BLAST-FURlSrACE. — The  means  of  reducin'? 
iron  ore  now  almost  universally  in  use,  is  the  blast  or  smelting 
furnace.  (Fig.  2.) 

CoNSTEDCTioN. — This  consists  mainly  of  a tall  shaft  of  brick 
and  stone  or  of  iron,  and  generally  of  the  form  of  a truncated 
pyramid,  but  sometimes  cylindrical  or  rectangular. 

The,  construction  of  blast-furnaces  varies  considerably  in 
different  localities  in  regard  to  size  and  proportions  of  parts  to 
each  other,  as  well  as  material  employed. 

The  height  and  dimensions  vary  with  the  nature  of  the  ores 
and  fuel  used. 

16.  The  Stacli. — The  interior  has  the  forai  of  two  trun- 
cated cones,  united  at  their  bases.  The  upper  one,  C,  which  is 
the  larger  and  more  acute,  is  placed  upright ; it  constitutes  the 
furnace  proper,  and  is  knoAvn  as  the  stach. 

17.  The  Boshes.— lower  cone,  B,  which  is  inverted,  is 
shorter  and  more  obtuse  than  the  other;  their  line  of  junction 
forming  the  widest  part  of  the  furnace.  A,  is  called  the  hashes, 
and  it  terminates  below  in  a space  called  the  hearth,  E. 

18.  The  Hearth. — The  hearth,  properly  speaking,  is  that 
part  of  the  furnace  only  which  receives  the  fluid  metal  and  cin- 
der as  they  fall  'below  the  level  of  the  twyers,  o. 

Three  of  the  sides  of  the  hearth  descend  to  the  bottom  of 
the  furnace,  or  to  the  hearth-stone,  while  the  fourth  side,  called 
the  tymp,  t,  does  not  go  all  the  way  down,  but  leaves  an  open- 
ing, and  is  supported  by  an  arch  or  by  strong  bars  of  iron  let 
into  the  sides  of  the  furnace. 

19.  Furnace-lining. — The  interior  of  the  furnace  has  a 
double  lining  of  fire-brick,  i,  I,  the  space  between  them  being 
tilled  with  sand  or  broken  slag  to  prevent  injury  to  the  outer 
wall  by  the  expansion  of  the  lining  from  the  heat.  The  hearth 
and  hearth-stone  and  boshes  are  built  of  refractory  material 
because  of  the  great  heat  which  they  have  to  endure. 

20.  Details  of  the  lower  Part  of  the  Furnace. — Arched 
openings  ar-c  built  on  each  side  of  the  shaft  at  the  bottom,  three 
of  which  are  called  the  twyer-arches,  and  the  other  the  tymp- 
arch. 

21.  The  Twyers,  or  blast-pipes,  are  the  ends  of  the  pipes 
through  which  the  blast  is  admitted  to 
the  hearth,  and  as  they  are  exposed  to 
a high  temperature,  they  are  east  so  as 
to  enclose  a coil  of  wrought-iron  tubes, 
through  which  a stream  of  cold  water 
continually  circulates.  Fig.  3 represents 
a section  of  a twyer-nozzle  thus  protected,  the  cold  water  en- 


CANNON  METALS. 


7 


tei’ing  the  casing  by  the  tube  and  the  hot  water  running  off 
by  the  tube  t' . 

22.  Twyer-lioles. — Passages  for  the  introduction  of  these 
])ipes  are  perforated  through  the  wall  of  the  hearth,  o,  a short 
distance  above  the  hearth-stone.  These  are  known  as  twyer- 
holes,  and  vary  in  number. 

The  smaller  charcoal-furnaces  have  often  only  two,  placed  on 
opposite  sides  of  the  hearth.  Three  is  a more  usual  number,  one 
leing  placed  at  the  back,  opposite  to  the  tymp,  and  the  others 
at  the  sides  of  the  hearth.  When  a larger  number  is  used  they 
are  generally  placed  at  equal  intervals  all  around  the  hearth. 

23.  The  Fore-hearth  is  the  front  or  working  side  of  the 
hearth.  This  side  is  constructed  difPerently  from  the  others, 
its  upper  part  being 
formed  by  a heavy 
block  of  stone,  g 
(Fig.  4),  called  the 
tymp-stone,  which  is 
supported  by  a east- 
iron  tymp-plate, 
built  into  the  mason- 
ry of  the  furnace ; 
while  the  lower  part 
is  enclosed  by  the 
dam-stone,  b,  faced 
externally  by  a thick 
cast-iron  dam-plate, 
m.  That  portion  of 
the  hearth  which  is 
shut  in  by  the  dam-stone  is  called  the  oricchble,  for  it  is  here 
that  the  cast-iron  produced  in  the  furnace  accumulates  in  a 
melted  state  covered  with  slag. 

24.  The  Cinder-notch. — A semi-circular  furrow  in  the  top 
edge  of  the  dam,  known  as  the  cinder-notch,  forms  a passage  for 
the  slag.  In  charcoal  and  other  small  furnaces  the  front  of  the 
dam  is  generally  formed  into  a gently  sloping,  inclined  plane,  or 
cinder-fall,  where  the  slag,  as  it  runs  out,  solidities  in  a compara- 
tively thin  layer,  and  may  be  broken  up  and  removed  by  hand. 

25.  Tap-hole. — The  tap-hole  for  withdrawing  the  molten 
iron  from  the  hearth  is  a narrow  vertical  slit  pierced  through 
the  darn,  and  extending  from  the  hearth-stone  upwards.  Dur- 
ing the  time  that  the  hearth  is  tilling  it  is  stopped  by  a pack- 
ing of  sand,  rammed  iia  tight,  which  can  be  easily  perforated 
by  a pointed  bar  at  the  time  of  casting. 

20.  Tymp-stopping. — The  space  between  the  top  of  the 


8 


NAVAL  ORDNANCE  AND  GUNNERY. 


dam  and  the  tymp-stone  is  also  stopped  with  sand  or  brick,  a 
small  passage  being  left  for  the  escape  of  slag ; this  is  called 
the  tymp-stopping. 

27.  Details  of  the  Top  of  the  Furhace. — The  top,  or 
throat,  of  the  furnace  is  surrounded  by  a platform  for  the  con- 
venience of  charging,  and  is  in  many  cases  covered  with  a . 
short  cylindrical  chimney  which  leads  off  the  flame  escaping  at 
the  throat,  F.  (Fig.  2.) 

28.  Throat,  Cup,  and  Cone. — When  it  is  desired  to  collect 
the  gases  given  off  at  the  top  of  the  furnace,  it  is  necessary  to 
work  with  a closed  throat. 

The  most  simple  contrivance  for  this  purpose,  and  that  most 
generally  used,  is  known  as  the  cup  and  cone.  (Fig.  5.)  It  con- 
sists of  an  in- 
verted, conical 
cast  - iron  fun- 
nel, A,  fixed  to 
the  top  of  the 
furnace,  whose 
lower  aperture 
is  of  about  one- 
Iialf  the  diam- 
eter of  the 
throat. 

An  upright 
cast-iron  cone, 

B,  is  placed  in 
the  furnace  be- 
low the  cup  ; it 
is  suspended  by 
a chain  attached 
to  its  apex,  so 

that  it  may  he,  raised  or  lowered  at  pleasure.  In  the  former 
position  it  hears  against  the  bottom  of  the  cup  and  forms  an 
air-tight  stopper,  preventing  the  escape  of  gas  from  the  top  of 
the  furnace  ; which  then  finds  its  way  out  by  the  proper  passage 
through  the  wall  of  the  furnace,  C. 

29.  How  suspended. — The  cone  is  suspended  by  an  arch- 
headed lever,  carrying  a counterbalance  at  the  end  of  the  op- 
posite arm. 

The  raising  or  lowering  is  effected  by  a pinion  moved  by  a 
hand-wheel  gearing  into  a ratchet  attached  to  the  counter-bal- 
ance weight.  The  gas  passes  through  a lateral  flue  into  a 
wrought-! ron  main-pipe,  which  distributes  it  to  the  various 
pipes  feeding  the  boiler  fires  and  hot-blast  stoves. 


Fig.  5. — Cup  and  Cone  for  closing  the  Blast-furnace, 
in  order  that  the  waste  gases  may  pass  into  the  lat- 
eral tlue,  as  shown  by  the  arrow. 


CAXJfOJir  METALS. 


9 


30.  Chaeging. — The  charges  are  thrown  into  the  space 
enclosed  by  the  cup,  then  by  lowering  the  cone,  it  allows  the 
charges  in  the  cup  to  be  dropped  into  the  furnace  and  at  tlie 
same  time  acts  as  a distributer  ; only  the  small  amount  of  gas 
that  is  lost  during  the  time  of  charging  is  allowed  to  escape, 
and  as  the  operation  is  very  quickly  performed  the  current 
through  the  main-pipe  is  kept  up  with  great  regular] tju 

31.  The  Blast,  or  draft,  in  the  furnace  is  iutroduced 
through  the  twyers,  and  is  maintained  by  means  of  blowing- 
engines  of  various  constructions. 

32.  Pressure  of  Blast . — The  working-limits  of  blast-press- 
ure vary  with  the  nature  of  the  fuel  employed,  and  the  burden 
of  the  furnace,  etc. 

A steady  current  in  the  furnace  is  accomplished  by  arrange- 
ments for  equalizing  the  pressure,  and  its  amount  and  force 
are  indicated  by  means  of  gauges. 

33.  Tejipekatuee  of  Blast. — How  Determined. — In  prac- 
tice the  temperature  of  the  blast  is  generally  determined  by  its 
power  of  fusing  metals,  mercurial  thermometers  not  being  reli- 
able for  temperatures  much  above  400°  or  500°  F.-,  owing  to 
the  irregular  expansion  of  the  mercury  when  near  its  boiling- 
point.  This  is  done  by  exposing  a thin  rod  of  the  metal  to 
the  current  in  the  twyer,  a hole  being  made  for  the  purpose  in 
the  elbow  of  the  branch-pipe  connecting  the  twyer  with  the 
main  blast- pipe. 

34.  The  following  table,  from  “ Bloxam  on  Metals f con- 
tains the  melting  points  of  various  metals : 


TABLE  OF  FUSEBmiTY. 


Tin  melts  at 442°  F. 

Cadmium  “ “ 442°  “ 

Bismuth  “ “ 507°  “ 

Lead  “ “ 617°  “ 

Zinc  “ “ 773°  “ 

Antimony*  “ “ 1,150°  “ 

Silver  “ “ 1,800°  “ 

Copper  “ “ 1,990°  “ 

Gold  “ “ 2,000°  “ 

Cast-iron  “ “ 2,780°  “ 

Steel  “ “ 4,000°  ‘‘ 


Wrought-iron  “ above 4,000°  “ 

* Estimates  of  temperature  above  the  fusing-point  of  zinc  caimot  be 
regarded  as  exact,  on  account  of  the  difficulty  of  ascertaining  them. 


10 


NAVAL  ORDNANCE  AND  GUNNERY. 


35.  Hot-blast. — When  tlie  stream  of  air  forced  tlirougli  a 
furnace  is  heated  above  300°  or  400°  F.,  it  is  called  a hot-blast. 

36.  Effects  of  IIotMast. — Whenever  a forced  stream  of  air 
is  employed  for  combustion,  the  resulting  temperature  must 
evidently  be  impaired  by  the  coldness  of  the  air  injected  upon 
the  fuel ; fires  fed  with  hot  air  should,  with  the  same  fuel,  rise 
to  a higher  temperature  than  fire  fed  with  common  cold  air. 

Furnaces  blown  with  heated  air  exert  greater  reductive 
power  than  those  in  which  a cold-blast  is  used.  This  has  led, 
since  tlie  introduction  of  hot-blast,  to  the  extensive  use  in  iron- 
smelting of  refractory  ores  not  formerly  smelted ; a large 
part  of  which  have  been  ores  of  a class  calculated  to  produce 
inferior  iron ; and  it  is  to  the  use  of  ores  of  this  nature,  far 
more  than  from  any  detei’ioration  in  quality,  arising  from  a 
heated  blast,  that  the  frequent  inferiority  of  hot-blast  iron  is 
to  be  ascribed. 

As  the  fusing  metal  is  brought  in  contact  with  less  fuel, 
and  as  less  air  is  passed  through  the  furnace,  the  chemical  reac- 
tions are  probably  somewhat  modified,  hut  it  is  thought  the 
quality  of  the  product  is  not  injured. 

37.  Excessive  Heat  of  Eurnace. — An  excessive  temperature 
in  the  furnace  is  injurious,  because  unnecessary  heat  of  fusion 
injures  the  quality  of  the  metal  produced  ; dark-gray  graphitic 
iron  resulting  always  from  intensity  of  heat. 

But  this  can  be  regulated  as  well  with  the  hot-blast  as  with 
the  cold  : since  it  depends  on  the  fuel  employed,  the  burden  of 
ore,  and  the  pressure  of  the  blast,  as  Avell  as  its  temperature. 

38.  Advantages  of  Hot-blast. — With  fuels  difiicult  of 
ignition,  and  with  refractory  ores,  the  advantages  of  the  hot- 
blast  are  most  marked.  It  effects  a saving  of  heat,  and  accom- 
plishes the  reduction  of  the  most  refractory  ores  in  less  time 
and  with  a less  expenditure  of  fuel  than  the  cold-blast. 

It  is  therefore  employed  at  the  present  day  almost  to  the 
exclusion  of  cold-blast,  the  latter  being  retained  only  for  cer- 
tain special  makes,  such  as  for  gun-founding,  which  command 
an  extra  price,  and  may  therefore  be  produced  without  strict 
regard  to  economy. 

39.  AYakm-blast. — Even  for  purposes  where  it  is  desirable 
to  produce  the  best  possible  quality  of  iron  without  regard  to 
cost  it  is  now  customary  to  use  a warm-hlast  rather  than  the 
cold ; that  is  to  say,  a blast  varying  from  100°  to  200°  F.,  so  as 
to  obtain  uniformity  of  temperature  at  all  seasons  of  the  year ; 
which  is  not  possible  when  using  a blast  absolutely  cold. 

40.  Some  of  the  latest  experiments  upon  the  comparative 
strengths  of  hot-blast  and  cold-blast  irons  appear  to  warrant  the 


CANNON  IIETALS. 


11 


conclusion,  that  so  far  as  the  temperature  of  the  blast  only  is 
concerned,  the  hot-blast  tends  slightly  to  injure  the  quality  of 
the  softer  (gray)  irons,  wliilst  it  improves,  sometimes  in  a very 
remarkable  degree,  the  character  of  the  harder  (white)  cast- 
irons. 

41.  Method  of  Heating  the  Blast. — The  combustible 
gases  from  the  stack  are  generally  used  to  heat  the  air.  For 
this  purpose  a kind  of  oven  is  built  near  the  stack,  and  the 
inflammable  gases  are  drawn  off  from  the  top  and  passed 
through  it.  In  this  oven  are  series  of  pipes  through  which  the 
air  is  forced  before  it  enters  the  stack ; sometimes  this  oven  is 
heated  independently  of  the  stack. 

42.  The  amount  to  which  the  temperature  of  the  blast  may 
be  raised  with  advantage  does  not  appear  to  have  any  practical 
limit,  except  that  arising  from  the  necessity  of  keeping  the 
apparatus  tiglit,  and  avoiding  its  rapid  destruction  by  excessive 
heat.  Yet,  Bell  says  1,000°  F.  should  be  the  limit  even  in  the 
largest  furnaces.  (Art.  45.) 

43.  Blowing  in  is  the  operation  of  starting  the  furnace. 

In  manufacturiug  gun-iron  charcoal  is  used  with  limestone 
as  a flux. 

To  commence  blowing  in,  first  put  a quantity  of  good  dry 
v/ood  in  the  bottom,  raising  it  to  a height  of  three  or  four  feet, 
and  then  several  tons  of  charcoal ; over  this  are  introduced  regu- 
lar layers  of  charcoal,  flux,  and  a very  light  burden  of  ore. 
AVhen  the  furnace  is  thus  filled,  to  about  one-third  its  lieight, 
the  wood  at  the  bottom  is  ignited.  When  the  upper  layers  be- 
come incandescent  the  charging  is  resumed  until  the  furnace  is 
two-thirds  lull,  the  burden  of  ore  being  gradually  increased,  up 
to  that  necessaiy  for  producing  gray  iron  of  the  proper  quality 
in  the  ordinary  working.  AVhen  the  Are  reaches  the  top  of  the 
minerals  the  furnace  is  filled  up  to  the  top,  and  the  blast  turned 
on  to  about  two-thirds  its  full  force. 

This  continues  for  a time,  when  the  blast  is  turned  full  on, 
and  the  chavging  goes  on  regularly. 

The  weight  of  the  charges  as  well  as  the  temperature  and 
pressure  of  blast  must  be  gradually  increased  so  as  to  get  to  the 
proper  burden  by  degrees. 

44.  AVoeking  of  the  Fuenace. — When  the  furnace  is  at 
work  or  in  blast  it  is  kept  filled  to  the  top  or  throat,  with  alter- 
nate layers  of  fuel,  ore  and  flux,  the  latter  being  mixed  in 
proper  proportions,  to  produce  the  most  fusible  combination  of 
the  earthj^  matters ; a constant  stream  of  air  being  maintained 
through  the  twyers,  at  a sufficient  pressure  to  pass  freely 
through  the  contents  of  the  furnace. 


12 


NAVAL  ORDNANCE  AND  GDNNEET. 


45.  Chemical  Action  in  the  Furnace.^ — The  oxygen  of 
the  blast  coming  in  contact  with  a great  excess  of  incandescent 
fuel  is  saturated,  so  to  speak,  at  once  with  carbon,  and  carbonic 
oxide  is  formed.  The  heat  thus  generated,  though  not  the 
maximum  which  the  fuel  would  produce  if  burnt  with  excess 
of  air,  suffices  to  fuse  the  carburetted  iron,  and  the  silicious 
compounds  descending  from  above ; and  they  fall  into  the 
hearth  when  they  separate  by  liquation  into  metal  and  slag. 
The  latter,  being  specifically  lighter,  rises  to  the  surface,  and 
protects  the  former  from  the  decarbonizing  action  of  the  blast. 

The  carbonic  oxide  produced,  together  -with  the  inert  nitro- 
gen, rises  through  the  incandescent  materials  of  the  furnace 
and  at  a certain  Tieight,  within  ten  or  fiften  feet  of  the  top  -of  a 
fifty  or  sixty-five  feet  stack,  where  the  temperature  is  compara- 
tively low  (probably  not  exceeding  the  melting-point  of  zinc), 
the  reduction  of  the  oxide  of  iron  takes  place.  The  reaction 
may  be  approximately  expressed  thus: — Fe^Oj -j- SCO  = 2Fe 
+ SCO,. 

The  CO,  formed  reacts  immediately  on  the  hot  coal,  and  is 
converted  again  to  CO,  and  this  reduces  more  ii’on  oxide,  and 
thus  the  interaction  continues  until  certain  proportions  of  CO 
and  CO,  obtain,  wlien  the  reducing  action  of  CO  becomes  less 
powerful  than  the  tendency  of  CO,  to  oxydize  the  newly 
formed  metal. 

The  power  of  CO,  to  oxydize  iron  over  that  of  CO  to 
reduce  it  increases  with  the  temperature.  At  a liigh  heat,  too, 
an  excess  of  CO  is  produced,  as  carbon  reduces  CO,  better  at 
high  temperatures. 

These  facts,  according  to  Bell,  set  a limit  to  the  degree  of 
heat  at  which  the  blast  can  be  advantageously  used. 

The  escaping  gases  scarcely  ever  contain  more  than  forty 
parts  of  CO,  to  one  hundred  CO  by  volume,  and  this  is  diluted 
with  about  two  hundred  parts  of  nitrogen. 

It  follows  that  only  one-fifth  of  tbe  carbon  is  wholly  con- 
sumed in  the  blast-furnace. 

Another  important  reaction  takes  place  below  the  reducing- 
zone,  depending  on  the  fact  that  carbonic  oxide  is  itself  reduced 
with  the  elimination  of  carbon,  or  decomposed  according  to  the 
formula  2CO  = C -|-  CO,  in  the  presence  of  metallic  iron,  and 
the  lower  oxides  of  iron  at  a certain  temperature  somewhat 
higher  than  that  most  favorable  for  the  reduction  of  the  iron 
oxide. 

The  spongy  metallic  iron,  probably  not  wholly  reduced, 

* Bell’s  Chemical  Phenomenon  of  Iron-smelting. 


CANNON  METALS. 


13 


descends  nnmelted  into  the  bottom  portions  of  the  furnace 
where  the  reduction  is  perfected,  probably  by  the  finely  divided 
carbon  resulting  from  the  reaction  described  above.  At  the 
zone  of  fusion,  just  above  the  twyers,  the  iron  combining  wfitli 
a portion  of  this  carbon,  and  with  varying  quantities  of  silicon, 
etc.,  melts  and  falls  into  the  hearth  below  as  cast-iron. 

46.  Production  of  Gun-iron. — It  is  very  necessary  that 
this  should  be  of  uniform  strength  and  density.  In  order  to 
produce  the  best  quality  of  iron  the  greatest  care  is  required. 

All  the  materials  which  enter  the  furnace  should  be  of  the 
best  and  purest  quality,  and  kept  dry ; regularly  and  uniformly 
mixed,  and  supplied  to  the  furnace  at  regular  intervals. 

The  temperature  of  the  blast  should  be  kept  as  nearly  uni- 
form as  possible,  without  using  what  is  termed  the  hot-hlast, 
which  is  on  no  account  to  be  used. 

47.  Tapping. — The  molten  metal  accumulating  in  the 
hearth  of  the  furnace  is  removed  at  regular  intervals  by  tap- 
ping, or  piercing  a hole  through  the  lower  part  of  the  dam,  and 
allowing  the  metal  to  flow  into  sand  or  cast-iron  moulds  placed 
in  front  of  the  furnace. 

Before  tapping,  the  blast  is  shut  off  and  the  tymp-stopping 
removed. 

The  tap-hole  is  opened  by  driving  in  the  point  of  a wrought- 
iron  bar,  which  is  held  by  one  man  while  another  strikes  the 
end  with  a sledge-hammer  if  necessary. 

48.  The  molds,  or  pig-beds,  usually  consist  of  a series  of 
furrows  in  the  sand  of  the  casting-floor,  molded  by  a wooden 
core  having  the  name  or  mark  of  the  foundry  attached  to  it. 

The  molds  are  arranged  in  parallel  series  on  either  side  of 
a central  feeder,  known  as  a sow  y and  as  soon  as  one  series  is 
tilled  the  current  is  allowed  to  flow  into  the  next,  and  so  on, 
until  the  cast  is  completed.  For  gun-iron  sand-molds  should 
be  used. 

When  this  operation  ceases  the  tap-hole  is  again  secured, 
and  the  work  proceeds  as  before.  In  this  manner  a furnace 
may  be  kept  continually  going  night  and  day  for  years,  until 
rejiairs  render  Mowing  out  neeessar}. 

49.  Piling  Pigs. — Each  pig  of  any  one  run  should  be  placed 
in  a separate  pile,  aiid  each  of  these  piles  should  be  kept  sepa- 
rate in  transportation,  and  be  re-piled  in  the  foundry  yard  in 
the  same  order  as  at  the  smelting-furnace. 

These  precautions  are  necessary  in  order  to  have  an  accurate 
history  of  the  metal  of  which  each  gun  is  made. 


14 


NAVAL  ORDNANCE  AND  GUNNERY. 


Section  II. — Cast-Iron. 

50.  Composition  of  Cast-Ikon.'^ — The  only  substance  with 
which  iron  is  invariably  and  indispensably  associated  in  cast- 
iron  is  carbon.  By  fusing  finely  divided  iron  with  charcoal 
until  the  metal  has  taken  up  as  much  carbon  as  it  will  dissolve, 
a dark-gray  mass  is  obtained,  which  is  so  brittle  that  it  may  be 
powdered  in  a mortar. 

That  carbon  forms  any  definite  compound  with  iron  is  very 
doubtful. 

Iron  seems  to  have  the  power  of  dissolving  carbon  at  a high 
temperature,  and  on  slow  cooling  the  carbon  is  separated  in  dis- 
tinct graphitic  scales.  If  the  cooling  is  very  slow  large  crystals 
one-half  to  three-fourths  of  an  inch  long  are  formed,  and 
graphite  may  be  readily  removed  from  the  faces  with  a knife. 
On  chilling  gray  iron  the  carbon  is  retained  in  a more  intimate 
state  of  combination  or  solution,  and  cannot  be  separated. 

As  to  whether  the  carbon  is  chemically  combined,  or 
whether  it  is  carbon  in  another  form  than  graphite  simply  dis- 
solved in  the  iron,  difierent  opinions  exist. 

The  percentage  of  carbon  in  the  best  varieties  of  pig-iron 
varies  from  three  to  rather  over  four  per  cent.,  except,  perhaps, 
in  the  variety  of  iron  known  as  sj>iegeleisen,  which  sometimes 
contains  nearly  five  per  cent. 

51.  YAPaETiES  OF  Cast-Ikon. — On  examining  the  fractures 
of  freshly  broken  pieces  of  cast-iron,  it  will  be  found  that  some 
specimens  have  a silvery-white  and  others  a gray  color,  caused 
by  the  presence  of  very  minute  particles  of  carbon,  which  are 
interspersed  among  the  lighter-colored  particles  of  the  metal. 

When  the  gray  samples  of  cast-iron  are  acted  upon  by  acid 
(diluted  sulphuric  or  hydrochloric)  the  iron  is  dissolved,  but  the 
black  particles  of  carbon  are  left,  and  these  are  found  to  possess 
the  same  propeidics  as  the  natural  variety  of  carbon,  known  as 
black-lead,  or  graphite,  of  which  pencils  are  made. 

When  the  white  cast-iron  is  dissolved  in  acids  very  little 
black  residue  of  carbon  is  left,  because  the  greater  part  of  the 
carbon,  being  intimately  combined  with  the  iron,  is  dissolved 
by  the  acid,  or  eliminated  as  gaseous  hydro-carbons,  and  very 
little  is  presented  in  the  form  of  graphite. 

52.  When  a sample  of  gray  cast-iron  is  melted,  the  particles 
of  the  free  carbon  are  dissolved  by  the  liquid  metal  becoming 
intimately  combined  with  the  iron  ; and  if  the  melted  mass  be 


Bloxam. 


CANICON  METALS. 


15 


suddenly  cliilled  by  throwing  water  npon  it,  or  by  running  it 
when  near  its  point  of  solidification  into  a thidv  iron  mould, 
the  carbon  does  not  separate  again,  so  that  a mass  of  white  cast- 
iron  is  thus  produced. 

63.  It  is  more  difficult  to  convert  the  white  into  the  gray 
variety  of  cast-iron,  but  this  can  be  done  by  exposing  the  melted 
metal  to  a high  temperature,  and  allowing  it  to  cool  down  very 
slowly,  when  a portion  of  the  carbon  separates  from  the  iron, 
and  the  gray  variety  of  cast-iron  is  produced. 

The  relative  grayness  or  whiteness  of  pig-iron  furnishes  no 
real  standard  of  quality  as  compared  with  the  produce  of  other 
localities,  but  is  rather  an  indication  of  the  wmrking  condition 
of  the  furnace. 

51.  The  variable  qualities  of  ore,  fuel,  and  limestone  may 
exercise  such  an  influence  on  the  resulting  crude  iron  as  to  ren- 
der a lofv  denomination  of  one  manufacbire  of  greater  commer- 
cial value  than  a higher  denomination  of  other  makes.  Other 
things  being  equal  white  cast-iron  can  be  more  readily  and 
cheaply  produced  than  gray,  as  the  same  amoiint  of  fuel  is  made 
to  carry  a larger  burden  of  ore,  and  the  charges  are  driven  more 
rapidly.  As,  however,  it  can  only  l)e  used  for  forge  purposes, 
while  the  more  expensive  gray  metal  is  available  for  making 
castings  or  malleable  iron,  it  is  usually  sought  to  diminish  its 
production  as  much  as  possible,  except  in  special  cases,  Avhere 
quantity  of  make  or  an  extreme  economy  of  fuel  is  desired. 

55.  Gray  Cast-iron. — Since  in  gray  cast-iron  a smaller  pro- 
portion of  the  iron  is  in  combination  with  carbon,  and  more  of 
it  in  the  true  metallic  state,  this  variety  would  be  expected  to 
exhibit  more  of  the  properties  of  metallic  iron.  Accordingly 
the  gray  cast-iron  is  much  softer  and  less  brittle  than  white 
iron  ; it  is  in  a slight  degree  malleable  and  flexible.  The  larger 
proportion  of  metallic  iron  contained  in  the  gray  cast-iron  causes 
it  to  require  a higher  degree  of  heat  before  it  begins  to  show 
signs  of  fusion,  but  it  is  capable  of  becoming  very  liquid  at  a 
sufficiently  high  temperature,  so  as  to  be  easily  run  into  molds. 
It  becomes  more  fluid  and  preserves  its  fluidity  longer  than 
white  iron ; it  expands  on  becoming  solid  so  as  to  be  capable  of 
Ailing  up  the  smallest  cavities  and  depressions  of  a mold. 

Gray  cast-iron  is  about  one-twentieth  lighter  than  the  white 
variety  ; its  average  speciflc  gravity  is  7.1.  The  gray  iron 
rusts  more  easily  in  air  and  is  more  readily  acted  upon  Avith 
acids  than  Avhite  iron,  Avhich  may  be  ascribed  partly  to  its 
containing  more  iron  in  an  uncombined  form,  and  partly  to  the 
acceleration  of  chemical  action  caused  by  the  voltaic  disturbance 
excited  by  the  contact  of  the  particles  of  graphite  Avith  the  par- 


IG 


NAVAL  ORDNANCE  AND  GUNNERY. 


tides  of  iron  in  the  presence  of  the  acid ; in  the  ease  of  air,  car- 
bonic acid.  This  variety  of  iron  is  used  for  ordnance  purposes 

56.  White  Cast-ieon. — Since  in  white  cast-iron  a considera- 
ble proportion  of  the  iron  is  in  intimate  combination  with  car- 
bon, this  variety  would  be  expected  to  present  the  characters  of 
the  compound  of  carbon  with  iron,  described  above  (Art.  50j ; 
accordingly  the  white  cast-iron  is  very  brittle  and  extremely 
hard,  so  that  a lile  will  scarcely  tonch  it,  whereas  gray  iron  is 
much  softer,  and  admits  of  being  filed  and  turned. 

White  cast-iron  is  softened  at  a lower  temperature  than  gray, 
but  becomes  less  perfectly  fluid ; in  cooling  it  passes  through 
the  pasty  or  semi-fluid  state,  and  contracts  very  considerably  on 
solidification.  It  scintillates  or  throws  off  sparks,  as  it  runs 
from  the  furnace,  to  a much  greater  extent  than  gray  iron. 

Its  average  specific  gravity  is  7.5. 

White  iron  usually,  but  by  no  means  invariably,  contains 
less  total  carbon  than  gray  iron.  Its  qualities  generally  are  the 
reverse  of  those  of  gray  iron,  and  it  is  therefore  unsuitable  for 
ordnance  purposes. 

57.  There  are  two  distinct  kinds  of  white  iron.  First,  That 
obtained  from  ores  containing  a larger  proportion  of  manganese 
crystallizing  in  large  plates;  this  variety,  called  spiegeleisen,  is 
highly  prized  for  making  steel ; and  Second,  Tliat  resulting 
from  a heavy  mineral  burden  of  the  furnace,  or  from  a general 
derangement  of  its  working,  and  that  caused  from  the  rapid 
chilling  of  fused  gray  iron. 

58.  Mottled  Cast-ieox  is  composed  of  a mixture  of  the 
■white  and  the  gray  varieties  in  varying  proportions,  the  gray 
iron  sometimes  appearing  in  specks,  like  minute  flowers  upon  a 
white  ground,  whilst  in  other  specimens  the  mass  is  composed 
of  gray  iron  and  the  white  iron  appears  in  spots.  Fine  gray 
mottled  iron  from  its  great  tenacity  is  known  to  be  the  best 
fitted  for  large  castings  where  great  strength  is  required,  and  is 
employed  for  gun-founding.  It  may  be  made  by  mixing  white 
and  gray  iron,  or  by  continuing  gray  iron  in  fusion  for  some 
time,  until  it  gets  the  proper  color.  The  kind  of  mottle  will 
depend  much  upon  the  size  of  the  castings.  (Art.  364.) 

59.  Classification  of  Pig-ieon. — Generally  a medium-sized 
gram,  light-gray  color,  lively  aspect,  fracture  sliaiq)  to  the  touch, 
and  a close,  compact  texture  indicate  a good  quality  of  iron; 
while  a grain  either  very  large  or  very  small,  a dull  earthy 
aspect,  loose  texture,  dissimilar  crystals  mixed  together  indicate 
an  inferior  quality. 

The  produce  of  the  blast-furnace  is  di-visible  into  several 
qualities,  which  for  practical  purposes  are  determined  by  the 


CANXON  EIETALS. 


17 


appearance  presented  by  a freshly  fractured  surface — a num- 
ber of  pigs  taken  from  each  cast  being  broken  for  the  purpose. 

The  numerous  gradations  in  the  scale  are  mainly  dependent 
on  color  or  degree  of  grayness,  texture  or  size  of  crystals,  and 
their  uniformity  and  lustre.  The  largest-grahmd,  brilliant,  and 
graphitic  dark-gray  metal  is  known  as  hfo.  1 pig,  while  the 
smaller-grained  varieties,  with  diminishing  lustre  and  color,  are 
designated  by  the  higher  numbers  as  far  as  ISlo.  4. 

IBeyond  this  point,  when  the  metal  ceases  to  be  gray,  it  is 
usual  to  omit  the  numerical  scale,  and  denominate  the  remain- 
ing qualities  by  their  color,  as  mottled^  weak  and  strong  mottled, 
and  white,  the  last  being  the  lowest. 

This  classification  is  subjected  to  variations  in  different  locali- 
ties. 

The  gray  numbers  as  far  as  ISTo.  3,  are  also  called  melting  or 
foundry -pigs  / the  lower  qualities,  wTieh  are  only  adapted  for 
conversion  into  malleable  iron,  coming  into  the  class  of  forge- 
pigs. 

60.  Yakiatioxs  in  Composition  of  Cast-ieon. — Although 
carbon  appears  to  be  the  only  substance  mdispensably  associated 
with  the  metal  in  cast-iron,  the  commercial  varieties  of  this 
material  always  contain  silicon,  phosphorus,  sidphur,  and 
manganese,  v’hich  are  often  present  in  considerable  proportion, 
and  are  known  to  exercise  an  influence  upon  the  character  ol; 
the  cast-iron ; other  substances,  such  as  titanium,  cobalt,  nickel, 
chromium,  copper,  vanadium,  calcium,  magnesium  and  arsenic 
may  also  be  discovered  by  a careful  analysis  of  considerable 
quantities  of  cast-iron,  but  they  are  generally  present  in  very 
small  proportion,  and  are,  not  known  to  produce  any  effect  on 
the  metal. 

The  following  table  illustrates  the  general  composition  of 
the  three  principal  varieties  of  cast-iron  : 


Gray. 

Mottled. 

WMte. 

Iron 

. . 90.24 

89.31 

89.86 

Combined  carbon . . . 

. . 1.02 

1.79 

2.46 

Graphite 

. . 2.64 

1.11 

0.87 

Silicon 

. . 3.06 

2.17 

1.12 

Sulphur 

. . 1.14 

1.48 

2.52 

Phosphorus 

. . 0.93 

1.17 

0.91 

Manganese 

. . 0.83 

1.60 

2.72 

99.86  93.63  100.46 


61.  The  difiicillties  attending  the  chemical  analysis  of  cast- 
2 


18 


NAVAL  OEDNANCE  AND  GDNNERT. 


iron  are  very  great  on  account  of  the  large  quantity  of  iron 
which  has  to  he  separated  from  small  quantities  of  the  other 
constituents,  so  that,  although  numerous  analyses  are  recorded, 
their  results  do  not  exhibit  that  agreement  which  is  necessary 
in  order  that  the  composition  of  this  material  may  be  considered 
to  be  thoroughly  established. 

There  appears  to  be  little  knowledge  of  a thoroughly  satis- 
factory character  with  respect  to  the  eifect  of  different  propor- 
tions of  foreign  matter  upon  the  quality  of  iron,  for  the  exact 
analysis  of  this  material  is  tedious  and  difficult ; and  those  who 
are  competent  to  execute  it  in  a trustworthy  manner  have 
rarely  the  opportunity  of  becoming  practically  acqiiainted  with 
the  behavior  of  the  metal. 

62.  Silicon. — 1ST ext  to  carbon  silicon,  or  silicum,  is  the  com- 
monest and  most  abundant  constituent  of  cast-iron  ; its  effect  is 
very  similar  to  that  of  carbon,  and  its  tendency  is  to  reduce  the 
percentage  of  carbon.  It  is  an  element  that  is  always  present 
in  every  form  of  iron,  although  at  times  its  quantity  is  very 
minute  ; the  proportion  of  silicon  being  higher  in  the  gray  than 
in  the  white  variety,  and  the  greater  the  quantity  of  graphite 
in  the  crude  iron,  the  larger  the  amount  of  silicon. 

The  best  common  iron  contains  from  one  to  one  and  one- 
fourlli  per  cent,  of  silicon.  Such  iron  has  a smoother  face  than 
inferior  pig,  and  when  struck  with  a hammer  rings  ; it  is  brit- 
tle and  crystalline  ; whereas  inferior  pig  contains  only  two  to 
four-tenths  of  silicon,  is  rough  on  the  face  or  surface,  breaks 
with  less  ease  than  the  crystalline  pig,  and  when  struck  sounds 
dead  like  lead,  without  ringing  at  all. 

Silicon  exists  in  cast-iron  sometimes  combined  and  some- 
times separate,  and  is  derived  from  silica  in  the  ore  or  in  the 
fuel ; silica  is  a combination  of  silicon  with  oxygen,  and  when 
the  latter  is  abstracted  by  the  carbon  at  the  high  temperature 
of  the  blast-furnace,  the  silicon  enters  into  combination  with  the 
iron. 

The  presence  of  a large  proportion  of  silicon  in  cast-iron  is 
generally  considered  injurious  to  its  quality,  the  strongest  cast- 
irons  being  those  which  contain  a small  quantity  of  that  ele- 
ment. 

Iron  which  has  been  smelted  with  coke  contains  a larger 
proportion  of  silicon  than  that  smelted  with  charcoal,  and  hot- 
blast  iron  commonly  contains  more  than  that  smelted  by  cold- 
blast. 

The  presence  of  silicon  in  pig-iron  affects  in  a remarkable 
degree  the  yield  as  well  as  the  strength  of  the  bar-iron  produced 
therefrom.  It  is  necessary  that  this  element  should  be  removed 


CANlSrOIT  METALS. 


19 


as  inncli  as  possible  bv  a refining  process,  before  the  crude  iron 
is  submitted  to  the  puddling  process ; but  as  this  involves  a 
great  waste  of  material  and  trouble,  it  becomes  an  object  of 
much  practical  importance  to  prevent,  as  far  as  possible,  the 
presence  of  this  element  in  the  crude  iron. 

In  refining  iron  the  silicon  is  oxydized  before  the  carbon, 
and  in  some  cases  the  silicon  is  separated  completely  from  the 
metal,  existing  only  as  traces.  The  time  required  to  refine  iron 
seems  to  depend  upon  the  amount  of  silicon  present  in  the  pig ; 
thus,  gray  iron  requires  much  longer  time  than  white,  and  when 
very  silicious  white  iron  or  glazed  gray  pig  is  used,  it  is  almost 
impossible  to  refine  it. 

It  has  always  been  the  general  impression  that  any  amount 
of  silicon  in  steel  reduces  its  quality  and  seriously  impairs  its 
strength ; good  steel  may,  however,  contain  two  per  cent,  of  sili- 
con, and  its  presence  makes  steel  castings  more  solid.* 

63.  Maxoaxksu  is  seldom  if  ever  absent  from  cast-iron,  for 
it  is  a metal  which  very  nearly  resembles  iron  in  its  chemical 
properties,  and  is  commonlj^  found  in  iron  ores,  so  that  the  same 
operation  which  reduces  the  iron  in  the  blast-furnace  also  reduces 
the  manganese,  and  this  metal  becomes  alloyed  or  closely  mixed 
with  the  melted  iron. 

The  manganese  has  been  found  in  the  large  proportion  of 
one-sixteenth  of  the  weight  of  the  cast-iron,  but  it  seldom  ex- 
ceeds one-fortieth. 

The  influence  exerted  by  the  manganese  upon  the  character 
of  the  cast-iron  is  very  decided,  tending  to  the  production  of  the 
white  variety,  the  manganese  diminishing  the  tendency  of  the 
carbon  to  separate  in  the  form  of  graphite. 

AVhite  east-iron,  therefore,  is  found  to  contain  the  largest 
proportion  of  manganese. 

The  spathic  iron  ores  yield  a cast-iron  containing  a particu- 
larly large  quantity  of  manganese,  sometimes  exceeding  one-tenth 
of  the  weight  of  the  cast-iron.  Such  an  iron  is  capable  of  con- 
taining upwards  of  one  twenty-fifth  of  its  weight  of  carbon  in 
combination  with  it,  and  the  compound  thus  formed  ciy stall izes 
in  large  and  shining  plates,  whence  it  is  named  by  the  Germans 
sjyiegeleisen,  or  mirror-iron.  It  is  largely  employed  in  the  man- 
ufacture of  Bessemer  steel. 

It  has  been  asserted  that  the  presence  of  manganese  in  iron 
ores  encourages  the  passage  of  phosphorus,  sulphur,  and  silicon 
into  the  slag,  thus  reducing  the  proportion  of  those  injurious 
impurities  in  the  metal. 


Eilej. 


20 


NAVAL  ORDNANCE  AND  GUNNERY, 


04.  PiiospnoEUS  is  one  of  the  most  unwelcome  ingredients 
in  iron  ores,  from  tlie  ease  with  which  it  passes  into  the  metal 
during  the  smelting  process,  producing  the  most  injurious 
effects,  if  present  in  more  tlian  a very  small  proportion. 

Practically  speaking,  all  the  phosphorus  in  the  ore  and  in 
the  fuel  passes  into  the  pig-iron  made  ; like  silicon  it  makes  pig- 
iron  weak,  although  it  is  thought  that  when  the  amount  is  not 
more  than  one-half  to  three-fourths  per  cent.,  the  strength  of  the 
pig-iron  is  not  materially  affected  by  it. 

Phosphorns  occasionally  forms  between  one-fiftieth  and  one- 
sixtieth  part  of  the  weight  of  cast-iron,  but  about  one-hundredth 
part  is  a more  common  proportion  of  phosphorus.  It  exists  in 
combination  with  a portion  of  the  metal  as  j>hospMde  of  iron, 
and  is  derived  either  from  phosphate  of  iron  contained  in  the 
ore,  or  from  phosphate  of  lime,  which  is  frequently  present  in 
the  limestone  employed  as  a flux,  and  in  minute  quantity  in  the 
coal.  These  phosphates  contain  phosphorus  in  a state  of  com- 
bination with  oxygen,  which  is  abstracted  by  the  carbon  of  the 
fuel  in  the  blast-furnace,  and  the  phosphorus  thus  set  free  enters 
into  combination  witli  the  iron.  So  completely  is  the  phos- 
phorus taken  up  by  the  metal,  that  only  traces  of  that  element 
in  the  form  of  phosphates  are  usually  found  in  the  slag  from 
the  blast-furnace. 

The  effects  of  phosphorus  are  to  harden  cast-iron,  decrease 
its  strength,  and  increase  its  fusibility.  Iron  made  from  ores 
containing  much  phosphorus  is  always  cold-short,  or  incapable 
of  being  wrought  cold  under  the  hammer  without  breaking. 

G5.  SuLPiiiJE,  though  almost  invariably  contained  in  cast- 
iron,  rarely  forms  as  much  as  OTie-fiftieth  of  its  weight.  It  is 
chiefly  derived  from  ironpyrites,  which  is  the  yellow  substance, 
of  metallic  appearance,  so  common  in  lumps  of  coal,  and  may 
be  found  in  rusty  globular  masses  on  the  sea-beach. 

It  is  composed  of  iron  combined  with  sulphur  in  nearly  equal 
proportions,  and  since  crystals  of  ironpy rites  are  found  in  many 
iron  ores,  it  is  the  chief  source  of  the  sulphur,  which  is  the  most 
objectionable  impurity  in  iron. 

The  most  prejudicial  form  in  Avhich  sulphur  can  exist  in  the 
blast-furnace  is  when  it  occurs  as  sulphide  of  iron ; it  has  no 
prejudicial  effect  when  it  exists  as  sulphide  of  calcium. 

Large  quantities  of  sulphur  may  be  present  as  a sulphate  of 
an  alkaline  earth  without  having  any  effect  on  the  quahty  of 
the  iron  produced. 

The  white  varieties  of  cast-iron  contain  a larger  proportion 
of  sulphur  than  the  gray,  and  it  will  make  gray  non  white.  It 
is  thought  that  slightly  different  amounts  of  it  may  modify  the 


CAis^NON  METALS. 


21 


pig-iron,  and  produce  tlie  difference  we  find  in  it,  for  practically 
there  is  a very  great  difference  in  the  Avorking  of  the  different 
grades  of  iron,  Avhen  chemically  speaking  there  may  be  no  dif- 
ference apparent. 

Tlie  percentage  of  sulphur  usually  increases  as  the  quality 
of  the  pig  decreases,  and  its  presence  tends  to  red-shortness  in 
bar-iron,  rendering  it  incapable  of  being  worked  at  a red  heat 
under  the  hammer.  This  element  also  imparts  to  crude  iron 
the  property  of  becoming  viscid  and  of  solidifying  c^uickly  with 
cavities  and  air-bubbles. 

Iron  may  be  both  red-short  and  cold-short  at  the  same  time. 
Such  iron  is  the  worst  possible  iron,  and  is  made  from  ores  con- 
taining a high  percentage  of  sulphur  and  phosphorus. 


Section  III.—  WrougJit-lron. 

66.  "WnouGnT  ok  Malleable  Ikon.* — This  is  the  nearest 
approach  to  the  chemically  pure  metal  that  can  be  obtained  on 
the  large  scale,  and  may  be  almost  absolutely  free  from  carbon. 
It  never  contains  more  than  one-fourth  per  cent. 

67.  It  is  a soft,  malleable,  and  extremely  tenacious  substance, 
infusible  except  at  extreme  temperatures  obtainable  in  furnaces 
of  special  construction,  but  capable  of  being  agglomerated  by 
pressure,  when  at  a white  heat,  to  a compact  state  by  the  pro- 
cess of  Avelding. 

68.  IIoAV  Peoduced. — It  may  be  produced  either  directly 
from  the  ore,  or  by  the  conversion  of  pig-iron. 

Varieties. — TheA’arietiesof  malleable  iron  are  distinguished 
by  many  different  names,  but  they  have  reference  rather  to  form 
and  destination  than  to  difference  of  composition. 

69.  CoNVEESiox  OF  Ckude  INTO  Malleable  Ieon. — This  is 
effected  by  one  or  more  operations,  which  are  necessarily  of  an 
oxydizing  nature,  the  object  being  to  eliminate  from  the  cast- 
iron  the  carbon  in  the  form  of  carbonic  oxide  gas,  and  the  sili- 
con, sulphur,  phosphorus,  and  other  foreign  bodies  in  the  form 
of  oxydized  products  which  pass  either  partially  or  wholly  into 
slag  or  cinders. 

70.  T aeiotjS  Peocesses. — The  numerous  processes  em- 
ployed in  the  production  of  malleable  from  cast-iron  are  divisi- 
ble into  two  classes,  according  to  the  nature  of  the  furnaces 
employed. 

First.  The  ogpen-jire.^  or  hearth-furnaces,  where  the  pig-iron 


* Bauerman. 


22 


NAVAL  ORDNANCE  AND  GUNNERY. 


is  melted  and  decarbonized  in  a shallow  hearth  before  the  blast 
of  an  inclined  twyei’. 

Secondly.  The  yyxoddling-furnaces,  where  the  same  operation 
is  performed  on  the  bed  of  a reverberatory  fm-nace. 

71.  Chemical  Reactions. — The  reactions  going  on  during 
the  process  are  similar  in  either  case. 

The  carbon,  if  it  exist  originally  as  graphite,  first  passes  into 
the  combined  state,  and  is  then  converted  into  carbonic  oxide 
either  by  the  oxygen  of  the  blast  dmectly,  or  indh’eetly  by  the 
oxide  of  iron  dissolved  in  the  slag. 

Oxydizing  agents  for  the  indirect  conversion  may  be  derived 
from  the  pig-iron  under  treatment,  which  is  always  oxydized 
to  a certain  extent  under  the  influence  of  the  blast  cluiing  the 
melting,  or  they  may  be  added  in  the  form  of  ore,  forge-scales, 
or  slags. 

According  to  the  relative  importance  of  the  parts  played  by 
these  agents,  the  process  is  divided  into  dry  and  xcet  puddling, 
the  former  being  dependent  mainly  on  the  exposure  pf  the 
metal  to  the  action  of  the  air,  while  in  the  latter,  which  is  more 
generally  known  as  the  pig-hoiling  process,  the  slag  and  oxide 
of  iron  added  are  the  most  important  oxydizing  agents. 

The  removal  of  the  foreign  matter  in  combination  with  the 
iron  takes  place  in  the  following  order : — ^flrst,  silicon,  then 
manganese,  then  phosphorus,  and  lastly  sulphur,  the  latter  ele- 
ment being  most  difficult  of  removal. 

In  the  treatment  of  gray  pig-iron,  the  graphitic  carbon  is 
transformed  into  the  combined  condition  after  the  removal  of 
the  silicon  during  the  melting  of  the  charge. 

72.  Kind  of  Ikon  most  suitable  for  Conteesion. — White 
cast-iron  is  more  suitable  for  conversion  into  malleable  iron  than 
gray,  as  in  it  the  whole  of  the  carbon  in  combined  with  the  iron, 
and  it  does  not,  when  raised  to  a high  temperatm’e,  pass  imme- 
diately from  the  solid  to  the  liquid  state,  but  assumes,  when  near 
its  melting  point,  an  intermediate  or  pasty  condition  favorable 
to  the  more  effectual  action  of  the  air  or  other  agents  employed 
in  the  removal  of  the  combined  carbon.  Gray  metal,  on  the 
other  hand,  though  recpiiring  a higher  temperature  for  fusion, 
becomes  very  liquid,  and  in  a deep  hearth  sinks  below  the  level 
of  the  blast,  and,  becoming  covered  with  a coating  of  slag,  is 
completely  protected  against  the  action  of  the  air,  unless  it  is 
brought  under  the  influence  of  the  blast  by  stirring  or  hftmg 
with  an  iron  bar,  an  operation  which  involves  great  labor  and  de- 
lay, as  well  as  an  increased  expenditure  of  fuel  and  waste  of  ii’on. 

JSTo  sensible  amount  of  decarburation  takes  place  until  the 
whole  of  the  graphitic  carbon  has  entered  into  combination  with 


CANNON  5IETALS. 


23 


the  iron,  or,  what  amounts  to  the  same  tiling,  until  the  metal  has 
passed  from  the  gray  to  the  white  state  ; and  this  conversion  is 
an  essential  preliminary  in  all  refining  processes  where  the  air  is 
introduced  above  the  surface  of  the  melted  metal. 

73.  Refining. — Gray  pig-ii’on  is  often  subjected,  as  a first 
step  in  the  process  of  making  malleable  iron,  to  a preliminary 
decarburation  in  the  oxydizing  Mast-hearth^  or  rejinery  • this 
process  is  called  refining. 

7d.  The  Puddling  Furnace  is  of  the  reverberatory  form,  one 
in  which  the  flame  is  made  to  pass  over  a bridge  and  then  beat 
down  again  or  reverberate  upon  a hearth  or  surface  on  which 
the  materials  to  be  heated  are  placed. 

It  consists  of  an  oblong  casing  of  iron  plates  (Fig.  G),  firmly 
bound  together  by  iron  tie-bars,  and  lined  with  fire-brick. 

The  fireplace,  F,  is  separated  from  the  hearth,  A,  by  a jire- 
hridge  over  which  the  heated  products  of  combustion  with  a 
surplus  of  oxygen  play  upon  the  sm’face  of  the  molten  metal, 
effecting  its  conversion,  and  thence  pass  through  the  flue  to  a 


Fig.  6. — Puddling  Furnace. 


lofty  chimney,  C,  in  which  is  suspended  a metal  damper-plate, 
by  which  the  draught  can  be  regulated. 

The  Fireplace  varies  in  depth  with  the  nature  of  the  fuel 
employed,  being  greatest  with  the  hard  kinds  of  coal. 


24: 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  fire-grate  is  niade  of  plain  wronght-iron  bars.  A forced 
draught,  produced  by  blowing  air  in  below  the  grate,  is  some- 
tunes  used.  The  surface  of  the  grate  should  be  between  one- 
half  and  one-thh*d  of  that  of  the  bed  or  hearth. 

The  charging  or  fire  hole  is  about  a foot  above  the  grate. 

T/ie  hearth. — The  bottom  of  the  bed  is  formed  of  cast-u’on 
hearth-plates  resting  upon  cast-iron  beams. 

The  hearth  is  covered  with  cinders  or  sand,  and  is  tenni- 
nated  at  either  end  by  a straight  wall  or  bridge,  called  respec- 
tively the  fire-hridge  and  the  jiue-T)ridge. 

The  Flue. — The  roof  of  the  furnace  is  curved  to  a flat  arch, 
and  is  generally  made  to  slope  at  a small  angle  towards  the 
flue,  which  slopes  towards  the  stack. 

The  sectional  area  of  the  flue  varies  with  the  nature  of  the 
fuel,  being  larger  for  soft  coal. 

The  mainworldng-door,  D,  is  made  of  brick  set  in  a cast-iron 
frame ; it  may  be  readily  lifted  and  lowered  by  means  of  a lever. 
It  is  only  opened  during  the  introduction  of  the  charge  and  the 
removal  of  the  puddled  balls.  The  sill  of  the  door  is  about  a foot 
above  the  level  of  the  bed.  There  is  sometimes  a second  work- 
ing-door near  the  flue  for  introducing  the  cast-iron,  so  that  it  may 
soften  slowly  till  it  be  ready  for  drawing  towards  the  bridge. 

The  Stoj)per-hole. — A small  rectangular  or  arched  notch, 
called  the  stopper-hole,  is  cut  out  of  the  lower  edge  of  the  door 
for  the  introdiiction  of  the  tool  used  in  stirring  the  metal,  and 
through  which  the  workman  can  observe  the  state  of  the  fm- 
nace.  It  may  be  closed  air-tight. 

The  Tap-hole.,  through  which  the  slag,  or  tap-cinder,  is  with- 
drawn from  the  hearth,  is  placed  below  the  door-sill.  It  is 
plugged  iip  with  sand.  A portion  of  the  cinder  also  overflows 
the  flue-bridge,  and  runs  down  the  inclined  surface  of  the  flue 
to  the  bottom  of  the  stack,  h. 

75.  Process  of  Puddling. — Although  the  process  of  pud- 
dling is  susceptible  of  considerable  modification  according  to 
the  nature  of  the  pig-metal  employed  and  that  of  the  iron  wliich 
it  is  desired  to  produce,  it  may  be  generally  stated  to  include 
the  following  operations : 

1st.  Melting  down  of  the  charge  with  or  without  the  previ- 
ous heating. 

2d.  Incorporation  of  osydizing  fluxes  with  the  charge  at  a 
low  heat. 

3d.  Elimination  of  carbon  by  stmlng  the  contents  of  the 
furnace  at  a high  temperatm’e. 

4th.  Consolidation  of  the  reduced  fion  to  masses  or  balls  fit 
for  hammerino;. 

O 


CANNON  METALS. 


25 


7G.  CnAKGiNG  THE  FtTKXACE. — Pieces  of  metal  are  succes- 
sively introduced  with  a long  shovel,  and  laid  one  over  another 
on  tlie  sides  of  the  hearth  in  the  form  of  piles  rising  to  the 
roof,  the  middle  being  left  open  for  puddling  the  metal  as  it  is 
successively  fused.  The  piles  are  kept  separate  to  give  free  cir- 
culation of  air  round  the  metal.  The  working-door  of  the  fur- 
nace is  now  closed,  fuel  is  laid  on  the  grate,  and  the  mouth  of 
the  fireplace  is  filled  up  with  coal ; at  the  same  time  the  damper 
is  entirely  opened. 

In  puddling  refined  metal,  or  in  dry  puddling,  the  furnace 
is  charged  with  metal  alone,  hut  in  puddling, gray  metal,  that  is,  in 
wet  puddling,  or  boiling,  as  it  is  tai'meU,  forge-cinder  is  charged 
along  with  the  metal,  and  the  temperature  rises  much  higher. 

77.  PuDDLiNG-TooLS. — ^The  tools  employed  are  principally 
of  two  kinds,  namely,  long,  straight,  chisel -edged  bars,  or  pad- 
dles, and  hooked  bars  with  similar  fiat  ends,  called  rccbbles. 
The  number  of  tools  used  in  the  working  of  one  charge  depends 
on  the  quality  of  the  iron,  and  may  vary  from  four  to  eight, 
according  to  the  amount  of  work  required.  When  withdrawn 
from  the  furnace,  the  points  are  coated  with  molten  cinder, 
which  is  removed  by  quenching  the  bar  in  a cistern  of  cold  water. 

78.  In  order  to  lessen  the  great  amount  of  labor  involved  in 
working  the  chaige,  various  mechanical  appliances  have  been 
proposed  in  substitution  for  manual  puddling,  but  these  as  yet 
have  not  been  adopted  to  any  great  extent.  They  may  be  gen- 
erally classified  under  two  heads,  namely,  those  imitating  the 
motions  of  hand-sthring,  and  those  usina:  rotatina;  or  oscillatina: 

o o o 

hearths. 

Dank’s  rotatory  puddling-furnace  is  the  most  successful  of 
these,  and  is  being  introduced  quite  extensively.  It  produces  a 
better  quality  of  iron  with  much  less  labor,  and  in  less  time 
than  is  possible  by  hand-puddling. 

79.  Manipulation  of  the  Molten  Iron. — When  the  metal 
begins  to  soften,  the  workman  or  puddler  introduces  the  rab- 
ble through  the  stopper-hole  for  the  purpose  of  working  the 
metal.  The  amount  of  handling  required  in  this  part  of  the 
process  dejiends  upon  the  nature  of  the  iron  operated  upon. 

80.  White  or  Refined  Iron. — When  this  is  used  it  requires  a 
continuous  operation,  which  calls  for  much  care  and  skill  on  the 
part  of  the  w’orkman.  The  pieces  of  metal  that  begin  to  melt 
are  detached  from  the  piles  with  the  rabble,  and  new  surfaces 
opposed  to  the  action  of  the  heat ; as  it  softens  it  is  removed  from 
the  vicinity  of  the  fire-bridge,  to  prevent  the  metal  from  run- 
ning together. 

When  the  whole  of  the  metal  is  reduced  to  a pasty  condition, 


2G 


NAVAL  OKDNANCE  AND  GUNNERY. 


the  temperatiu-e  of  the  furnace  is  lowered  to  prevent  its  heconi- 
iug  more  fluid.  The  puddler  now  works  about  with  his  rabble 
the  clotty  metal,  which  swells  up  exhibiting  a kind  of  fermenta- 
tion, occasioned  by  the  discharge  of  carbonic  oxide,  burning  with 
a blue  flame  as  if  the  bath  were  on  fire.  The  metal  becomes 
finer  by  degrees  and  less  fusible,  or,  in  the  language  of  the  work- 
man, it  begins  to  dry.  The  disengagement  of  carbonic  o.xide 
diminishes  and  soon  stops.  The  workman  continues  meanwhile 
to  puddle  the  metal  till  the  whole  charge  is  I'educed  to  the  state 
of  incoherent  sand ; the  damper  is  then  progressively  opened. 
With  the  return  of  heat  the  particles  of  metal  begin  to  aggluti- 
nate, the  charge  becomes  more  difficult  to  raise,  or,  in  the  lan- 
guage of  the  workman,  it  works  heavy. 

The  refining  is  now  finished,  and  nothing  remains  but  to 
gather  the  mon  mto  balls. 

81.  Gray  Pig-iron. — With  this  variety  of  iron,  which  re- 
quires a higher  temperature  for  fusion,  but  which  runs  very 
liquid,  the  fragments  may  be  melted  clown  without  being  moved, 
if  the  furnace  is  sufficiently  hot. 

Oxydizing  agents  are  charged  with  the  iron.  In  order  to 
bring  about  the  reaction  of  the  slag  upon  the  melted  metal  it  is 
necessary  to  incorporate  the  whole  contents  of  the  furnace  well 
together  after  melting.  For  this  purpose  the  temperature  is 
lowered  by  checking  the  draught  or  even  throwing  water  upon 
the  metal,  the  charge  being  stirred  at  the  same  time. 

The  slag  is  also  reduced  to  a more  basic  condition  by  the 
addition  of  scale.,  or  mill-einder,  to  compensate  for  the  silica 
produced  from  the  oxydation  of  silicon  in  the  pig. 

When  the  mixture  is  complete  and  the  mass  somewhat  stif- 
fened, the  reaction  of  the  oxide  and  silicate  of  u-on  upon  the 
combined  carbon  is  apparent  by  the  escape  of  blue  flames  of  car- 
bonic oxide,  and  as  the  teinj^erature  is  increasdtl  by  opening  the 
damper  the  whole  surface  commences  to  boil,  from  the  rapid 
escape  of  gas,  and  at  the  same  time  a portion  of  the  molten  slag 
flows  out.  The  action  is  facilitated  by  constant  sthring  with 
the  rabble. 

As  the  carbon  diminishes  the  ebullition  becomes  less  violent, 
and  the  bath  from  its  reduced  fusibility  in  spite  of  the  high  tem- 
perature begins  to  stiffen,  and  malleable  iron  separates,  or,  as  it 
is  called,  comes  to  naUire. 

At  this  point  of  the  process  the  whole  contents  of  the  furnace 
require  to  be  well  stirred  and  broken  iqa,  so  that  every  part  may 
be  brought  imder  the  influence  of  the  high  temperatiu-e.  The 
reduced  mass  is  subject  to  a final  heat  in  order  to  facilitate  the 
separation  of  the  cinder  by  rendering  it  perfectly  fluid. 


CANNON  JIETALS. 


27 


82.  The  Puddle  Balls. — Tlie  last  operation  consists  in 
forming  np  the  balls,  Avhich  is  done  by  detaching  from  the  re- 
duced iron  masses  from  sixty  to  eighty  pounds  weight  each,  and 
pressing  them  together  with  the  tool  until  they  are  sufficiently 
coherent  to  be  moved  without  falling  to  pieces.  This  may  be 
done  either  by  pressing  against  the  bottom  and  sides  of  the  fur- 
nace, or  by  a rolling  motion,  the  iron  being  gathered  up  around  a 
small  nucieus  like  a snow-ball. 

As  soon  as  a ball  is  made,  it  is  placed  close  against  the  fire- 
bridge to  keep  it  hot  and  out  of  the  draught  of  air  between  the 
working-door  and  the  line ; the  second  is  proceeded  with  until 
the  whole  of  the  charge  has  been  balled  up  ; the  stopper-hole  is 
then  closed,  and  the  final  heat  is  given  to  facilitate  the  operation 
of  shirt  gling. 

The  removal  of  the  balls,  which  are  of  a roughly  spherical 
form,  after  they  are  drawn  to  the  working-door  with  the  tool,  is 
effected  by  means  of  a long  pair  of  tongs  with  curved  jaws. , 
They  are  first  lifted  to  the  iron  table  in  front  of  the  working- 
door,  and  afterwards  either  dragged  along  the  floor  or  carried  on 
a wrought-iron  truck  to  the  hammer,  or  such  other  maehme  as 
may  be  employed  for  shingling. 

83.  SiiiNGLTNG,  OK  Bloomixg,  is  the  process  of  converting 
the  puddle  balls  into  malleable  stuff  by  hammering  or  com- 
pressing. 

A Bloom  is  a rough  lump  or  bar  of  wrought-iron  which 
results  from  the  slfingliug  process. 

8d.  Shingling  Machines. — The  machines  used  in  the  com- 
])ression  and  welding  of  the  rough  balls  of  malleable  iron  into 
blooms  are  of  two  different  kinds,  namely,  hammers  and  squeez- 
ers.^ the  former  acting  by  percussion,  and  the  latter  by  compres- 
sion. In  addition  to  these,  it  is  usual  to  reduce  the  blooms  so 
obtained  to  short  rough  bars  by  passing  them  at  the  same  heat 
throtigh  a rolling-mill. 

85.  The  Flxisiied  Bak. — The  rough  bars,  or  slabs,  of  malle- 
able iron  obtained  in  the  process  of  puddling  and  shingling, 
require  to  be  subjected  to  other  treatment  in  order  to  produce 
finished,  or  merchant  iron. 

For  this  purpose  they  are  cut  into  short  lengths,  which  are 
made  into  nearly  cubical  packets  or  piles  and  subjected  to  a 
further  consolidation  by  hammering  and  rolling,  at  a welding- 
heat,  imtil  a bar  Avith  a uniformly  smooth  surface,  free  from 
flaws  or  cracks,  is  obtained. 

86.  Eolling-mills. — These  are  used  in  the  production  of 
finished  iron  from  the  blooms.  In  its  simplest  form  a rolling- 
mill  consists  of  two  cast-h'on  cylinders  placed  with  them  axes 


28 


NAVAL  ORDNANCE  AND  GUNNERY. 


horizontally  one  above  the  other,  and  connected  by  spur-geaiing, 
so  as  to  revolve  at  the  same  velocity,  (big.  7.) 

The  surface  of  the  rolls  may  be  either  smooth,  as  is  the  case 

in  the  plate-mfUs,  or 
grooved  into  various 
patterns,  as  in  those 
used  for  the  produc- 
tion of  merchant 
bars.  (Fig.  7.) 

The  reduction  in 
the  size  of  the  bloom 
is  effected  by  regu- 
lating the  vertical 
distance  between  the 
two  rolls,  by  the  use 
of  grooves  diminish- 
in<y  re^rularlv  in  size, 
or  by  a combination 
of  both  methods. 

As  the  direction  of  rotation  of  the  rolls  is  constant  under 
ordinary  circumstances,  it  is  necessary  after  the  bar  has  passed 
tlirough  one  groove,  to  return  it  by  lifting  it  over  the  top  roll, 
in  order  to  bring  it  in  position  to  pass  through  the  next  smaller 
one,  and  so  on  in  succession.  This  may  be  easily  done  with 
blooms  of  small  size,  hut  it  is  attended  with  considerable  diffi- 
culty when  it  is  required  to  handle  large  masses  of  iron,  and  in 
any  case  gives  rise  to  a certam  loss  of  time  and  consequent  waste 
of  iron  by  scaling,  from  exposure  to  the  atmosphere  in  a highly 
heated  condition  for  a longer  time  than  is  absolutely  required. 

Very  heavy  mills,  such  as  are  used  for  armor-plates,  require 
to  be  reversed  at  each  passage  of  the  pile,  the  distance  between 
the  rolls  being  diminislied  each  time. 

87.  Reheating.— The  operation  of  reheating  may  be  per- 
formed in  several  different  ways.  The  plan  most  generally 
adopted  is  in  a reverberatory  furnace  known  as  the  mill^fumace, 
not  unlike  in  external  appearance  to  that  used  in  puddling. 
The  bed  is  made  of  tire-brick  covered  with  a thick  coating  of 
sand.  On  it  the  piles  are  placed,  and  brought  rapidly  up  to  a 
welding-heat,  for  rolling. 

When  the  dimensions  of  the  pile  are  such  as  to  require  sev- 
eral passages  tlirough  the  rolling-mill,  in  order  to  reduce  it  to 
the  proper  section,  it  is  often  necessary  to  subject  it  to  a second 
heating. 

In  this  process  loss  by  oxydation  consequent  upon  unneces- 
sary exposure  must  be  prevented  as  much  as  possible.  Oxide 


Fig.  7. 


CANXOJ}'  3IET.\LS. 


29 


of  iron  in  tlie  form  of  scales  forms  very  rapidly  when  a heated 
bar  is  exposed  to  the  air. 

Those  produced  in  the  rolling-mill  are  called  mill,  or  forge, 
cinders,  and  are  much  used  in  puddling  by  the  wet  way,  or  pig- 
boiling. 

88.  PiLixG. — The  amount  of  work  put  into  bar-iron  varies 
with  the  quality.  For  the  common  kinds,  puddled  bars,  or  ITo. 
1 iron,  cut  into  lengths,  are  phed,  and  wlien  brought  to  a weld- 
ing-heat, are  rolled  off,  either  with  or  without  first  being  worked 
into  a bloom  under  the  hammer.  More  usually,  however,  the 
u’on  of , second-rolling,  or  Mo.  2,  is  employed  at  the  top  and  bot- 
tom plates  of  the  piles 
when  making  finished 
No.  3,  or  best  iron.  Be- 
yond this,  if  further 
piled  and  welded,  the 
iron  is  distinguished  as  • Fig.  8. — Sections  of  pUes  for  finished  iron. 
hest-hcst  and  trebledest, 

according  to  the  number  of  heatings  and  weldings  to  which  it 
has  been  subjected.  (Fig.  8.) 

The  harder  and  more  granular  kinds  of  iron  are  worked 
almost  exclusively  under  the  hammer,  the  rolling-mill  being 
only  used  in  giving  the  proper  figure  to  the  bar  at  the  finishing 
stage. 

The  piles  for  the  heavier  classes  of  plates  are  built  up  of 
layers  of  bars,  placed  alternately  across  each  other,  instead  of 
having  their  longer  sides  parallel,  as  in  the  ease  of  ordinary  bar- 
iron,  and  the  covering  slabs,  or  top  and  bottom  plates,  are  flat 
bars  of  greater  width  than  the  intermediate  layers. 

89.  Examples  of  Piling. — The  following  examples,  from 
Bauerman,  give  the  details  of  manipulation  in  rolling  bars. 

For  bars  of  one  inch  square  the  pile  was  made  up  of  six  bars, 
each  three-Cjuarters  of  an  inch  thick,  and  four  inches  wide. 
When  at  a proper  welding-heat  it  was  passed  eleven  times 
through  the  rolls. 

Tlie  loss  on  the  weight  of  the  pile  was  about  fifteen  per  cent., 
caused  by  oxydation,  and  in  crop-ends  and  waste  hi  rolling. 

Crop-ends. — The  waste  material,  or  scraps,  produced  by 
shearing  in  finishing  bar-iron  is  called  crop-ends.  They  are 
reworked  or  utilized  in  many  ways. 

For  boiler-plates  measuring  six  feet  long  by  three  feet 
broad  and  three-sixteenths  inch  thick,  the  pile  was  made  twenty 
inches  long,  six  to  seven  inches  high,  and  twelve  inches  broad. 

The  whole  of  the  work  was  clone  at  one  heat,  the  pile 
reduced  to  a roughly  squared  bloom  by  passing  lengthways 


30 


NAVAL  ORDNANCE  AND  GUNNERY. 


throngli  three  grooves  in  the  hlooming-rolls,  then  four  times 
through  tlie  plate-ronghing  rolls,  in  the  direction  of  the  breadth, 
which  draws  it  into  a thick  squared  plate,  and  finally  thi  ee  times 
lengthways  through  the  finishing-rolls. 

The  difference  in  weight  between  the  finished  plate  and  the 
rough  bars  taken  for  the  pile  is  about  twenty  per  cent.,  which 
includes  the  waste  in  reheating  and  scraps  produced  in  shearing 
the  edges  to  the  proper  size. 

90.  Rolled  Armor^jlates  are  put  together  as  follows  : The 

balls  from  the  puddling-fnmace  are  shingled,  and  rolled  to  slabs 
about  twelve  inches  broad,  thirty  inches  long,  and  one  inch 
thick.  Five  or  six  of  these  slabs  are  in  a second  heat  rolled  to  a 
slab  about  four  feet  square.  At  the  third  piling  five  or  six  slabs 
of  the  second  heat  are  welded  and  rolled  into  a plate  about 
eight  feet  long,  four  and  one-half  feet  broad,  and  two  and  one- 
half  inches  thick,  weighing  rather  more  than  30  cwt.,  and  made 
np  of  between  twenty-five  and  thirty-six  original  inch-slabs  of 
ISIo.  1 iron. 

Fo)’  the  finished  plates  of  four  and  one-half  or  five  and  one- 
half  inches  in  thickness  four  of  the  large  30  cwt.  plates  are  piled 
together  and  reheated. 

The  door  of  the  furnace  is  placed  parallel  to  the  axis  of  the 
rolling-mill,  and  the  pile,  when  sufficiently  heated,  is  drawn  for- 
ward with  tongs,  and  received  on  a truck  which  nrns  upon  a 
railway  directly  to  the  rolls.  A similar  truck  is  placed  on  the 
opposite  side  of  the  mill,  their  surfaces  being  supplied  with  fric- 
tion-rollers, so  that  the  pile  may  be  easily  pushed  between  the 
rolls,  through  which  it  is  passed  forwards  and  backwards,  by 
reversing  the  rolls,  until  it  is  reduced  to  the  proper  thickness. 

It  will  be  seen  that  the  finished  plate  consists  of  between 
100  and  Hi  slabs,  compressed  to  about  one-twentieth  or  one- 
thirtieth  of  their  original  thickness. 

91.  Peculiakities. — By  the  processes  described,  the  cast-iron 
has  been  converted  from  a fusible,  hard,  and  brittle  substance 
into  a tough  and  elastic  bar.  It  has  been  rendered  malleable, 
which  is  the  property  of  extending  or  spreading  under  the 
hammer  without  cracking  ; ductile,,  a iDroperty  similar  to  malle- 
ability, whereby  it  may  be  drawn  out  into  wire  without  break- 
ing, and  its  tenacity  has  been  iiicreased,  a property  which  ena- 
bles it  to  sustain  a very  great  pressure  or  force  without  cmsh- 
ing  or  breaking. 

In  a cold  state  it  is  hard  and  stubborn,  but  at  a red  heat  it  is 
soft  and  pliable,  and,  at  a white  or  sparkling  heat  it  may  be 
welded  to  itself  or  to  steel,  which  is  one  of  its  greatest  advan- 
tages. 


CAXNON  METALS. 


31 


93.  The  great  improvement  in  the  strength  of  malleahle  iron 
by  the  processes  of  fagoting  and  rolling  has  been  more  satisfac- 
torily established  by  experience  than  explained  by  theory." 
One  obvions  effect  of  the  violent  compression  between  the  rollers 
is  the  squeezing  out  of  slag,  which  is  liable  to  become  entan- 
gled in  the  iron  during  hammering  and  rolling  of  the  balls 
taken  from  the  puddling-furnace.  The  occurrence  of  small 
masses  of  slag  in  malleable  iron  is  not  an  uncommon  cause  of 
weakness,  each  particle  of  slag  giving  rise  to  a flaw  in  the 
metal.  In  the  process  of  reheating  the  bars  this  slag  is  melted, 
and  may  then  be  squeezed  out  by  the  action  of  the  rollers. 

A marked  diminution  in  the  proportions  of  carbon  and  silicon 
present  in  the  ii’on  is  also  effected  cluring  the  process,  as  shown 
by  the  following  results  of  chemical  analysis  : 

In  too  parts.  Carbon.  Silicon. 

Puddled  bar 0.296  0.120 

Best  bar 0.111  0.088 

This  may  be  explained  by  the  action  of  the  oxide  of  iron 
formed  upon  the  surface  of  the  bar  during  exposure  to  air  at  a 
welding-heat.  ' 

The  rolling  of  several  bars  into  a single  bar  would  render 
the  structure  of  the  metal  uniform,  so  that  the  bar  would  be 
equally  strong  throughorrt. 

During  the  operation  of  fagoting  and  rolling  the  iron 
acquires  a remarkable  fibrous  structure,  so  that  if  a bar  of  the 
best  iron  be  notched  with  a chisel,  and  broken  across  by  a 
steady  pressure,  the  fracture  will  present  a stringy  appearance, 
resembling  that  of  a green  stick ; whilst  a puddled  bar  thus 
treated  would  exhibit  a crystalline,  shining  fracture,  not  unlike 
that  of  cast-iron.  That  this  nerve,  or  reed,  as  the  fibrous  struc- 
ture is  sometimes  called,  should  materially  increase  the  resist- 
ance of  a bar  to  any  transverse  strain,  can  readily  be  believed, 
for  such  a bar  resembles  a bundle  of  wires  firmly  bound  to- 
gether, whilst  a crystalline  bar  must  be  regarded  as  composed 
of  a number  of  particles  of  iron  stuck  together  in  a confused 
manner. 

93.  But  with  our  present  imperfect  acquaintance  with  the 
mutual  relations  and  movements  of  the  individual  particles 
composing  a solid  mass,  it  is  not  easy  to  give  a satisfactory 
explanation  of  the  production  of  the  fibrous  structm’e  by  rolling 
the  softened  bars  in  the  direction  of  their  length. 

Much  less  can  we  explain  the  circumstance,  which  appears 


Bloxam. 


32 


NAVAL  OEDNANCE  AND  GUNNERY. 


to  have  been  satisfactorily  established,  that  this  fibrons  structure 
is  liable  to  reconversion  into  the  crystalline  structure  if  the  iron 
be  subjected  to  a long  succession  of  powerful  vibrations. 

The  deterioration  in  the  strength  of  bar-iron  by  often 
repeated  forging  under  the  hammer  is  commonly  explained  as 
resulting  from  this  change  in  structure,  and  axles,  girders,  etc., 
originally  made  of  bbrous  iron,  are  said  to  have  snapped 
unexpectedly,  exhibiting  a crystalline  structure.  Hence,  in 
cases  where  the  iron  is  to  be  exposed  to  much  vibration,  a fine- 
grained wrougbt-iron,  richer  in  carbon,  is  preferred  to  a fibrous 
iron. 

94.  In  drawing  any  inference  as  to  the  quality  of  wrougbt- 
iron  from  the  character  of  its  fracture,  it  is  most  important  that 
the  mode  of  breaking  it  should  be  taken  into  account,  for  it  is 
found  that  a bar  or  plate  which  exhibits  a fine  bbrous  struc- 
ture, Avhen  broken  by  bending,  appears  crystalline  when  sud- 
denly snapped,  or  when  broken  by  a blow  from  a shot ; and  it 
is  probable  that  a want  of  attention  to  this  has  given  rise  to 
many  of  the  contradictory  statements  with  respect  to  alterations 
in  the  structure  of  wrougbt-iron  under  various  conditions. 

95.  Yariation  in  Quality. — Forged,  or  wrougbt-iron,  like 
cast-iron,  varies  greatly  in  quality  according  to  purity  and  treat- 
ment in  its  manufacture. 

It  may  be  divided  generally  into  four  different  kinds. 

First.  Iron  which  is  tough  and  malleable  at  all  tempera- 
tures. This  is  the  best  and  most  useful,  as  it  may  be  bent  in 
any  direction  without  breaking,  both  when  it  is  hot  and  when 
it  is  cold. 

It  may  be  known  generally  by  the  equable  surface  of  the 
forged  bar,  which  is  free  from  cross  fissures,  or  cracks,  in  the 
edges,  and  by  a clear,  white,  small  grain,  or  rather  fibrous  te.x- 
ture.  The  best  and  toughest  iron  is  that  which  has  the  best 
welding  properties,  and  which  bears  the  highest  heat  without 
injury,  and  which  has  most  fibrous  texture,  and  is  of  a clear 
grayish  color. 

Second.  The  next  best  iron  is  that  which  has  a texture  con- 
sisting of  clear  wliitish  small  grains  intermixed  with  fibres.  It 
is  tough  and  malleable  at  all  temperatures,  bears  a moderately 
high  degree  of  heat  without  injury,  and  has  good  welding  prop- 
erties. 

Third.  Another  kind  of  iron  is  tough  when  heated,  hut  brit- 
tle when  it  is  cold,  so  brittle  that  it  will  sometimes  break  with  a 
single  blow  of  the  hammer,  or  by  a sudden  jerk,  which  makes  it 
unfit  for  several  kinds  of  work  where  life  and  property  are 
dependent  upon  it;  but  for  some  kinds  of  work  that  are  to  be 


CANNON  METALS. 


33 


exposed  to  tlie  weather  it  is  very  useful,  as  it  will  resist  the 
action  of  the  atmosphere  better  than  the  other  kinds.  It  may 
generally  he  distinguished  by  a texture  consisting  of  large  shin- 
ing plates,  without  any  fibres,  and  is  called  cold-short  iron. 

Fourth.  Hot-short,  or  red-short,  iron.  This  is  extremely 
brittle  when  hot,  and  malleable  when  cold.  It  will  not  bear 
bending  without  breaking,  or  piercing  without  splitting,  and  it 
is  never  used  for  superior  kinds  of  work. 

But  owing  to  its  being  much  cheaper  than  the  superior  kinds, 
and  being  very  tough  and  ductile  in  its  cold  state,  for  many  pur- 
poses it  is  a very  useful  iron. 

On  the  surface  and  edges  of  the  bars  of  this  kind  of  iron 
cracks  or  fissures  may  be  seen,  and  its  internal  a]3pearance  is 
earthy,  dull,  and  dark. 

90.  Welding  is  that  0])eration  by  which  pieces  of  iron,  or 
steel,  or  steel  and  iron,  are  heated  nearly  to  a state  of  fusion,  and 
appearing  to  be  covered  with  a strong  glaze,  or  varnish,  are 
brought  together,  and  united  by  repeated  blows  of  the  hammer, 
or  under  pressure,  and  the  union  not  to  be  perceived. 

The  heat  required  for  welding  iron  varies  in  some  degree 
with  the  purity  of  the  iron.  Pure  fibrous  iron  will  bear  almost 
any  degree  of  heat  without  much  injury,  if  not  too  long  exposed 
to  the  heat,  while  impure  iron  bears  but  a moderate  degree  of 
heat  without  being  melted  or  burnt. 

97.  Porter-har.  When  a mass  is  too  large  to  be  handled  con- 
veniently with  the  tongs,  a large  iron  rod  is  welded  to  it,  to 
serve  as  a porter,  or  guide-rod.  Sometimes  a part  of  the  porter- 
bar  is  made  to  form  the  core  of  the  forging,  and  the  slabs  of 
iron  Avhich  form  the  forging  are  welded  and  built  upon  the 
bar.  When  the  mass  of  iron  is  too  large  to  be  handled  by  the 
forge-man,  it  is  supported  by  a crane,  which  serves  to  swing  it 
from  the  fire  to  the  hammer. 

98.  Upsetting. — When  it  is  required  to  thicken  any  part  of 
a bar  of  iron  without  welding,  it  is  done  by  the  operation  called 
“ lipsetting.”  This  consists  in  giving  it  the  welding-heat  at  the 
part  to  be  thickened,  and  while  one  end  rests  upon  the  anvil 
hammering  at  the  other  till  the  required  size  is  produced. 
When  the  bar  is  large,  if  it  be  lifted  and  jumped  upon  the  anvil 
its  own  weight  will  supply  the  required  force  for  upsetting. 
When  it  is  required  to  weld  two  bars  of  iron  together  the  ends 
are  first  upset,  or  made  thicker. 

99.  Scarfing. — Each  end  is  then  bevelled  off  to  a thin  edge, 
called  scarfing  ; the  two  ends  are  then  placed  in  the  fire,  and 
raised  to  a welding-heat,  or  nearly  to  a state  of  fusion  ; care  is 
required  that  both  arrive  at  the  proj)er  heat  at  the  same  time. 

3 


NAVAL  ORDNANCE  AND  GUNNERY. 


Si 


The  bars  may  in  part  be  prevented  from  Avasting  by  taking  care 
to  supply  them  at  the  heated  part  with  powdered  glass  or  sand 
just  before  they  arrive  at  the  welding-heat.  The  sand  or  other 
material  melts  on  the  surface  of  the  iron,  and  serves  to  form  a 
flux,  or  fluid  glass,  Avhich  protects  the  iron  from  the  imparities 
of  the  fuel,  and  defends  it  from  the  air,  at  the  same  time  unit- 
ing with  and  removing  the  oxide  which  may  have  been  formed 
on  the  heated  scarfs. 

When  the  bars  have  obtained  the  welding-heat  they  are 
removed  fi'om  the  Are  with  the  utmost  dispatch,  and  struck 
across  the  anvil  to  remove  as  far  as  possible  all  scales  and  dirt 
which  would  hinder  their  rmiting ; they  are  then  placed  in  con- 
tact at  the  heated  part  and  hammered,  the  superfluous  cinder  is 
squeezed  out  as  the  clear  parts  are  brought  together,  and  the 
hammering  continued  until  no  visible  seam  or  fissure  remains. 

100.  In  welding  large  pieces  the  process  is  more  diflicult. 
Several  minutes  must  sometimes  elapse  before  the  parts  can  be 
brought  together  ; meanwhile  thick  scales  are  forming  on  the 
exposed  heated  surfaces. 

The  rapidity  with  which  iron  at  a welding-heat  becomes 
oxydized  is  strikingly  illustrated  in  the  operation  of  “ patting  ’’ 
the  Armstrong  tubes  after  they  are  welded  end  to  end.  (Art. 
654.) 

The  scales  that  form  on  the  inside  of  the  tube  are  jarred  off 
at  every  stroke  of  the  hammer  upon  the  outside,  thus  exposing 
fresh  surfaces  to  oxydation.  At  the  end  of  the  process  the 
scales  form  a pile  in  the  tube  several  inches  in  depth. 


Section  lY. — Steel. 

101.  Peculiaeities. — Those  varieties  of  iron  in  which  the 
amount  of  carbon  is  above  the  maximum  of  malleable  and  beloAv 
the  minimum  of  cast-metal,  are  known  as  steel.  The  distinguish- 
ing property  of  this  class  of  products  is  the  capability  of  being 
hardened  or  softened  at  pleasure  by  sudden  or  slow  cooling  by 
the  process  knoAvn  as  tempering. 

Being  intermediate  in  position  between  wrought  and  cast- 
iron,  steel  is  both  fusible  and  malleable,  but  requires  a higher 
temperature  for  fusion  than  cast-iron,  and  greater  compressing 
power,  owing  to  its  loAver  welding  temperature,  than  malleable 
iron. 

102.  Steel  is  a combination,  or  alloy,  of  iron  that  Avill 
forge,  harden,  and  temper. 

There  are  various  kinds  of  steel,  such  as  Carloon  Cast-steel, 


CAXNO^r  IIETALS. 


35 


Tuncjstein  Cast-steely  Chrome  Castrsteel,  Cyanogen  Cast-steel, 
and  Titanium  Castrsteel ; aud  several  other  metals  have  beeu 
allo_yed  with  Iron  to  make  Steel. 

There  is  also  Blistered  Steel,  which  is  made  from  malleable 
bai'-iron,  by  a pj’ocess  called  Cementation  / German  Steel,  which 
is  made  directly  from  the  ore,  and  sometimes  from  Pig-iroo,  in 
the  Catalan  forge  ; and  steel  which  is  made  by  other  processes. 

103.  The  line  between  Cast-iron  and  Steel  is : when  it  is 
capable  of  being  forged,  it  is  Steel ; and  when  it  will  not  forge, 
it  is  Cast-iron.  And  the  line  between  Malleable  Iron  and  Steel 
is  : v.dien  it  will  harden  and  temper,  it  is  Steel ; and  when  it  will 
not  harden  and  temper,  it  is  ^Malleable  Iron. 

Cast-steel  will  harden  slightly  wdien  it  contains  from  0.25 
per  cent,  to  0.30  per  cent,  of  carbon,  and  ceases  to  be  capable 
of  forging  if  it  contains  much  more  that  1.75  per  cent,  of 
carbon. 

10-1.  Bigli  and  Low  Steel. — Those  varieties  that  are  the 
richest  in  carbon  are  the  hardest  and  most  fusible,  and  are 
known  as  high  steels,  or  strong  steels,  while  those  that  are  nearer 
malleable  iron  in  composition  are  distinguished  as  low  steels,  or 
mild  steels,  or  homogeneous  metals. 

105.  How  Obtained. — Steel  may  be  obtained  by  a variety 
of  processes,  of  greater  or  less  complexity,  from  either  cast  or 
wrought-iron.  These  processes  are  directly  opposed  to  each 
other. 

First,  by  working  pig-iron  which  contains  too  much  carbon, 
in  a suitable  furnace  until  such  carbon  is  reduced  to  that  quan- 
tity required  to  constitute  steel ; or,  second,  by  heating  bar-iron, 
in  contact  with  charcoal,  until  it  has  absorbed  that  quantity  of 
carbon  wdiich  may  be  necessary. 

The  progress  made  within  the  past  few  years  in  the  manu- 
facture of  steel,  has  been  such  as  to  indicate  that  in  a very  short 
time  it  may  be  produced  as  cheaply,  if  not  cheaper,  than 
wrought-iron  is  at  present.  In  fact,  steel  is  already  taking  the 
place  of  iron,  for  various  industrial  purposes,  to  a very  great 
extent ; and  inventions  of  new  processes  and  apparatus  for  its 
manufacture,  and  improvements  in  those  already  in  use,  have 
become  so  common  as  to  attract  but  little  attention. 

lOG.  Classification.— Steel  may  be  classed  into  three  kinds : 

First.  Natural  Steel,  whish  is  manufactured  from  pig-iron 
direct. 

Second.  Cemented  Steel,  or  converted  steel,  which  is  pro- 
duced by  the  carbonization  of  wrought-iron. 

Third.  Cast-steel,  which  is  produced  by  the  fusion  of  either 
natural  or  converted  steel. 


36 


NAVAL  ORDNANCE  AND  GUNNERY. 


107.  Puddled  Steel. — This  is  a natural  steel,  made  in  tlie 
puddling-fuTiiace  by  a modification  of  the  puddling  process. 

The  process  of  making  puddled  steel  may  be  described  in  a 
general  way  as  follows ; Cast-iron  contains  from  three  to  five 
per  cent,  of  carbon ; ordinary  steel  contains  from  three-fourths 
to  one  per  cent,  of  carbon ; while  wrought-iron  contains  but  a 
trace.  In  changing  from  cast  to  wrought-iron  in  a puddling- 
furnace,  the  pig-metal  passes  through  the  state  of  steel,  that  is 
to  say,  it  is  steel  before  it  is  Avrought-iron.  Isow  making  pud- 
dled steel  is  simply  stopping  the  common  puddling  process,  just 
at  the  moment  Avhen  the  decarbonizmg  mass  under  treatment  is 
in  the  state  of  steel. 

Several  modifications  in  furnaces  and  processes  have  been 
patented,  and  various  fluxes,  especially  manganese,  are  difierent- 
ly  used,  by  diflerent  manufacturers. 

108.  Cemented  Steel. — The  production  of  steel  by  cemen- 
tation consists  essentially  in  the  exposure  of  bars  of  malleable 
iron,  in  close  contact  Avith  charcoal,  to  a high  and  long-continued 
heat,  the  air  being  excluded. 

109.  CoNVEETiNG-FUKNACE. — The  furuacc  in  Avhich  iron  is 
cemented  and  converted  into  steel,  is  called  a Converting-fur- 


Fig.  9. — Cementation  Furnace  for  converting-  Bar-iron  into  Steel. 

nace.  (Fig.  9.)  It  has  the  form  of  a large  oven,  constracted  so 
as  to  form  in  the  interior  of  the  OA-en  tAvo  large  and  long  cases, 
commonly  calledyiofe,  and  built  of  good  fire-brick. 

110.  Pacldng  the  Pots. — Into  each  of  these  pots  layers  of 
the  purest  malleable-iron  bars  and  layers  of  powdered  charcoal 
are  packed  horizontally,  one  upon  the  other,  to  a proper  height 
and  Cjuantity,  according  to  the  size  of  the  pots,  leaA-ing  room 
every  Avay  for  the  expansion  of  the  metal  Avhen  it  becomes 
heated.  The  bars  are  cut  to  certain  lengths,  according  to  the 
lengths  of  the  pots. 


CAXISTON  3IETALS. 


37 


Three  or  four  of  the  bars  are  placed  in  such  a manner  that 
they  can  he  drawn  out  at  any  period  of  the  process,  through  a 
small  hole  in  the  end  of  the  pot,  and  examined.  After  the 
packing  of  the  pots  is  completed,  the  tops  are  covered  with  a 
bed  of  sand  or  clay,  to  confine  the  carbon  and  exclude  the  air. 

111.  Process  of  Cementaiion. — All  the  open  spaces  of  the 
furnace  are  then  closed,  and  the  fire  kindled  ; the  flame  passes 
between,  under,  and  around  these  pots  on  every  side,  and  the 
whole  is  raised  to  a considerable  intensity  of  heat.  This  heat 
is  kept  up  for  eight  or  ten  days,  according  to  the  degree  of 
hardness  required,  the  hardest  quality  for  meltmg  purposes  re- 
quiring the  longest  time. 

The  progress  of  the  conversion  is  determined  by  the  appear- 
ance of  the  trial  bar  ; the  first  is  taken  out  after  about  a week’s 
firina:.  When  there  is  no  longer  an  unaltered  kernel  of  soft  iron 
apparent  in  the  centre,  the  conversion  is  considered  to  be  com- 
plete, the  fire  is  allowed  to  go  down,  the  furnace  is  left  to  cool, 
and  the  cemented  bars  are  then  after  several  days  withdrawn. 

112.  The  physical  properties  of  the  iron  are  considerably 
modified  by  conversion : the  color  of  the  fractured  surftice 
changes  from  the  original  bluish  tinge  of  malleable  iron  to  a 
somewhat  reddish-white,  and  the  lustre  is  considerably  dimin- 
ished ; the  texture,  which  was  originally  fibrous,  has  become 
granular,  and  is  in  all  cases  scaly-crystalline. 

The  finer  the  grain,  and  the  darker  the  color,  as  a general 
rule,  the  more  highly  carbonized,  or  harder,  will  be  the  steel 
produced  ; at  the  same  time  both  specific  gravity  and  tenacity 
are  reduced. 

113.  Bltstee-steel. — A more  decided  peculiarity  of  the  con- 
verted bars  is  the  blistering  of  the  external  siu’face,  whence  the 
term  hlister-steel  is  derived.  When  the  blisters  are  small  and 
tolerably  regularly  distributed,  the  steel  is  of  good  quality  ; but 
when  large,  and  only  occurring  along  particular  lines,  they  may 
be  consiclered  as  indicative  of  defective  composition  or  want  of 
homogen  iety  in  the  iron  employed. 

Blister-steel  bars  are  generally  subjected  to  one  or  more 
reheatings  in  packets,  or  fagots,  and  weldings  by  hammering  or 
rolling,  whereby  the  texture,  becomes  more  uniform,  and 
strength  and  elasticity  are  increased,  but  with  a progressive 
diminution  of  hardness. 

114.  Speing-steel,  or  tilted  steel,  is  produced  by  heating 
blistered  bars  at  an  orange-red  heat,  and  drawing  them  down 
either  under  the  hammer,  or  by  rolling. 

115.  Siieae-steel  is  a better  quality  obtained  by  drawing 
out  the  original  bars,  which  are  piled  together  in  fagots,  and 


38 


NAVAL  OEDNANCE  AND  GUNNERY. 


welded.  The  product  of  this  operation  is  known  as  single 
shear. 

It  may  be  further  refined  by  doubling  the  bars,  and  repeat- 
ing the  process  of  heating  and  welding,  making  double  shear- 
steel. 

Shear-steel  breaks  with  a finer  fracture,  is  tougher,  and  capa- 
ble of  receiving  a finer  and  firmer  edge  and  a higher  polish 
than  blistered  or  spring-steel. 

116.  Cast-steel. — The  best  and  most  unlfoim  quality  of 
steel  can  only  be  obtained  by  fusion. 

That  obtained  by  cementation  is,  as  a rale,  very  unequal  in 
quality ; and  uniformity  can  oidy  be  attained  by  repeated 
fagoting  and  welding,  steps  which  are  necessarily  attended 
with  a loss  of  carbon  and  consequent  rediiction  of  hardness. 

The  requisite  uniformity  of  composition  may,  however,  be 
obtained  by  breaking  up  the  crude  bars  produced  in  the  forge 
or  by  cementation,  and  exposing  them  to  a strong  heat  in  cru- 
cibles out  of  contact  with  the  air.  The  product,  when  melted, 
is  poured  out  into  cast-iron  molds  forming  ingots  of  cast-steel, 
which  are  much  more  regular  in  composition  and  texture  than 
the  original  material. 

117.  Process  of  Maxtjfactuee. — Crucibles  of  the  most 
refractory  fire-clay,  mixed  with  plumbago,  varying  in  capacity 

from  thirty  to  fifty  and  a hun- 
dred pounds,  or  more,  in  weight, 
are  charged  with  fragments  of 
blister  or  shear-steel,  and  placed 
in  furnaces.  (Fig.  10.)  The  fur- 
naces are  furnished  with  covers, 
h,  and  a chimney,  a,  to  increase 
the  draught  of  air,  and  the  cruci- 


bles, e,  are  furnished  Avith  lids  of 
clay  to  exclude  the  air.  The  fur- 
naces containing  the  crucibles  are 
filled  with  fuel ; and  for  the  per- 
fect fusion  of  the  steel  the  most 
intense  heat  is  kept  up  for  tAvo 
or  three  hours.  Il'hen  the  steel 
is  thoroughly  melted  the  cruci- 
bles are  removed,  either  bj'  hand 
or  machinery,  and  their  contents 
poured,  in  the  liqiud  state,  into 


Fig.  10. — Furnace  and  Pot  for  melt- 
ing- Steel,  g.  Grate,  c,  Cracible. 
b,  Cover  of  Furnace,  a.  Chimnev. 


ingot-moulds  of  the  shape  and  size  required. 

118.  Steel  Ixgots. — Although  steel  may  be  east  into  ingots 
it  is  too  imperfectly  fluid  to  be  cast  into  A’ery  small  articles. 


CA2TN0N  METALS. 


39 


When  the  crucibles  are  emptied,  if  sound,  they  are  returned 
to  the  furnace  again  and  cliarged.  The  ingots  of  steel  are  taken 
to  the  forge  or  rolling-mill,  and  prepared  by  hammering  or 
rolling  into  shape  in  the  same  manner  as  other  steel,  but  with 
less  heat  and  with  more  precaution. 

The  great  secret  of  the  manufacture  is  in  the  selection  and 
mixture  of  irons,  and  in  the  pouring  of  sound  iugots. 

Large  castings  are  made  by  emptying  a sulhcient  number  of 
large  crucibles  into  an  immense  ladle  placed  over  the  mould  ; 
the  ladle  is  then  tapped  from  the  bottom. 

Great  skill  in  melting  and  pouring  the  metal,  and  particu- 
larly in  heating  and  forging  such  great  masses,  Avithout  burning 
them  on  the  outside,  cr  failing  to  condense  them  to  the  core,  is 
of  obvious  importance. 

119.  Steel,  like  iron,  is  improved  by  hammering  and  rolling ; 
consequently  Avhen  a large  cast-steel  block  is  required  of  great 
tenacity  for  a particular  purpose,  the  metal  is  not  run  into  a 
mold  of  the  shape  and  size  of  the  required  finished  dimensions, 
but  it  is  cast  into  a short,  thick  ingot,  and  then  hammered  and 
draAvn  to  the  required  finished  dimensions,  or  it  is  rolled  to  the 
reqiiired  shape  between  the  rollers. 

The  draAving  down  of  a heavy  ingot  requires  : First,  a uni- 
form he.xt  throughout  the  mass  ; and  to  soften  the  centre  of  such 
a casting  without  burning  the  outside  requires  a moderate  and 
steady  temperature  maintained  for  several  days.  Second.  The 
effect  of  the  hammer  must  be  felt  at  the  centre  of  the  mass,  in- 
stead of  being  confined  to  the  outside.  A light  blow  would  be 
absorbed  in  changing  the  figure  of  the  surface-metal,  and  in 
breaking  and  distorting  the  grain,  while  a great  Aveight  falling 
from  a moderate  height  avouIcI  be  resisted  by  the  Avhole  mass  of 
the  forging,  and  thus  felt  at  its  centre. 

The  heaviest  hammers,  however,  are  found  to  produce  too 
much  local  and  exterio]’,  and  too  little  distributed  and  interior, 
compression  upon  large  masses  of  steel;  therefore  hydraulic 
pressures  are  much  used  for  drawing  and  shaping  large  ingots. 

120.  Bessejier  Process.— This  is  one  of  the  simplest 
methods  of  jaroducing  cast-steel  in  large  quantities.  It  combines 
the  action  of  the  puddling  and  ordinary  steel-melting  furnace 
into  one  operation.  The  essence  of  the  process  consists  in  inject- 
ing large  quantities  of  air  into  a bath  of  molten  cast-iron  through 
a largo  number  of  small  orifices  situated  in  the  bottom  of  the 
converting-vessel  in  order  that  the  combustion  of  the  carbon, 
and  other  matters  in  combination,  may  take  place  rapidly  and 
uniformly. 

By  this  means  a very  high  temperature  is  developed  in  the 


40 


NAVAL  ORDNANCE  AND  GUNNERY. 


con  verting- vessel,  the  heat  being  sufficient  to  melt  the  cleear- 
honized  malleable  iron  instead  of  producing  it  in  a pasty,  welda- 
ble condition,  as  is  the  case  in  the  puddling-furnace. 


Fig.  11. — Bessemer’s  process.  A,  ConTerting-vesse].  B*,  Hood  for  carrying 
the  carbonic  oxide  gas  into  the  chimney,  B.  C,  Crane  for  swinging  t’ne 
ladle  under  the  converter. 

This  great  increase  of  temperature  is  obviously  due  to  the 
rapidity  of  combustion  owing  to  the  intimate  contact  of  the  air 
with  the  molten  metal,  instead  of  being  merely  in  contact  with 
its  surface  as  in  puddling. 

121.  To  PuoDUCE Bessemee Steel. — Steel  maybe  produced 
by  this  process  by  interrupting  the  blowing  after  partial  decar- 
bonization  of  the  charge,  the  proper  moment  for  stopping  the 
operation  being  determined  by  the  time  employed  and  the 
appearance  of  the  flame  issuing  from  the  mouth  of  the  convert- 
ing-vessel ; or  the  metal  may  be  completelj"  decarbonized,  and 
then  brought  back  to  the  composition  of  steel  by  the  addition 
of  highly  carbonized  melted  pig-iron,  in  sufficient  quantity  to 
restore  the  necessary  amount  of  carbon. 

122.  The  Conveetek,  or  furnace,  consists  of  an  egg  or  pear 
shaped  vessel  suspended  upon  trunnions,  and  provided  Avith 
appropriate  moving  mechanism,  whereby  it  may  be  rotated  ver- 
tically through  an  angle  of  about  180°.  The  outer  casing,  or 
shell,  is  made  of  wrought-iron  plates  riveted  together,  the  inte- 
rior lining  of  the  most  refractory  material  obtainable. 

The  Trunnions. — The  suspension  is  effected  by  means  of  a 
stout  hoop  of  Avrought-irou  shrunk  on  to  the  body  of  the  con- 


CANNON  METALS. 


41 


verier,  and  carrying  two  trunnions,  wiiicli  run  in  bearings  sup- 
ported by  cast-iron  standards. 

One  of  these  trunnions  is  solid,  while  the  other  is  hollow, 
forming  a passage  for  the  blast.  (Fig.  12.) 

The  Twyer-hox. — 

The  bottom  of  the 
converter  is  flat,  and 
contains  the  twyer- 
lox,  E,  which  is  a 
cylindrical  chamber, 
connected  by  a curved 
pipe  with  the  hollow 
trunnion. 

The  Twyers  are 
cylindrical,  or  slightly 
tapered,  fire-bricks,  C, 
each  perforated  by 
seven  parallel  holes, 
about  half  an  inch 
in  diameter.  Usually 
five  to  seven  of  these 
bricks  are  used,  which 
are  arranged  vertical- 
ly, and  at  equal  dis- 
tances apart  in  the 
lining  of  the  bottom 
of  the  converter,  their 
lower  ends  communicating  with  the  twyer-box. 

123.  Chargestg  the  Conveetee. — The  charge  of  pig-iron, 
which  may  be  of  any  weight  from  one  to  ten  tons,  or  more, 
according  to  the  size  of  the  vessel,  is  melted  in  a reverberatory 
or  other  furnace.  The  converter  is  turned  to  a horizontal  posi- 
tion (Fig.  11),  to  receive  the  charge  of  molten  metal,  which  is 
run  in  through  a movable  gutter  of  wrought-iron  lined  with  sand. 

124.  The  Blast. — After  the  converter  is  charged  the  blast 


Fig.  12. — Bessemer’s  steel  converter. 

A.  Transverse  section  through,  trunnions. 

B.  Bottom  plan. 

C.  Section  of  twyer  brick.  D.  Plan  of  ditto. 


must  be  admitted  before  it  is  turned  back  to  the  vertical  posi- 
tion, otherwise  the  molten  metal  would  run  down  through  the 
twyers. 

A pressure  of  from  five  to  six  pounds  per  square  inch  is 
required  to  overcome  the  hj’draulic  head  of  the  liquid  column 
of  metal,  and  from  nine  to  foui'teeu  pounds  more  to  force  the 
air  through  at  the  proper  velocity,  or  from  fifteen  to  twenty 
pounds  per  square  inch  total  pressure. 

After  the  blast  is  turned  on  the  converter  is  slowly  brought 
back  to  the  vertical  position. 


42 


NAVAL  ORDNANCE  AND  GUNNERY. 


125.  Pkocess  of  Conveesion. — During  tiiis  period,  lasting 
from  four  to  six  minutes,  tire  action  going  on  is  similar  to  that 
in  the  refinery  in  the  first  stage  of  puddling— the  conversion 
of  graphite  into  combined  carbon,  and  the  oxjdation  of  silicon 
with  the  formation  of  a silicate  of  iron  and  manganese. 

In  the  second  or  boiling  period,  when  the  ox^^gen  of  the 
blast  begins  to  attack  the  carbon,  the  action  becomes  veiy  vio- 
lent, and  the  flame  increases  in  brilliancy.  This  lasts  for  about 
six  or  eight  minutes  longer. 

In  some'  establishments  the  process  is  stopped  here,  the 
recpiired  decarhonization  being  determined  by  the  time  of  its 
duration,  and  by  the  color  of  the  flaines;  but  a far  more  exact 
method  of  ascertaining  when  the  requisite  amount  of  carbon 
has  been  removed,  consists  in  viewing  the  flame  through  the 
spectrosGOjye,  which  enables  the  observer  to  detect  a certain  lino 
in  the  spectrum  or  image  of  the  flame,  the  disappearance  of 
which  marks,  to  within  a few  seconds,  the  conclusion  of  the 
process.  In  others  it  is  continued  until  from  the  sudden  drop- 
ping of  the  flame,  the  iron  is  known  to  he  quite  decarbonized. 
When  the  converter  is  turned  hack  to  the  horizontal  position,  and 
the  proper  quantity  of  molten  pig-iron  of  known  quality  is  run  in. 

12G.  Casting  the  Ingots. — The  vessel  is  turned  on  its  trun- 
nions until  the  fluid  steel  will  run  out  into  the  casting-ladle 
(Fig.  11),  which  is  attached  to  the  arm  of  a hydraulic  crane,  C, 
so  as  to  be  brought  readily  over  the  molds. 

The  ladle  is  provided  with  a fire-clay  plug  at  the  bottom, 
the  raising  of  which  by  means  of  a suitable  lever,  allows  the 
fluid  steel  to  descend  in  a clear  vertical  stream  into  the  molds. 

As  soon  as  the  fix’st  mold  is 
filled  the  plug-valve  is  depressed, 
and  the  metal  prevented  from  flow- 
ing until  the  casting-ladle  is  moved 
over  the  next  mold.  To  pour  a 
heavy  ingot  several  converting  ves- 
sels are  emptied  into  one  mold. 

The  molds  usually  employed 
are  made  of  cast-iron,  and  arranged 
in  a semicircle  on  the  floor  of  the 
casting-pit. 

127.  Hammering  the  Ingots  — 
When  drawn  from  the  molds  the 
ingots,  like  those  obtained  from 
steel  melted  in  crucibles,  are  always 
more  or  less  unsound,  and  require  to  he  compacted  by  hammer- 
ing after  reheating.  If  this  is  done  before  the  interior  has 


Fig.  13. 


CAXNOX  METALS. 


43 


solidified  mneli  fuel  is  saved,  and  the  core  is  certain  to  be 
thoroughly  heated. 

128.  Another  and  more  recent  Form  of  Converter^  suggested 
by  Bessemer,  shown  in 
Figs.  13  and  14,  has  a 
globular  form,  and  is 
seven  feet  in  diameter, 
the  air-blast  introduced 
through  a single  twyer 
passed  through  the  top 
of  the  converter,  and 
made  of  circular  fire- 
bricks, D (Fig.  14), 
strengthened  by  a stout 
iron  rod  passing  down 
the  centre,  and  terminat- 
ing in  a kind  of  rosette 
with  numerous  apertures, 
through  which  the  air  is 
projected  into  the  liquid 
iron. 

When  the  conversion 
is  finished  the  twyer  is  lifted  out  by  an  ingenious  hydraulic 
ci’ane,  E,  and  the  converter  tipped  by  the  action  of  a hydraulic 
ram  in  order  to  discharge  its  contents  into  the  casting-ladle. 

In  the  Bessemer  methods,  and  in  others,  air  passes  tlirough 
iron,  thus  endowing  the  latter  with  the  carbon,  whose  addition 
makes  the  difference  between  iron  and  steel.  A greater  or  less 
proportion  of  this  air  remains  in  the  substance,  and  occasions 
holes  and  flaws.  These,  of  course,  weaken  the  steel,  and  make 
it  liable  to  break  up. 

129.  WniTWOETH  Metal. — In  order  to  procure  a more 
dense  metal  than  forged  steel,  Whitworth  has  resorted  to  the 
expedient  of  compressing  the  steel  while  in  a liquid  state.  He 
has  applied  a pressure  of  twenty-five  tons  to  the  square  inch, 
hut  estimates  that  eight  tons  are  sufficient  to  expel  air-bubbles, 
and  that  then,  reheating  the  ingot,  the  metal  may  be  com- 
pressed by  hammering,  thus  producing  a resulting  metal  which 
may  be  regarded  with  certainty  as  free  from  air-cells,  and  as 
superior  to  all  other  steels. 

130.  Annealing  is  a process  applied  to  the  manufacture  of 
metals  to  prevent  the  particles  arranging  themselves  in  that  con- 
dition which  produces  a brittle  quality. 

The  texture  of  a metal  depends  grea^tly  upon  whether  it  has 
been  gradually  or  suddenly  cooled ; and  this  influences  many  of 


Fig.  14. — Section  of  Bessemer’s  globular 
Converting-vessel.  A,  The  converter.  B, 
Pulley  ■wheel  for  tipping  the  converter, 
connected  by  a 'wire  rope  with  a hydraulic 
ram.  G,  Pipe  conveying  the  blast.  H, 
Elbow-pipe  with  telescopic  joint. 


44: 


NAVAL  ORDNANCE  AND  GUNNERY. 


its  most  important  mechanical  properties : as,  for  instance,  its 
hardness  or  brittleness,  or  its  softness  and  malleability.  The 
former  qualities  are  given  by  cooling  it  rapidly,  the  latter  by 
cooling  it  slowly. 

When  cast-iron  has,  by  too  rapid  cooling,  acquired  the  quality 
of  liardness,  it  may  in  some  degree  be  taken  from  it  again  by 
heating  it  a second  time  and  cooling  it  gradually.  This  process 
is  called  annealing. 

Steel  is  most  hardened  when  it  is  raised  to  the  highest  tem- 
perature which  it  can  receive,  and  then  suddenly  cooled  by  being 
plunged  in  mercairy  or  an  acid,  or  into  a mass  of  lead  ; if  in- 
stead of  these  substances,  water  or  oil  be  used  to  cool  it,  the  tem- 
per obtained  is  not  so  hard. 

131.  Corresponding  to  every  different  degree  of  heat  to 
which  the  metal  is  raised,  there  is  a different  hardness,  but  as 
these  are  all  different  degi’ees  of  red  heat,  which  it  is  very  diffi- 
cult to  distinguish  from  one  another,  it  is  customary  to  make 
use  of  a remarkable  property  by  which  the  metal  can  be  made 
to  lose  to  any  degree,  the  hardening  which  it  has  acquired,  by 
heating  it  again  to  an  inferior  degree  and  allowing  it  to  cool 
grachrally.  This  is  the  process  called  tempering.^  commimicating 
in  the  first  place  to  the  steel  a hardness  above  that  required, 
then  heating  it  again  over  charcoal  and  cooling  it  gradaially. 

This  process  is  facilitated  by  certain  remarkable  changes  of 
color  which  appear  in  the  steel  as  it  undergoes  the  second  heat- 
ing. These  colors  are:  straw-color,  yellow, purple,  red, 'ciolet- 
l)lue,  l)lue,  and  clear-watery-hlue,  and  they  indicate  the  point  at 
which  the  second  heating  should  be  arrested  to  obtain  the  tem- 
per or  degree  of  hardness  required  for  different  purposes. 

132.  Tempering  Steel  in  Oil. — Oil  is  used  as  a bath  for 
toughening  large  tubes  of  mild  cast-steel,  calculated  to  be  used 
as  barrels  for  heavy  built-up-guns,  because  of  the  high  tempera- 
ture required  to  convert  it  to  the  vaporous  state,  and  its  imper- 
fect conducting  quality,  whicli  causes  the  steel  to  part  with  its 
heat  slowly.  This  slow  rate  of  cooling  is  necessary  to  form  a 
uniform  degree  of  contraction,  thus  giving  the  steel  a longer 
time  for  the  re-arrangement  of  its  particles  and  making  the  strain 
more  uniform  throughout  the  mass.  Heavy  masses  or  thick 
lumps  of  highly  carbonized  steel,  whether  tempered  in  oil  or 
water,  cannot  be  hardened  without  becoming  fractured  either 
internally  or  externally. 

The  process. — A tube  of  mild  cast-steel  is  lifted  by  a power- 
ful crane  and  placed  in  a perpendicular  position  in  an  upi-ight 
furnace,  which  has  been  previously  heated  with  wool  to  a 
red-heat.  It  rests  on  an  iron-shoe  placed  on  the  grate-bars  to 


CAlS'NOX  JIBTALS. 


45 


prevent  tlie  cold  air  from  coming  in  contact  with  its  extreme 
end. 

Great  care  is  taken  to  heat  the  mass  xiniformlv,  fuel  being 
added  gradually  until  the  whole  tube  is  entirely  suiTounded  with 
wood,  thrown  in  at  tlie  top  of  the  furnace. 

Wood  is  used  because  of  its  purity ; it  is  not  so  liable  to 
degrade  the  steel  as  other  fuels. 

The  amount  of  heat  received  by  the  steel  is  judged  by  eye 
and  by  long  practice  and  attention.  The  more  uniform  the 
temperature,  the  straighter  the  block  will  keep,  and  the  more 
even  its  temper.  After  the  steel  has  accpiired  the  proper  uni- 
form temperature  throughout,  the  travelling  crane  is  brought 
over  the  furnace,  its  top  removed,  and  the  large  iron  tongs, 
pendant  from  the  ci’ane,  fasten  themselves  to  the  steel  tube  ; a 
small  collar  being  upon  its  end  to  prevent  the  tongs  slipping. 

The  Oil-hath. — The  tube  of  steel  is  now  drawn  out  of  the 
furnace  and  sunk  into  a large  iron  tank  about  twenty  feet  deep, 
containing  several  hundred  gallons  of  oil.  The  heated  steel  in 
passing  into  the  oil  will  sometimes  cause  the  surface-oil  to  take 
tire,  which  is  extinguished  by  closing  the  top  of  the  tank. 

A covering  of  coal  is  also  formed  round  the  steel  by  the 
burned  oil,  which  greatly  retards  transmission  of  heat. 

Tlie  tank  has  a Avater-space  surrounding  it,  and  as  the  steel 
parts  with  its  heat,  raising  the  temperature  of  the  oil,  the  tem- 
perature of  the  Avater  is  also  raised.  The  water,  as  it  is  heated, 
is  drawn  off  by  an  escape-pipe,  and  a supply  of  cold  Avater  is 
continually  running  in,  thus  the  heat  is  gradually  taken  from 
the  mass.  Exceeding  toughness  is  the  result  of  the  operation  ; 
the  tensile  strength  of  the  steel  is  made  higher,  and  it  is  harder 
and  more  elastic. 


Section  Y. — Bronze. 

133.  Bkonze  foe  CANNOiSr,  consists  of  ninety  parts  of  pure 
copper  and  ten  parts  of  tin,  allowing  a variation  of  one  part  of 
tin,  more  or  less.  ’When  the  mixture  is  well  made  the  metal  is 
homogeneous ; the  fracture  is  of  a uniform  yellow  color  with 
an  even  grain.  The  specific  gravity  of  bronze  is  about  8.T50, 
being  greater  than  the  mean  of  the  specific  gravities  of  copper 
and  tin. 

134.  Pure  copjper  is  of  a red  color,  inclining  to  yellow;  it 
has  a fine  metallic  lustre.  The  fracture  of  cast-copper  is  even 
grained ; that  of  the  forged  bar  exhibits  a short,  even,  close 
grain  of  a silky  appearance,  it  is  strong,  very  ductile,  and  very 


46 


NAVAL  ORDNANCE  AND  GUNNERY. 


malleable.  Tlie  greater  the  purity  of  the  copper,  the  more 
malleable  it  is  and  the  finer  the  grain.  Its  specific  gravity  varies 
from  8.600  to  9.000. 

The  copper  of  commerce  is  impure,  frequently  containing 
oxygen,  silicon,  iron,  lead,  tin,  zinc,  antimony,  and  arsenic.  It 
should  he  rejected  for  the  manufacture  of  guns,  if  it  contains 
sulphur  in  an  appreciable  degree,  more  than  one-thousandth  of 
ansenic  and  antimony  united,  more  than  about  three-thousandths 
of  lead,  iron,  or  oxygen,  or  five-thousandths  of  other  substances 
all  together. 

135.  Pure  Tin  is  of  a white  color,  a little  darker  than  sil- 
ver ; it  is  very  malleable  and  susceptible  of  being  rolled  into 
thin  sheets  ; it  is  not  very  ductile ; it  is  soft,  and  when  in  rods  or 
bars  it  is  bent  backwards  and  forwards  gives  a peculiar  crack- 
ling sound,  the  distinctness  of  which  is  in  proportion  to  the 
purity  of  the  tin.  Its  specific  gravity  is  from  7.290  to  7.320. 
Tin  for  gun  metal  should  be  rejected  if,  when  run  into  drops,  it 
has  not  a smooth  and  reflecting  surface,  without  any  consider- 
able sign  of  rough  spots ; if  when  analyzed  it  contains  one- 
thousandth  of  arsenic  and  antimony  united,  three-thousandths 
of  lead  or  iron,  or  four-thousandths  of  foreign  substances. 

All  bronze  ought  to  be  rejected  which  contains  sulphur  in 
an  appreciable  amount,  .001  arsenic  and  antimony,  .003  lead, 
iron,  or  zinc,  or  in  all  more  than  .005  of  foreign  substances. 

The  fracture  of  bronze  may  give  indications  sufficient  to 
authorize  the  rejection  of  certain  bronzes  full  of  sulphur  or 
oxydes. 

136.  Management  of  Bronze. — The  circumstances  of  chief 
difficulty  and  importance  in  the  manipulation  of  bronze,  as 
affecting  the  production  of  cannon,  are: — * 

First.  The  chemical  constitution  of  the  alloy  as  influencing 
the  balance  of  its  hardness  and  tenacity. 

Second.  Its  chemical  constitution  and  what  other  conditions 
influence  the  segregation  of  the  cooling  mass  of  the  gun,  when 
cast,  into  two  or  more  alloy’s  of  different  and  often  variable  con- 
stitutions. 

Third.  The  effect  of  rapid  and  of  slow  cooling,  and  of  the 
temperature  at  which  the  metal  is  fused  and  poured. 

Fourth.  The  effects  due  to  repeated  fusions  and  to  foreign 
constituents  in  minute  proportions  entering  into  the  alloy. 

In  bronze,  as  in  every  other  material  for  cannon,  while  suffi- 
cient hardness  must  be  secured  to  resist  longest  the  abrasion  of 
projectiles,  and  the  deflagration  of  the  powder  along  with  the 


* MaRet. 


CANNON  METALS. 


47 


greatest  ultimate  tenacity,  there  must  be  a certain  rigidity  and 
ductility,  with  ultimate  cohesion. 

The  hardness  and  rigidity  increase  with  the  proportion  of 
tin ; the  ductility  and  tenacity  with  that  of  copper,  hut  not  hr 
any  direct  ratio  in  either  ease.  _ The  specific  gravity  increases 
with  the  copper.  The  fusibility  is  always  greater  than  that  of 
copper,  and  less  than  that  of  tin.  The  ultimate  cohesion  is 
always  less  than  that  of  tough  copper,  hut  greater  than  that  of 
tin.  The  ductility  less  than  that  of  copper  and  greater  than 
that  of  tin.  The  hardness  is  always  greater  than  that  of 
either. 

137.  In  common  with  the  great  majority  of  metallic  alloys, 
bronze  is  held  so  loosely  in  combination,  that  very  slight  forces 
are  sufiicient  to  induce  its  segregation  into  two  or  more  different 
alloys,  which  on  cooling  are  found  to  occupy  different  portions 
of  the  mass. 

Thus,  in  a gun  cast  vertically,  the  external  portions  which 
cool  first  have  a determinate  constitution  difierent  from  that 
assigned  by  the  proportions  of  the  metals,  as  fixed  foT  fusion. 
The  interior  of  the  gun  which  cools  last  has  another  constitu- 
tion different  from  either,  and  always  richer  in  tin.  But  when 
the  whole  gun  has  become  solid,  and  portions  are  examined 
from  the  extreme  lowest,  middle,  and  highest  parts  of  the  pre- 
viously fluid  column  of  metal,  it  is  found  that  these  again  differ 
from  each  other,  and  that  this  difference  varies,  in  the  vertical 
or  exterior,  or  crust  alloy,  which  has  cooled  first,  and  for  the 
interior  column  of  alloy  that  has  cooled  last ; so  that,  in  fact  of 
any  gun,  no  two  adjacent  portions  have  strictly  the  same  chemi- 
cal constitution  ; the  maximum  of  copper  being  found  in  the 
exterior  and  hi’eeeh  of  the  gun,  and  the  maximum  of  tin  in  the 
interior  and  highest  part  of  the  metallic  column. 

138.  The  constitution  of  the  alloy  changes,  not  only  in  cool- 
ing, hut  in  melting  by  oxydation ; resulting  in  the  continual 
reduction  of  the  quantitj^  of  tin,  which  oxydizes  much  faster 
than  copper,  though  the  latter  he  present  in  so  much  greater 
mass.  The  oftener  the  alloys  are  melted  the  more  difficult  it  is 
to  produce  solid  eastings  with  them. 

139.  The  difficulty  of  making  sound  castings  from  old  and 
often  remelted  alloys,  arises  from  oxydation,  which  in  bronze 
takes  place  in  such  proportions  that  for  one  part  by  weight  of 
tin  oxydized,  there  are  from  three  to  four  of  copper.  A part  of 
this  oxygen  is  absorbed  or  combined  and  given  up  again  by  one 
or  both  metals,  at  the  moment  of  consolidation,  and  its  evolution 
causes  the  dissemination  of  minute  air-vesicles  through  the  mass 
which  is  the  cause  of  imperfect  eastings. 


48 


NAVAL  ORDNANCE  AND  GUNNERY. 


These  are  seldom  known  to  occur  in  suck  abundance  in  new, 
or  not  frequently,  fused  metals. 

140.  In  consequence  of  the  difference  in  the  fusibility  of 
tin  and  copper,  the  perfection  of  the  alloy  depends  much  on 
the  nature  of  the  furnace  and  the  treatment  of  the  melted 
metal.  By  these  means  alone,  the  tenacity  of  bronze  has  been 
carried  at  the  Washington  Havy  Yard  Foundry,  as  high  as 
60,000  lbs. 

141.  Other  Alloys. — For  many  years  experiments  have 
been  made  for  the  improvement  of  alloys  used  in  the  fabrica- 
tion of  cannon,  and  trials  have  been  instituted  to  ascertain 
the  modilications  produced  in  the  resistance  of  bronze  for 
cannon,  by  different  compositions  and  various  modes  of  manu- 
facture.* 

142.  Phosphorus  Bronze. — By  the  addition  of  about  two 
per  cent,  of  phosphorus  to  ordinary  bronze,  and  casting  tlie 
metal  in  ingot-molds  for  the  purpose  of  rapid  cooling,  a metal 
has  been  attained  having  a hardness  approaching  that  of  steel ; 
an  elastic  and  absolute  resistance  varying  between  sixty  and 
175  per  cent,  above  ordinary  bronze,  a composition  more  homo- 
geneous than  that  of  bronze,  and  consequently  resisting  better 
the  effects  of  the  combustion  of  gim  powder. 

143.  It  is  thought  by  some  that  the  best  gun  will  eventually 
be  constructed  Avith  some  extremely  dense  and  homogeneous 
alloy,  cast  and  used  withoiit  being  drawn  under  the  hammer. 

144.  If  a gun  is  made  of  an  alloy  possessing  great  density, 
the  detonating  force  of  the  powder  will  be  resisted  by  a greater 
quantity  of  the  metal  employed,  than  it  can  be  by  making  use 
of  one  with  greater  elasticity. 

145.  Yo  theoretical  trials  of  any  extent,  specially  designed 
to  ascertain  the  truth  concerning  this  point,  have  ever  been 
made;  and  it  is  impossible,  in  the  absence  of  further  experi- 
ments, to  predict  either  great  success  or  failure  for  the  alloys. 

Although  the  alloying  of  copper,  especially  for  cannon,  has 
been  practised  for  more  than  five  hundred  years,  it  is  yet  much 
undeveloped. 

146.  While  certain  alloys  of  both  iron  and  copper  haA'e  one 
important  feature  in  common  hemogeneity,  due  to  fusibility  at 
practicable  temperatures,  the  alloys  of  iron  have  this  grand 
advantage,  iron  is  everyAvhere  cheap  and  abundant ; and  the 
other  necessary  ingredients  and  fluxes — carbon,  manganese, 

* Essay  on  the  use  of  various  Alloys,  especially  of  Phosphorus  Bronze,  for 
the  Pounding  of  G innon.  By  C.  Montefiore-Levy,  and  C.  Kunliel.  Brussels, 
1870.  Translated  by  John  D.  Brandt,  Navy  Dapartment,  Ordnance  Bureau. 
Washington  : Government  Printiug  Office,  1873. 


CANNOIT  METALS. 


49 


zinc,  and  silicium — are  equally  abundant,  and,  in  some  locali- 
ties, already  mixed,  although  perhaps  not  in  the  proper  pro- 
portions. 


Section  YI. — General  Qualities. 

147.  Eequieements.- — The  qualities  necessary  in  cannon- 
metals,  are : strength  to  resist  the  explosion,  weight  to  overcome 
the  severe  recoil,  and  hardjiess  to  endure  the  wear  in  the  bore. 

148.  The  selection  of  a suitable  material  is  a very  import- 
ant consideration  in  the  construction  of  cannon,  in  consequence 
of  the  difliculty  of  obtaining  any  ore  that  possesses  all  the 
qualities  required  of  it. 

149.  Peopeeties  of  IIetals. — It  is  necessary  to  a clear 
understanding  of  the  subject,  briefly  to  consider  the  various 
properties  of  metals  which  afiect  their  value  for  cannon  con- 
struction. 

150.  Dexsitt  is  a term  used  synonymously  with  specific 
gravity,  to  denote  the  quantity  of  matter  which  a body  contains 
under  a given  or  determinate  surface  ; for  example,  a cubic  foot. 

The  quantity  of  matter  in  any  body  is  called  its  mass,  and 
is  measured  by  the  Aveight  of  the  body  to  which  it  is  always 
proportioned.  Hence,  the  density  of  any  body  is  great  in  pro- 
portion as  its  Aveight  is  great  and  its  volume  small ; or  the  den- 
sity of  bodies  is  directly  as  their  mass,  and  inversely  as  their 
volume.  It  follows  also  from  the  definition,  that  if  tAvo  bodies 
have  the  same  A'olume,  their  densities  are  directly  as  their 
masses,  or  Aveights ; and,  that  if  tAvo  bodies  haAm  the  same  mass, 
or  weight,  their  densities  are  respectively  in  the  inverse  ratio  of 
their  volumes. 

151.  Haedxess  is  the  condition  of  the  force  of  cohesion  in 
solids,  AAdiich  enables  their  constituent  particles  to  retain  their 
relati\'e  position  and  resist  any  physical  force  Avhieh  tends  to 
alter  the  figure  of  the  body.  Hardness  is  entirely  different 
from  density,  for  although  gold  is  denser  than  glass,  yet  glass 
is  harder  than  gold.  Iron  is  lighter  but  harder  than  gold. 

Some  metals  are  reudei'ed  hard  with  great  readiness.  This 
is  of  inestimable  value  in  the  manufacture  of  steel,  Avhich  can 
be  varied  in  hardness  by  heating,  suddenly  cooling,  and  then 
tempering.  Hardness  is  often  accompanied  by  brittleness;  but 
this  can  be  generally  overcome  by  heating  and  slow  ccmling ; 
this  process,  however,  often  takes  aAvay  from  the  hardness. 

In  the  production  of  alloys  this  useful  property  is  frequently 
developed ; copper  and  tin,  neither  of  Avhich  are  remarkable  for 
4 


50 


NAVAL  ORDNANCE  AND  GUNNERY. 


liardness,  possess  this  quality  when  combined.  Without  a cer- 
tain degree  of  hardness,  the  shape  of  the  bore  in  cannon  will 
he  rapidly  altered  by  the  action  of  the  projectile,  and  the  gases 
resulting  from  the  combustion  of  the  charge. 

152.  Beittleness  is  a property  of  bodies  which,  although 
solid,  yet  are  so  weakly  hound  together  that  a very  small  me- 
chanical force  suffices  to  separate  their  particles. 

153.  Tenacity  is  that  quality  of  bodies  which  keeps  them 
from  parting  without  considerable  force. 

15-1.  Tensile  Stkength,  is  the  degree  of  stretching  which  a 
body  can  endure  by  dravvdng  it  in  the  direction  of  its  length. 

155.  PoiiOSiTY. — All  bodies  liave  between  the  elementary 
particles,  or  atoms,  interstices  through  which  heat  penetrates 
into  them,  and  into  some  of  them  air,  water,  and  other  fluids. 
These  last  are  said  to  he  'porous. 

That  metals  are  porous  has  often  been  proved  by  submitting 
metallic  vessels  containing  water  to  great  pressure,  by  which  the 
water  was  made  to  weep  through  the  pores  in  the  surface.  That 
all  metals  are  more  or  less  porous  sufficiently  accounts  for  the 
fact  that  they  are  also  more  or  less  compressible. 

156.  Elasticity  is  the  inherent  property  of  certain  bodies 
by  which  they  recover  their  former  figure,  or  state,  after  exter- 
nal pressure,  tension,  or  distortion. 

The  force  with  which  metals,  when  extended  or  compressed, 
tend  to  recover  their  form,  that  is,  the  force  necessary  to  keep 
them  extended,  or  compressed,  is  proportional  to  the  amoimt  of 
the  extension,  or  compression,  they  have  received. 

The  property  of  the  elasticity  of  metals  is  of  the  greatest 
moment  in  connection  with  their  use  in  gun  construction,  as 
they  are  subjected  to  various  degrees  of  pressure,  and  it  becomes 
a matter  of  importance  to  know  how  far  they  will  lengthen 
themselves  under  a given  thrust  / also,  how  far  these  may  he 
carried  without  rupture. 

A bar  of  metal  is  said  to  suffer  a strain  when  the  forces 
which  act  upon  it  tend  to  lengthen  it,  and  a thrust  when  they 
tend  to  compress  it. 

All  metals  used  for  cannon  have  an  appreciable  elasticity, 
hut  the  range  of  this  elasticity,  that  is,  the  extent  to  which  they 
may  be  elongated  by  pressure,  before  permanently  changing 
their  tigure,  is  very  diverse  for  diifereut  metals,  and  very  indefl- 
nitely  determined  for  all. 

The  use  of  elasticity  is,  that  it  allows  space  for  the  power  to 
act  in  without  permanently  stretching,  and  thus  injuring  the 
metal.  Upon  application  of  an}"  force,  metal  having  no  elas- 
ticity would  either  permanently  stretch,  or  instantly  break. 


CANNON  METALS. 


51 


157.  Limit  of  Elasticity. — The  displacement  of  the  parti- 
cles of  a body  must  be  confined  within  certain  infinitely  minute 
limits,  in  order  that  they  may  return  to  the  position  they  before 
occupied  in  it.  If  those  limits  be  passed,  the  displaced  particle 
may  be  wholly  separated  from  the  rest  of  the  body  in  the 
direction  from  which  it  has  been  moved,  and  thus  a partial  rup- 
ture may  take  place ; or  other  particles  of  the  body  occupying 
the  space  which  it  has  left,  and  through  which  it  has  moved,  it 
may  take  up  its  position  under  a new  arrangement  of  particles 
exactly  as  it  did  under  the  preceding,  and  enter  into  precisely  the 
same  relation  with  them  as  before ; so  that  in  every  respect,  the 
qualities  of  the  body  shall  remain  unaltered  under  this  new 
arrangement  of  its  particles. 

158.  Pekmanent  Set. — In  this  last  case  it  is  said  to  have 
taken  a set.,  and  the  phenomenon  described  under  this  name 
includes  all  that  we  understand  by  ductility  and  malleability, 
which  terms  but  imply  different  ways  in  which  the  same  pro- 
perty of  taking  a set,  is  called  into  operation. 

Experiments  prove  that  the  elasticity  of  the  body  is  not  in- 
jured when  a set  is  given  to  it.  When  beams  of  iron  are  so 
loaded  in  the  middle  as  to  cause  them  to  take  a permanent  de- 
flection, or  set,  their  elasticity  is  found  to  be  unimpaired  by  it ; 
so  that  when  again  loaded,  they  tend  to  recover  themselves  with 
forces  Avhich  are,  as  before,  proportional  to  the  deflection. 

While  some  portions  of  the  substance  of  a metallic  body 
are  made  to  take  a set,  others  may  be  ruptured.  Its  elasticity 
may  still  remain,  but  its  extensibility  will  be  greater,  and  its 
strength  impaired. 

159.  Elasticity  oe  Toesion. — If  a wire  be  twisted  it  will 
tend  to  recover  its  natural  state  with  a certain  force,  which  is 
called  its  elasticity  of  torsion.  The  law  of  this  force  is  that  it 
is  always  proportional  to  the  angle  through  which  the  body  has 
been  twisted.  While  a piece  of  wire  of  small  diameter  may 
be  in  a degree  homogeneous,  this  quality  is  not  to  be  expected 
in  a bar,  therefore,  the  conditions  of  torsion  in  a bar  become 
complicated  and  anomalous. 

ICO.  Malleability. — The  surface  of  a body  always  yields 
to  an  impact,  however  slight. 

If  a metallic  surface  thus  yields  beyond  the  limits  of  elas- 
ticity, it  takes  a set. 

This  property,  by  which  a set  is  given  to  metals  by  impact, 
is  called  malleability. 

There  are  certain  metals,  and  certain  states  of  the  same 
metals,  in  which  this  property  of  malleability  exists  in  a greater 
degree  than  in  others.  Thus,  for  instance,  cast-iron  is  not  per- 


62 


NAVAL  ORDNANCE  AND  GUNNERY. 


ceptibly  malleable  except  in  a slight  degree,  when  OMnealed  it 
flies  in  pieces  under  the  hammer ; but  when  converted  into 
wronght-iron  it  becomes  perfectly  malleable. 

1(51.  Ductility  is  the  power  possessed  by  certain  bodies, 
and  especially  by  the  metals,  in  virtue  of  which  they  are  capa- 
ble of  beinii:  drawn  out  in  length  while  their  diameter  is  di- 
minished  without  fracture,  or  separation.  Among  the  metals 
it  may  be  called  the  property  of  being  drawn  out  into  wires. 

The  order  of  the  metals  which  are  ductile  is  almost  similar 
to  the  order  of  those  which  are  malleable. 

The  ductility  of  metals  is  most  effectually  called  into  opera- 
tion by  rolling  them.  It  is  thus  that  iron  plates  and  bars  are 
made.  Some  metals,  and  especially  soft  wronght-iron,  may  be 
considerably  and  permanently  stretched  without  rupture.  After 
stretching  they  appear  to  assume  a new  arrangement  of  particles 
and  a new  limit  of  elasticity,  until  close  to  the  point  of  rupture. 
Wrought-iroii  increases  in  tenacity  when  drawn  into  bars,  or 
wire,  or  rolled  into  plates.  Such  parts  as  have  been  so  reduced 
have  a greater  tenacity  per  square  inch,  than  when  in  the  pre- 
vious named  condition. 

162.  Ruptuee. — When  the  parts  of  a body  are  by  any  ex- 
ternal cause  separated  beyond  the  limits  of  ductility,  the  separa- 
tion becomes  permanent,  and  if  it  extend  far  enough,  this  sep- 
aration constitutes  a rupture  of  the  mass.  The  rupture  of  a 
bar  of  metal  may  take  place  either  by  a strain,  or  tension,  in 
the  direction  of  its  length,  to  which  is  ojiposed  its  tenacity  ; or 
by  a thrust  or  compressing  force  in  the  direction  of  its  lenglb, 
to  which  is  opposecl  its  power  of  resistance  to  the  crusliiny  of 
its  material,  or  each  of  these  powers  of  resistance  may  oppose 
themselves  to  its  rupture ; the  one  being  called  into  operation 
on  one  side  of  it,  and  the  other  on  the  other  side,  as  m the  case  of 
transverse  strain  / or,  lastly,  the  bar  may  be  ruptured  by  torsion. 

1G3.  Tables  of  Stkexgtii  of  Materials. — It  is  important 
to  know  to  which  of  these  forces  a material  will  first  yield,  and 
in  what  proportion  it  will  yield  differently  to  these  causes  of 
rupture. 

Tables  are  prepared  from  experiments  with  the  forces  re- 
duced to  the  square  inch,  which  are  necessary  to  tear  asunder 
the  materials  eiiumerated,  and  to  crush  them.'-^ 

IGd.  Qualities  or  CAST-lRox.f — Comparative  Strenyth. — 
The  chief  argument  against  cast-iron  as  a material  for  an  entire 
gun,  made  wnthout  regulated  initial  tension,  is  its  comparative 
weakness.  Cast-iron,  having  a tensile  strength  of  nearly 

I 


* Barlow’s  Strength  of  Materials. 


t HoUey. 


CANNON  JEETALS. 


53 


50,000  pounds  per  square  inch,  has  been  applied  to  cannon  found- 
ing. Assuming  a sufficient  supply  of  such  iron  of  uniform 
quality,  and  that  its  contraction  when  cooling  and  its  elastic 
limit  are  favorable  for  cannon  making,  it  is  still  a weak  material 
when  compared  with  steel  at  100,000  to  150,000  pounds — twice 
to  three  times  as  much.  But  cast-iron  does  not  average  50,000, 
nor  even  40,000  pounds  tensile  strength.  The  average  of  the 
highest  quality  is  not  over  about  30,000  pounds,  and  this  is 
considerably  above  the  strength  of  the  greater  proportion  of 
the  cast-iron  of  commerce. 

It  is  further  proved  that  the  strongest  iron  does  not  always 
make  the  most  enduring  gun.  Several  experiments  mentioned 
by  Captain  KodmaiV^  illustrate  the  general  experience  in  this 
direction. 

This  infei’iority  of  the  strongest  iron  for  guns  is  attributed 
to  its  greater  contraction  in  cooling  ; and  in  the  examples  cited, 
the  best  guns  were  stated  to  have  been  made  of  low,  soft,  gray 
iron  of  moderate  tenacity  and  small  shrinkage ; while  the 
poorest  were  made  of  high,  hard,  close-grained,  strong  iron, 
havinsf  the  greatest  contraction  of  .10  to  .15  inch  more  in  the 
diameter  of  the  gun  tlian  lower  irons. 

165.  Want  of  Uniformity . — Cast-iron  is  far  from  being 
uniform  ; we  do  not  by  any  means  know  what  qualities  of  cast- 
iron  are  necessary  to  make  the  best  gun ; nor  if  we  did,  do  we 
know  absolutely  how,  from  any  of  its  ores,  constantly  to  pro- 
duce cast-iron  which  shall  possess  those  qiialities. 

The  difference  in  the  strength  of  the  highest  and  lowest 
gun-iron  tested  during  a series  of  years  (xki  t.  347),  is  stated  at 
about  37,000  pounds,  which  is  about  equal  to  tne  highest  cast- 
iron  of  commerce. 

This  want  of  uniformity  must  always  he  risked,  because  it 
cannot  positively  be  remedied.  Long  experience,  however, 
enables  founders  to  mix  iron  Avith  a great  degree  of  certainty 
as  to  the  intended  product,  but  no  two  charges  in  the  smelting- 
furnace,  or  pigs  broken  for  remelting,  can  be  relied  upon  as 
being  exactly  alike. 

166.  Identity  of  chemical  composition  may  coexist  in  dif- 
ferent specimens  of  cast-iron  with  great  variation  of  phvsical 
properties ; therefore  chemical  identity  does  not  involve  uni- 
formity in  the  mechanical  properties  of  cast-iron.  So  that,  how- 
ever desirable  it  may  be  to  ascertain  the  chemical  qualities, 
practical  men  are  very  far  from  accepting  them  as  indices  of  its 
tensile  strength. 


Experiments  on  Metals  for  Cannon,  etc.,  1861. 


54 


NAVAL  ORDNANCE  AND  GUNNERY. 


167.  Cost. — The  principal  argument  in  favor  of  cast-iron  as 
a material  for  guns,  is  its  cheapness  and  the  facility  Tvith  which 
it  can  he  produced  compared  with  Avrought-iron  or  steel.  To 
convert  and  shape  the  latter,  at  a great  expenditure  of  fuel  and 
labor,  wear  of  machinery  and  loss  of  machinery,  costs  in  Eng- 
land, where  prices  are  lowest,  twenty  to  forty  cents  per  pound; 
the  cost  of  large  guns  increasing  faster  than  their  weight ; 
melting  cast-ii’on,  preparing  the  molds,  and  dressing  the  sur- 
faces already  shaped,  can  he  done  from  seven  to  thirteen  cents 
per  pound,  which  is  about  half  the  cost  of  Avrought-iron  for  a 
given  calibre.  But  calibre  is  not  always  a measure  of  work. 

168.  Qualities  of  IYeougiit-iuox. — Strength. — lYrought- 
iron  being  comparatively  rehned  is  not  necessarily  so  vanons 
in  quality  as  cast-iron,  and  is  very  much  stronger.  Its  perma- 
nent yielding-point  is  higher  than  the  breaking-point  of  cast- 
iron,  and  its  breaking-point  is  double  that  of  its  yielding-point. 
The  average  tensile  strength  of  the  best  qualities  of  wrought- 
iron  is  about  60,000  pounds  per  square  inch,  or  about  double 
that  of  the  best  qualities  of  cast  gun-iron. 

169.  Uniformity. — xYlthougli  there  is  a wide  range  of 
strength  between  the  highest  and  lowest  specimens  of  Avrought- 
irou,  it  is  practically  much  more  uniform  than  cast-iron  ; that  is 
to  say,  the  iron  for  a given  sendee  can  be  selected  with  much 
more  certainty.  The  wrought-iron  from  any  particular  maker, 
who  is  careful  in  the  manufacture,  is  found  to  he  nearly  uni- 
form. 

170.  Detection  of  Weahness. — Unmistakable  evidences  of 
failure  Avhen  it  approaches,  is  obviously  an  important  quality  in 
any  cannon  metal.  The  detection  of  the  coming  fracture  of 
cast-iron  guns  may  undoubtedly  be  determined  from  minute 
cracks  in  the  bore,  and  from  close  inspection  of  the  gradual 
enlargement  of  the  vent.  But  from  the  fact  that  cast-iron 
breaks  in  the  testing-machine  at  the  instant  of  perceptible  elon- 
gation, these  evidences  must  be  more  or  less  vague. 

Wrought-iron  continues  to  stretch  after  the  point  of  peiana- 
nent  elongation,  and  the  margin  which  lies  between  the  point 
of  yielding  permanently  and  the  point  of  ultimate  rupture  is 
of  great  importance  as  a condition  of  safety. 

171.  Resistance  to  Compression  and  Wear. — Another  im- 
portant quality  of  cannon  metal  is  that  the  material  shall  he 
sufficiently  hard  so  that  the  surface  of  the  interior  of  the  bore 
shall  not  in  anyway  be  indented  or  bruised,  or  otherwise  acted 
upon  by  the  poAvder  or  the  projectile,  or  even  by  the  premature 
fracture  or  explosion  of  a shell  Avithin  the  bore. 

The  bores  of  wronght-iron  guns  have  been  permanently 


CANISTON  METALS. 


55 


indented  by  moderate  firing.  This  is  a great  objection  to 
wrougbt-iron,  and  it  becomes  a serious  defect  under  the  high 
pressures  which  heavy  guns  have  to  endure. 

The  hardness  of  metals,  their  resistance  to  abrasion,  such  as 
the  wear  of  projectiles,  approximates  to  their  resistance  to  com- 
pression. The  average  hardness  of  steel  is  highest,  and  that  of 
wrought-iron  lowest.  Cast-iron  is  well  adapted  for  this  pur- 
pose. 

172.  Want  of  Homogeniety. — The  grand  defect  of  wrought- 
iron  is,  that  it  is  not  homogeneous.  The  puddling  process,  by 
which  it  is  produced,  the  piling  process,  by  which  large  masses 
are  aggregated,  and  the  welding  process,  by  which  all  parts, 
large  and  small,  are  united,  are  all  the  means  of  interposing 
strata  of  impurities  and  planes  of  weakness. 

In  fabricating  guns,  the' first  necessity  is  the  production  of  a 
large  mass  of  material.  While  melted  cast-iron  and  steel  run 
into  castings  of  any  size  by  their  own  gravity,  wrought-iron  is 
not  melted  at  a practicable  heat,  so  that  another  process  must 
be  resorted  to.  If  the  gun  is  forged  solid,  the  process  consists 
in  adding  a little  at  a time  rrnder  the  hammer,  and  trimming 
off  a great  deal  of  scrap.  Many  weeks  are  occupied  in  forging 
a heavy  gun.  If  the  gun  is  huilt-vp,  small  pieces  are  fitted 
together  with  tools  at  a still  greater  cost.  When  all  this  is 
done  it  is  not  homogeneous. 

173.  Qualities  of  Steel. — High  Steel. — Its  distinguishing 
properties  are  extreme  ultimate  tenacity,  hardness,  and  capabil- 
ity of  extension  without  permanent  change  of  figure ; but  its 
extensibility  beyond  the  elastic  limit  is  small,  and  it  is  therefore 
brittle  under  concussion.  It  will  harden  when  heated  and  im- 
mersed in  water ; it  is  with  difficulty  welded,  because  it  deteri- 
orates under  high  heat,  and  because  its  welding  heat  is  very 
near  its  melting  point,  and  it  is  melted  at  a low  temperature 
compared  with  wrought-iron. 

Its  obvious  defect  for  cannon  is  its  brittleness,  but  if  so 
large  a mass  is  used  that  its  elastic  limit  wdll  never  be  exceeded, 
or  if  it  is  jacketed  with  a less  extensible  metal,  this  defect  is 
remedied  or  modified. 

171.  Low  steel  is  a more  snitable  metal  for  cannon.  It  can 
be  welded  without  difficulty,  although  over-heating  deteriorates 
it,  and  it  more  nearly  resembles  wrought-iron  in  all  its  proper- 
ties, although  it  has  much  greater  hardness  and  ultimate  tenacity, 
and  a lower  range  of  ductility,  depending  on  its  proportion  of 
carbon.  It  has  less  extensibility  within  the  elastic  limit  than 
high  steel,  but  greater  extensibility  beyond  it,  that  is  to  say,, 
greater  ductility. 


56 


NAVAL  ORDN^iNCE  AND  GUNNERY. 


175.  The  grand  advantage  of  low  steel  over  wroiight-iron, 
for  nearly  all  purposes,  is,  that  it  can  be  melted  at  a practicable 
heat  and  run  into  large  masses ; thus  avoiding  the  serious  de- 
fect of  wrought-iron  in  large  masses — want  of  soundness  and 
homogeniety. 

Its  other  important  advantages  for  cannon  are : greater  elas- 
ticity, tenacity,  and  hardness. 

if  steel,  or  any  metal  requiring  the  highest  attainable  effort 
of  force  in  motion  to  stretch  it  within  its  elastic  limit,  could  also 
be  made  to  have  a great  range  of  ductility  beyond  it,  the  safest 
and  most  perfect  cannon  metal  would  be  obtained.  But  unfor- 
tunately as  the  one  property  increases  the  other  decreases. 

Elasticity  is  an  indispensable  quality  in  hoops,  especially 
when  the  inner  barrel  is  of  cast-iron  or  a slightly  ductile  metal. 
If  hoops  change  their  figure  permanently,  their  usefulness  is  in 
a great  degree  destroyed.  For  a given  elongation  without  per- 
manent change  of  figure  high-steel  requires  more  “ work  done  ” 
than  any  other  metal. 

176.  StTength. — The  tensile  strength  of  steel  ranges  all  the 
way  from  50,000  to  200,000  pounds. 

The  strength  of  low  steel,  adapted  to  cannon-making,  aver- 
ages about  90,000  pounds,  or  three  times  that  of  the  best  cast- 
iron.  The  superiority  of  steel  as  regards  hardness  is  too  evident 
to  require  comment,  and,  considering  the  friction  of  riiie  projec- 
tiles and  the  enormous  pressure  that  modern  cannon  are  required 
to  stand,  this  is  by  no  means  an  unimportant  quality. 

177.  Bronze. — -The  work  done  in  stretching  to  the  elastic 
limit,  and  the  point  of  fracture,  is  less  for  ordinary  bronze  than 
for  wrought-iron  of  maximum  ductility,  and  for  low  steel.  This 
defect,  added  to  the  costliness  of  bronze,  to  the  various  embar- 
rassments experienced  in  the  casting  of  large  masses,  its  softness 
and  consequently  rapid  wear  and  compression,  and  to  its  injury 
by  heat,  has  not  warranted  its  employment  for  large  calibres 
and  high  charges. 

178.  The  mean  ultimate  cohesion  of  bronze,  according  to 
European  authorities  and  the  experiments  of  the  ITuited  States 
government  is  about  33,000  pounds  per  square  inch. 

179.  Billed  bronze-guns  would  be  naturally  more  liable  to 
rapid  deterioration  than  smooth  bores,  as  the  weights  of  projec- 
tile and  (^harge  are  much  greater  in  the  former  in  comparison  to 
the  area  acted  upon,  and  consequently  the  local  heating  at  the 
seat  of  the  charge  is  much  more  intense,  thus  tending  to  separate 
the  copper  and  tin,  more  or  less,  from  each  other,  forming  those 
tin  spots  and  porous  patches  which  iujure  the  strength  of  the 
material.  The  reduction  of  windage  also,  in  the  riffe-gun,  would 


CANNOI^  METALS. 


57 


tend  to  increase  this  local  heating,  and  it  must  he  remembered 
that  bronze  becomes  hot  very  easily,  and  tin  melts  very  soon 
(44-2°  F.) ; moreover,  the  grooves  in  a rifle-gun  open  out  many 
tin  spots  which  would  remain  nnexposed  in  a smooth-bore. 

180.  Conclusions. — The  fitness  of  metals  for  cannon  de- 
pends chiefiy  on  the  amount  of  their  elongation  within  the 
elastic  limit  and  the  amount  of  pressure  required  to  produce 
this  elongation,  that  is  to  say,  upon  their  elasticity. 

It  also  depends,  if  tlie  least  possible  weight  is  to  he  com- 
bined with  the  greatest  possible  preventive  against  explosive 
bursting,  upon  the  amount  of  elongation,  and  the  correspond- 
ing pressure,  beyond  the  elastic  limit ; that  is  to  say,  iqion  the 
ductility  of  the  metal. 

Hardness  to  resist  compression  and  wear  is  the  other  most 
important  quality. 

181.  Cast-iron  has  the  least  ultimate  tenacity,  elasticity,  and 
ductility ; but  it  is  harder  than  bronze  or  wrought-iron,  and 
more  uniform  and  trustworthy  than  wrought-iron,  because  it  is 
homogeneous. 

The  unequal  cooling  of  solid  castings  leaves  them  under 
initial  rupturing  strains  ; but  hollow  casting  and  cooling  from 
within  remedies  this  defect  and  other  minor  defects. 

182.  Wrought-iron  has  the  advantage  of  a considerable 
amount  of  elasticity,  a high  degree  of  ductility,  and  a greater' 
ultimate  tenacity,  than  cast-iron ; but  as  large  masses  must  be 
Avelded  up  from  small  pieces,  this  tenacity  cannot  be  depended 
upon  ; this  defect,  however,  is  more  in  the  process  of  fabrication 
than  in  the  material,  and  may  be  modified  by  improved  pro- 
cesses. Another  serious  defect  of  wrought-iron  is  its  softness 
and  consequent  yielding  under  pressure  and  friction. 

183.  Low  cast-steel  lias  the  greatest  ultimate  tenacity  and 
hardness ; and  what  is  more  important,  with  an  equal  degree  of 
ductility  it  has  the  highest  elasticity. 

It  has  the  great  advantage  over  wrought-iron  of  homogenie- 
ty  in  masses  of  any  size. 

It  is,  unlike  the  other  metals,  capable  of  great  variation  in 
density,  by  the  simple  processes  of  hardening  and  annealing, 
and,  therefore,  of  being  adapted  to  the  difterent  degrees  of 
elongation  that  it  is  subjected  to,  in  either  solid  or  built-up 
guns. 

184.  Bronze  has  greater  ultimate  tenacity  than  cast-iron, 
but  it  has  little  more  elasticity  and  less  homogeniety ; it  has  a 
high  degree  of  ductility,  but  it  is  the  softest  of  cannon-metals, 
and  is  injuriously  affected  by  the  heat  of  high  charges. 

185.  In  view  of  the  duty  demanded  of  modern  guns,  it 


58 


NAVAL  ORDNANCE  AND  GUNNERY. 


wovilcl  seem  that  simple  cast-iron  is  too  weak,  although  it  can 
be  used  to  advantage  for  jackets  over  steel  tubes.  And, 
although  cast-iron  barrels,  hooped  with  the  best  high  wronght- 
iron,  and  with  low-steel,  cannot  fulfil  all  the  theoretical  condi- 
tions of  strength,  and  do  not  endure  the  highest  charges,  they 
have  thus  far  proved  trustworthy  and  efficient. 

Wronght-iron  in  large  masses  cannot  he  trusted,  and  is  in  all 
cases  too  soft. 

Bronze  is  impractically  soft,  and  destructible  by  heat. 

Low-steel  is,  therefore,  by  reason  of  the  associated  cpialities, 
which  may  be  called  strength  and  toughness,  probably  the  only 
material  from  which  we  can  hope  to  maintain  resistance  to  the 
high  pressures  demanded  in  modern  warfare. 

ISG.  The  necessity  for  strength  in  any  gun  construction 
depends  upon  the  amount  of  stiffin  that  is  brought  upon  it,  and 
this  strain  is  affected  by  the  method  and  rate  at  which  the  gases 
are  evolved  in  the  burning  of  the  powder-charge,  and  the  rate 
at  Avhich  the  powder-space  behind  the  projectile  is  enlarged  by 
the  gradual  movement  of  the  projectile  through  the  bore. 

it  is  evident  that  if  by  any  proper  manipulation  of  the  pow- 
der in  manufacture,  the  size,  form,  and  density  of  the  grain  can 
be  so  determined  and  adjusted  as  to  confine  the  strain  within 
certain  limits,  the  strength  of  the  gun  to  resist  such  a strain  need 
not  reach  the  maximum  requirements  of  steel,  but  may  be  found 
within  the  well-known  capabilities  of  our  best  cast-iron. 


CHAPTEE  II. 


GENERAL  DESCRIPTION  OF  ORDNANCE. 

Section  I — Terms  and  Definition. 

187.  Ordnance. — The  terra  Ordnance  includes  artillery  of 
all  kinds  in  its  most  comprehensive  signification. 

Classification. — Ordnance  is  divided  into  three  general 
classes,  viz. : guns.,  mortars.,  and  howitzers. 

188.  GUES. — In  a technical  sense,  a gain  is  a heavy  cannon. 
Guns  are  nsed  for  firing  projectiles  at  very  low  angles,  with  large 
charges,  to  obtain  high  initial  velocity. 

They  are  distinguished  as  rifie  and  smootlidyore  cannon,  as 
east  and  built-itp  cannon,  and  as  breech-loading  and  muzzle- 
loading cannon. 

Smooth-bore  cannon  are  of  two  kinds,  solid-shot-guns  and 
shelVguns. 

Solid-shot-gnns  are  distinguished  hy  the  weight  of  the  pro- 
jectiles, and  shell-guns  by  the  diameter  of  the  bore. 

Shell-guns  possess  the  advantage  of  being  lighter  pieces,  and 
yet  firing  shells  of  as  large  diameter. 

189.  A gun  of  ordinary  construction  is  cylindro-conical  in 
general  form.  As  the  strain  upon  the  piece,  when  discharged, 
decreases  from  breech  to  muzzle,  the  thickness  of  metal  may  be 
proportionately  reduced,  and  advantage  thus  gained  of  lessening 
the  weight  of  the  gun  without  impairing  its  efficiency. 

The  greater  part  of  the  effect  of  the  charge  is  sustained  hy 
the  heavy  cylindrical  portion,  the  other  part  of  the  gun  being 
principally  a directing  tube. 

190.  N OMEN CLAT  UKE. — Guns  may  generally  he  divided 
into  five  principal  parts,  viz. : Breech.,  Cylinder,  Curve,  Chase, 
and  Muzzle.  (Eigs.  15  and  16.) 

191.  The  Breech  is  the  mass  of  solid  metal  in  rear  of  the 
bottom  of  the  bore. 

The  thickness  of  metal  in  the  prolongation  of  the  axis  of 
the  bore  is  of  superior  importance,  for  if  a gun  be  weak  there, 
strength  in  other  parts  will  not  save  it  from  explosion. 


60 


NAVAL  ORDNANCE  AND  GENNERT. 


The  thickness  is  usuallj  somewhat  gi’eater  than  the  greatest 
thickness  of  metal  in  the  cylinder. 

In  the  Dahlgren  pattern  the  hemispherical  portion  in  rear  of 
the  base-line  is  struck  from  a centre  at  the  bottom  of  the  cham- 
ber, Avith  a radius  ecpial  to  the  greatest  semi-diameter  of  the 
piece. 


Fig.  15. — Dalilgren  Shell-^un. 


Scale  of  1809, 


Length  of  gn-in,  A K. 

hemisphere 


Breech,  A M, 
including— 


AL. 


or  base  of 
breech, 
casoabcl,  L M. 
jaws,  e f. 

block  and  pin,  m m. 


Cylinder,  A C. 
Curve,  C H. 
Chase,  II  I. 


Muzzle,  I 
Bore,  a c, 


y j swell  of  muzzle, 
^ *j  c,  fnce  of  piece, 
j cylinder,  b c. 

I gomer  chamber,  a 6. 


Base  line,  A. 
Trunnion,  E F. 

Rim  base,  D G. 
Brecc.i  sight  mass,  k. 
Front  sight  mass,  1. 
Lockings,  g. 

Vent,  h t. 


192.  The  Cylinder  is  that  portion  between  the  breech  and 
trunnions,  including  the  seat  of  charge  and  the  point  where  the 
greatest  strain  is  exerted  upon  the  gun. 

A thickness  of  one  calibre,  or  the  diameter  of  the  boi’e,  was 
formerly  tlie  general  mle,  but  it  lias  been  found  insufficient  for 
lieaA^y  cast-iron  cannons.  The  results  of  experiments  show  that 
for  tlie  larger  calibre,  the  thickness  of  the  cylinder  should  not 
he  less  than  one  and  a quarter  times  the  diameter  of  the  bore, 
Avliile  no  important  increase  in  resistance  is  obtained  by  increas- 
ing the  thickness  of  the  metal  beyond  one  and  a haK  cahbres. 
(Art.  223.) 

193.  The  Curve  is  the  tnmeated  cone  connecting  the  cylin- 
der with  the  chase.  It  is  made  somewhat  thiclcer  than  necessary 
to  resist  the  pressure  of  the  powder,  in  order  to  serve  as  a 
proper  point  of  support  for  the  trunnions,  and  to  compensate  for 
certain  defects  of  metal  liable  to  occur  in  the  A'icinity  of  the 
trunnion  of  all  cast  cannon  arising  from  the  ciystalline  arrange- 
ment and  unequal  cooling  of  the  different  parts.  (Art.  366.) 

191.  The  Chase  is  the  long,  tapering  portion  of  the  gun  ex- 
tending from  the  curve  to  the  muzzle.  The  principal  injury  to 


GENEEAL  DESCRIPTION  OF  ORDNANCE. 


61 


wliieli  the  chase  is  liable  arising  from  the  striking  or  balloting 
of  the  projectile  against  the  side  of  the  bore,  in  smooth-bored 
cannon  ; and  the  thickness  of  metal  should  be  sufficient  to  resist 
it.  In  pieces  of  soft  iron  or  bronze  the  indentation  thus  made 
may  increase  to  the  extent  of  bursting  the  piece ; but  in  cast- 
u’on  cannon,  where  they  are  always  very  slight,  the  taper  of  the 


Fig.  1C.— Parrott  Rifle-gun. 
Scale  of  18(i9. 


C F,  curve,  N P,  coscabel.  h /«,  rim  base. 

F K,  chase.  a c,  bore. 

C K is  straight  in  eight-inch  guns, 

chase  can  be  made  more  rapid,  or,  with  the  same  weight  of 
metal,  larger  than  in  bronze  guns. 

195.  The  Mxizzle  is  the  increased  thickness  of  metal  which 
terminates  the  chase.  Inasmuch  as  the  metal  situated  imme- 
diately at  the  muzzle  is  supported  only  in  rear,  it  has  been 
usually  considered  necessary  to  increase  its  thickness  to  enable  it 
to  resist  the  action  of  the  projectile  at  this  point,  but  in  late 
cannon  designed  to  fire  through  embrasures,  the  swell  of  the 
muzzle  has  been  omitted.  The  swell  strengthens  a part  liable 
to  be  impaired  by  an  enemy’s  fire,  and  affords,  also,  a good  posi- 
tion for  a notch  or  sight. 

196.  The  Trunnions  are  two  cylindrical  arms  attached  to 
the  sides  of  a cannon,  for  the  purpose  of  supporting  it  on  its 
carriage.  They  are  placed  on  opposite  sides  of  the  piece,  with 
their  axes  in  the  same  line,  and  at  right  angles  to  its  axis. 

197.  Size. — The  size  of  the  trunnions  depends  on  the  recoil 
of  the  piece,  and  the  material  of  which  they  are  made. 

The  resistance  which  a cylinder  opposes  to  rupture,  is  pro- 
portional to  the  cube  of  its  diameter ; on  the  supposition  that 
the  strain  is  proportional  to  the  weight  of  the  charge,  it  is  usual 
to  make  the  diameter  of  the  trunnions  equal  to  the  diameter  of 
the  bore. 


62 


NAVAL  OEDNANCE  AND  GTJNNEEY. 


198.  Position. — The  position  of  the  trunnions,  with  refer- 
ence to  the  axis  of  the  bore,  influences  the  amount  of  recoil 
and  the  endurance  of  the  carriage.  By  reference  to  Fig.  17,  it 
will  he  seen  that  if  the  axis  of  the  trininions  be  placed  below 
the  axis  of  the  piece,  the  resultant  of  the  force  of  the  charge, 

which  acts  against  the  bottom 
of  the  bore,  will  act  to  turn 

C — j — the  piece  around  its  timnnion, 

^ and  cause  the  breech  to  press 

Fig.  17.  upon  the  head  of  the  elevat- 

ing-screw, with  a force  pro- 
portioned to  the  length  of  the  lever-arm,  or  distance  between 
the  axes. 

The  efi^ect  will  be  to  throw  an  additional  strain  on  the  car- 
riage by  pressing  down  the  rear  part  of  it,  and  checking  the 
recoil. 

If  the  trunnions  be  placed  above  the  axis  of  the  piece,  rota- 
tion will  take  place  in  the  opposite  direction,  and  the  effect  of 
the  discharge  u]3on  the  carriage  and  recoil  will  be  reversed.  By 
placing  the  two  axes  m the  same  plane,  the  force  of  the  charge 
will  be  communicated  directly  to  the  trunnions,  without  increas- 
ing or  diminishing  its  effect  on  the  can  iage  or  recoil ; this  posi- 
tion is  given  to  them  in  all  cannon  of  the  United  States  service. 

199.  Preponderance. — The  unequal  distribution  of  the 
weight  of  a cannon,  with  reference  to  the  axis  of  the  trunnions, 
is  called  the  preponderance. 

It  is  the  pressure  which  the  breech  portion  of  the  gun, 
when  horizontal,  exerts  on  the  elevating  arrangement.  To 
ascertain  the  preponderance  practically,  support  the  gun  at  the 
trunnions  as  freely  as  possible,  and  bring  it  horizontal  by  means 
of  a long  hand-spike  in  the  bore.  Place  a platform  scales  under 
the  breech,  and  fix  a block  of  wood  on  it,  touching  the  gun  un- 
derneath at  the  elevating-point.  The  hand-spike  being  then 
removed  from  the  bore,  the  pressure  on  the  block  is  indicated 
on  the  arm  of  the  scales,  and  is  the  preponderance  of  the  srun. 
(Art.  318.) 

200.  The  Pim-l)ases  are  two  larger  cylinders  placed  concen- 
trically around  the  trunnions,  for  the  purpose  of  strengthening 
them  at  their  junction  with  the  piece,  and  by  forming  shoulders, 
to  prevent  the  piece  from  moving  sideways  in  the  trunnion-beds. 
The  ends  of  the  rim-bases,  or  the  shoulders  of  the  trunnions, 
are  planes  perpendicular  to  the  axis  of  the  trunnions. 

201.  INTERIOR  FORM. — Calibke.— The  diameter  of 
the  bore  is  termed  the  calibre  of  the  gun ; this  should  be  so 
regulated  that  there  may  be  no  waste  of  powder,  and  that  the 


GENERAL  DESCRIPTION  OF  ORDNANCE. 


63 


force  of  the  gas  may  be  expended  in  giving  velocity  to  the  pro- 
jectile with  as  little  strain  as  possible  on  the  metal  of  the  gnn. 

The  calibre  of  a piece  of  ordnance  depends  upon  the  foiTQ 
and  nature  of  the  projectile;  the  general  form  of  projectiles 
being  that  of  a sphere,  or  cylinder  (pointed),  it  is  obvious  that 
the  bore  of  a gun  should  he  cylindrical  in  shape,  except  when 
modihed  to  a certain  extent  by  a chamber,  or  riding. 

A rided  gun  requires  a less  calibre  than  a smooth-bored 
piece,  if  both  are  intended  to  dre  projectiles  of  equal  weight, 
for  with  the  former  elongated  projectiles  can  be  used,  hut  with 
the  latter  only  spherical. 

A gun  intended  only  for  shell  dring  has  a large  calibre  in 
proportion  to  its  weight,  capacity  of  shell  for  bursting  charge 
being  re:juisite. 

202.  The  calibre  must  also  be  suited  to  the  charge.  As  the 
diameter  of  the  bore  is  decreased,  so  with  a given  charge,  must 
the  length  of  the  cartridge  he  increased,  and  the  conversion  of 
the  powder  into  gas  be  retarded  unless  the  cartridge  he  pierced 
hke  a tube ; with  the  longer  cartridge  the  strain  will  be  thrown 
moi’e  forward. 

In  two  guns  of  different  calibres,  the  useful  effect  of  a given 
charge  is  probably  the  greatest  in  the  bore  of  the  higher  calibi’e, 
as  regards  the  initial  velocity  of  the  projectile,  for  as  the  gas 
exerts  a certain  pressure  per  square  inch  on  the  base  of  the  pro- 
jectile, the  one  with  the  larger  bore  will  receive  the  most  press- 
ure. 

As  the  calibre  of  the  gnn  is  increased,  so  will  the  bottom  of 
the  bore  receive  a greater,  and  the  metal  surrounding  the  charge 
a less  proportional  strain  for  a given  pressure  per  square  inch  ; 
hut  the  pressure  will  probably  increase  with  the  calibre,  imtil 
the  diameter  of  the  cartridge  is  about  equal  to  its  length,  on 
account  of  the  more  rapid  conversion  of  the  charge  into  gas. 

203.  Length  of  Bore.— The  length  of  the  bore  of  a piece 
of  ordnance,  must  be  such  as  to  allow  of  the  decomposition  of 
its  whole  charge,  a cei’tain  time  being  necessary  for  its  complete 
combustion.  If  the  bore  be  not  of  sufficient  length  for  this 
purpose,  a considerable  portion  of  the  charge  will  he  blown  out 
untired,  and  therefore  wasted. 

The  initial  velocity  of  the  projectile  increases  with  the  length 
of  bore  up  to  a certain  point,  viz. : when  the  retarchng  forces 
of  the  friction  of  the  ball  against  the  sides  of  the  bore,  and  the 
resistance  of  the  column  of  air  in  front  of  the  projectile  (which 
increases  with  the  velocity),  are  equal  to  the  accelerating  force 
of  the  gas,  it  follows  that  after  the  projectile  passes  this  point, 
its  velocity  decreases  until  it  is  finally  brought  to  a state  of  rest. 


G4 


NAVAL  ORDNANCE  AND  GUNNERY. 


204.  Experiments  have  been  made  with  smooth-bore  guns 
at  different  times,  to  determine  the  influence  the  length  of  the 
piece  exercises  on  the  velocity  of  its  projectile,  and  they  show 
that  the  velocity  increases  with  the  length  of  the  bore  in  a vari- 
able ratio,  the  increase  of  velocity  for  the  short  lengths  being 
much  greater  than  those  for  the  long  lengths. 

Experiments  made  by  Major  Mordecai,  U.S.A.,  on  a piece 
of  light  calibre,  show  that  the  velocity  increases  with  the  length 
of  the  bore  up  to  twenty-five  calibres,  but  that  the  entire  gain 
beyond  sixteen  calibres,  or  an  addition  of  more  than  one-half  to 
the  length  of  the  gun,  gives  an  increase  of  only  one-e'ghteenth 
to  the  effect  of  a charge  of  four  pounds. 

The  length  of  the  bore  is  always  limited  by  several  other 
practical  considerations,  such  as  the  weight  of  the  piece,  and  the 
space  it  will  have  to  occupy. 

205.  The  proper  length  of  bore  for  a rifle  cannon,  has  not 
been  satisfactorily  determined,  so  many  different  points  requir- 
ing numerous  and  careful  experiments,  in  order  to  furnish  suffi- 
cient data  for  the  proper  consideration  of  the  subject.  How- 
ever the  length  of  the  bore  of  a rifled  piece,  intended  to  fire  a 
given  charge  and  weight  of  projectile,  should  depend  upon  the 
calibre  and  system  of  rifling  adopted ; if  two  rifled  guns  are  re- 
quired to  fire  equal  charges,  but  one  has  a less  calibre  than  the 
other,  the  same  amount  of  work  will  not  probably  be  done  upon 
the  projectiles  in  the  two  boi  es,  unless  the  I’espective  lengths  of 
the  latter  are  nearly  proportioiral  to  the  lengths  of  the  cartrid- 
ges and  so  equal  expansion  is  allowed  to  the  gas  in  both  bores. 

In  some  systems  of  rilling  a greater  force  is  required  to 
move  the  projectile  than  in  others,  and,  consequently,  more  of 
the  powder  is  converted  into  gas  before  the  shot  starts ; also,  in 
most  of  the  breech-loading  rifled  guns,  there  is  no  windage,  and, 
there  being  no  loss  of  gas,  greater  force  is  exerted  in  a given 
space  than  where  there  is  windage. 

206.  Windage  is  the  space  left  between  the  bore  of  the 
piece  and  its  projectile,  and  is  measured  by  the  difference  of 
their  diameters. 

The  windage  is  strictly  the  difference  between  the  area  of 
a section  of  the  bore  at  right-angles  to  its  axis,  and  the  area  of 
its  great  circle  of  the  projectile,  but  the  linear  windage  is  given 
in  all  olEeial  tables  of  ordnance. 

207.  The  objects  of  windage  being  to  facilitate  loading,  and 
to  diminish  the  danger  of  biu'sting  the  piece,  it  is  rendered  nec- 
essary in  all  muzzle-loading  cannon,  by  the  mechanical  impos- 
sibility of  making  every  projectile  of  the  proper  size  and  shape, 
by  the  unyielding  nature  of  the  material  of  which  large  pro- 


GENERAL  DESCRIPTION  OF  ORDNANCE. 


65 


jectiles  are  made,  by  the  foulness  which  collects  in  the  bore 
after  each  discharge,  and  by  the  use  of  hot  and  strapped  pro- 

Windage  diminishes  the  accuracy  of  fire,  weakens  the 
effect  of  the  charge  by  allowing  an  escape  of  gas,  and  is  the 
principal  cause  of  deterioration  in  cannon.  It  is  therefore  of 
importance  to  make  the  windage  as  small  as  possible,  compati- 
ble with  ease  and  efficiency  in  loading. 

209.  The  velocity  of  projectile  and  recoil  of  gun  are  consi- 
derably less  as  the  windage  is  increased  ; experiments  indicate 
that  tiie  loss  of  velocity  by  windage  in  smooth-bore  guns,  is 
proportional  to  the  windage,  but  this  point  has  not  been  detei’- 
mined  for  rifle  guns. 

210.  The  amount  of  gas  which  is  lost  will  depend  upon  the 
form  of  the  projectile,  and  the  resistance  which  it  offers  to 
motion.  The  greater  the  force  required  to  move  the  projectile, 
the  longer  the  time  for  the  escape  of  gas,  so  that  the  waste 
should  increase  with  the  weight  of  projectile,  and  there  should 
be  a greater  loss  in  rifled  than  in  smooth-bored  cannon,  if  the 
calibre  and  windages  are  alike,  but  the  elongated  form  of  a pro- 
jectile will  tend  to  confine  the  gas  as  it  escapes  witliin  narrow 
limits,  and  by  retarding  its  motion  diminish  its  waste. 

211.  Seat  of  the  Cuaege. — The  form  of  that  part  of  the 
bore  which  contains  the  powder,  will  have  an  effect  on  the  force 
of  the  charge,  and  the  strength  of  the  piece  to  resist  it. 

Chamber. — The  chamber  of  a gun  is  the  contraction,  or 
cavity,  at  the  bottom  of  the  bore  to  receive  the  charge  of  pow- 
der. It  is  generally  conceded  that  chambers  are  not  advanta- 
geous except  with  charges  less  than  would  fill  a cylinder,  whose 
length  is  equal  to  the  diameter  of  the  bore. 

212.  When  a light  piece  is  used  to  throw  a projectile  of 
large  diameter  and  great  weight,  it  is  advantageous  to  employ 
a small  charge  of  powder.  If  such  a charge  was  made  into  a 
form  to  fit  the  bore,  its  length  would  be  less  than  its  diameter, 
and  being  ignited  at  the  top  a considerable  portion  of  the  gas 
generated  in  the  first  instant  of  inflammation,  would  pass 
through  the  windage,  and  a part  of  the  force  of  the  charge 
would  be  lost.  To  obviate  this  defect,  and  to  give  the  cartridge 
a more  manageable  form  in  loading,  as  well  as  to  strengthen 
the  gun,  the  diameter  of  this  part  of  the  bore  is  decreased  so 
as  to  form  a chamber. 

21 3.  Shape. — The  necessity  for  a chamber  being  assumed, 
and  its  capacity  decided  upon,  the  determination  of  its  proper 
form  will  be  governed  by  several  conditions.  First.  The 
chamber  must  be  deep  enough  to  receive  a cartridge  manage- 

5 


jectiles. 

208. 


(30  NAVAL  OEDNANCE  AND  GUNNEET. 

able  ill  lengtli.  Second.  As  the  tencleiiej  to  transverse  rupture 
varies  directly  as  the  scpiare  of  the  length  of  the  bore  subjected 
to  maximum 'pressure — and  as  the  chamber  adds  materially  to 
this  leno-th,  it  must  evidently  be  no  deeper  than  the  service  of 
the  guiTrenders  necessary.  Third.  It  should  contain  no  angles, 


on  account  of  the  well-known  tendency  of  a split  to  begin  at 
an  angle ; hence,  the  bore  should  terminate  iu  a curve,  the 
hemisphere,  semi-ellipsoid,  paraboloid,  and  ogival,  being  those 
most  frequently  used. 

214.  The  shape  of  the  chamber  generally  in  use  is  conical. 
The  particular  kind  of  chamber,  represented  in  Fig.  IS.  is  called 
a Gomer  Chamber  after  its  inventor.  Its  principal  advantages 
are,  that  of  distributing  the  force  of  the  charge  over  a large  por- 
tion of  the  surface  of  the  projectile,  thereby  rendering  it  less  lia- 
ble to  break  if  it  be  hollow,  and  that  of  destroying  tlie  windage 
when  the  projectile  is  driven  down  to  its  proper  place. 

There  are  two  forms  of  chambers  adapted  in  the  service. 
The  cylindrical  and  the  conical,  or  gomer.  The  first  is  nearly 
obsolete. 

215.  The  Yent  is  the  channel  passing  through  the  metal, 
from  the  exterior  of  the  breech  into  the  bore,  by  means  of  which 
the  gun  is  fired. 

The  size  of  the  vent  should  be  as  small  as  possible  in  order 
to  diminish  the  escape  of  gas  and  the  erosion  of  the  metal.  Avhich 
results'from  it.  In  Yaval  Ordnance  vents  are  constructed  two- 
tenths  of  an  inch  in  diameter. 

21G.  In  bronze  pieces  the  heat  of  the  inflamed  gases  would 
be  sufficient  to  melt  the  tin,  and  rapidly  enlarge  its  diameter. 


GE^^ERAL  DESCRIPTION  OF  ORDNANCE. 


67 


For  this  reason  tliej  are  honched  by  screwing  in  a perforated 
piece  of  pare  wrouglit-copper,  called  the  'Ve7>i-piec6.  (Fig.  19.) 
This  amingeinent  allows  the  vent 
to  be  renewed  when  too  much  en- 
larged by  continued  use.  Copper 
vent-pieces  are  especially  neces- 
sary in  rifle-guns,  in  consequence 
of  the  prolonged  action  of  the  gas 
arising  from  the  resistance  of  tlie 
projectile.  In  the  largest  calibre 
the  interior  orifice  is  lined  with 
platinum.  The  upper  portion  of 
the  copper  i's  replaced  by  steel  to 
obtain  a harder  surface  for  receiv- 
ing the  blow  of  the  hammer. 

217.  Position. — All  smooth- 
bore guns  of  the  Dahlgren  pattern 
have  two  unbouched  vents,  situated 
on  opposite  sides  of  the  axis  of 
the  bore,  and  inclined  at  an  angle  of  70°  with  that  axis. 
(Fig.  76.) 

The  one  on  the  right  side  is  bored  entirely  through ; the 
other  is  simply  initiated  to  give  it  direction. 

When  the  open  vent  is  too  much  enlarged  by  wear  for 
further  use  it  is  closed  with  melted  zinc,  and  the  other  is  bored 
out.  Each  vent  should  endure  about  live  hundred  service 
rounds.  (Art.  603.) 

In  smooth-bore  cast-guns  the  vent  enters  the  bore  v‘ery  near 
the  bottom  ; the  vmnts  of  heavy  built-up  guns  are  usually  bored 
vertically,  and  in  such  a position  as  to  strike  the  cartridge  at 
about  four-tenths  of  its  leng-th  from  the  bottom  of  the  bore,  it 
having  been  ascertained  by  experiment  that  the  ignition  of  the 
charge  at  about  this  point  realizes  the  greatest  projectile  force 
that  can  I'e  produced  by  a given  charge. 

Experiment  shows  that  the  actual  loss  of  force  by  the  escape 
of  gas  through  the  vent,  as  compared  to  that  of  the  entire  charge, 
is  inconsiderable,  and  may  be  neglected  in  practice. 

218.  Extekior  Form. — In  designing  a gun  it  is  necessary  in 
the  first  place  to  endeavor  to  determine  what  thickness  of  metal 
is  required  for  that  part  of  the  gun  surrounding  the  seat  of  the 
charge,  for  it  is  here  where  the  greatest  strain  from  the  explosion 
of  the  charge  is  exerted.  ISTo  precise  rules  can  be  laid  down  for 
tlie  regulation  of  this  thickness  in  various  kinds  of  oi’dnance,  as 
so  much  depends  upon  the  physical  properties  of  the  material 
used.  The  general  results  of  experience,  or  of  experiments,  car- 


68 


NAVAL  ORDNANCE  AND  GUNNEET. 


ried  on  for  the  pm-pose  of  establishing  this  point,  can  alone  fur- 
nish ns  with  the  recpiisite  data.  (Art.  221.) 

The  amount  of  metal  in  a gun  must  depend  upon  the  charge, 


Fig.  20. — IX-in.  Dahlgren. 


the  weight,  and  form  of  the  projectile,  the  material  used,  and 
the  method  of  construction. 

219.  Foece  to  be  kesteaixed. — ^TFhen  a charge  of  gunpow- 
der is  ignited  in  the  bore  of  a gun,  the  gas  exerts  ecpial  pressm-es 
in  all  directions,  and  therefore  neglecting  windage,  the  pressure 
in  the  bottom  of  the  bore  is  equal'to  that  on  the  base  of  the  pro- 
jectile, and  the  pressures  on  the  top  and  bottom  as  well  as  those 
on  the  sides  of  the  bore  balance  each  other. 

220.  The  metal  of  a gun  is  subjected  to  two  principal  strains 
(Art.  308),  one,  a transverse  or  tangential,  which  tends  to  rend 
the  metal  lengthwise,  or  from  end  to  end,  through  A,  B (Fig. 
21),  and  the  other,  a longitudinal,  tending  to  fracture  the  gim 

across,  as  through  C,  D (Fig. 
21),  or  to  chive  out  the 
g breech. 

As  the  projectile  moves 
towards  the  muzzle  so  will 
the  space  in  which  the  gas  is 
confined  be  increased,  and 
the  pressure  be  decreased ; the  portion  of  metal  surrounding 
the  space  originally  occupied  by  the  cartridge,  and  a little  in 
front  of  it,  is  that  upon  which  the  maximum  pressure  from  the 
gas  is  exerted. 

The  maximum  pressure  will  be  influenced  by  the  nature^  of 
the  powder,  the  resistance  ofl’ered  by  the  projectile  to  motion, 
and  by  the  absence  or  amount  of  windage. 

221.  Expeeijients. — Many  experiments  have  been  made  to 
determine  the  gradual  decrease  of  strain  upon  the  metal  of  a 
piece  of  orchmnce,  from  breech  to  muzzle.  The  first  were 


D. 


— 1 



C 


Eig.  21. 


GENERAL  DESCRIPTION  OF  ORDNANCK 


69 


accomplished  bj  perforating  a gun  in  several  places  from  the  ex- 
terior to  the  bore,  at  right  angles  with  the  bore,  and  successively 
screwing  a pistol-barrel,  containing  a steel  ball,  into  each  perfora- 
tion, and  discharging  the  gun  with  the  pistol-barrel  at  the  diJier- 


Fig.  22. — Heavy  Twenty-Pounder  Bronze  Rifle,  1,950  lbs. 


ent  perforations,  the  relative  velocities  with  which  the  pistol-ball 
(received  by  a pendulum)  is  forced  out  at  these  different  positions 
indicate  the  force  exerted  there  to  burst  the  gun ; and  conse- 
quently the  relative  strength  of  metal  necessary  in  the  various 
parts  to  resist  explosion. 

The  results  of  these  experiments  are  relatively  as  follows,  in 
decimal  parts : 


At  a calibre  in  rear  of  centre  of  projectile 98 

“ centre  of  projectile 1. 

“ one  calibre  in  front  of  projectile 81 

“ two  “ “ “ 68 

“ three  “ “ “ 62 

“ five  “ “ “ 53 

“ seven  “ “ “ 44 

“ nine  “ “ “ 40 

“ eleven  “ “ “ 37 

“ fifteen  “ “ “ 29 


These  decimals  show  the  relative  strength  necessary  at  differ- 
ent parts  to  resist  explosion. 

The  dimensions  here  given  are  intended  to  apply  to  cast-iron 
ordnance,  which  it  was  assumed  should  have  a thickness  of  one 
calibre  round  the  seat  of  the  charge  where  the  greatest  strain  is 
exerted. 


70 


KAVAL  OEDNAIfCE  AND  GUNNERY. 


22'2.  Other  experiments  have  been  made  hj  using  Rodman’s 
pressure  gauge  (Art.  1332)  in  the  holes  instead  of  a pistol-barrel, 


Fig.  23. — Navy  XV-incli. 


also  using  electricity  by  connecting  a chronoscope  rvith  wh-es  in 
plugs  titted  in  the  holes  of  the  gun.  (Art.  1302.) 

223.  In  cast-iron  guns  of  more  recent  construction  tire  metal 
is  distributed  on  diherent  principles,  viz. : in  giving  a greater 
thickness  of  metal,  and  consequently  more  strength  about  the 
seat  of  the  charge,  vdiile  the  amount  of  metal  in  the  chase  is 
diminished,  this  part  having  to  sustain  but  a small  proportion  of 
the  strain  from  the  discharge  of  the  piece;  also,  in  increasing 
the  proportional  thickness  of  metal,  as  the  calibre  of  the  gun  is 
greater.  (Art.  311.) 

221.  iMPnovEJiENTS. — Gun-making  is  no  longer  the  simple 
matter  which  it  continued  to  he  while  the  Avorld  was  content 
vrith  wooden  ships  and  round  shot.  There  are  now  almost  as 
many  ways  of  making  a gun  as  of  making  a steam  engine.  In-' 
genuity  has  been  exercised  upon  the  material,  the  construction, 
the  rifling,  and  the  mounting  of  the  gun,  as  also  in  regard  to  the 
kind  of  powder  with  which  it  is  to  be  loaded,  the  structure  of 
the  projectile  which  is  to  he  fired,  and  the  appliances  by  which 
the  gun  is  to  be  worked.  Everything  is  changed  since  the  days 
when  simple  smooth-bores  and  cannon-balls  were  deemed  sutii- 
ciently  formidable  and  destructive. 

After  many  years  of  experiment  and  millions  of  expenditure 
foreign  powers  have  established  two  or  three  systems  of  I'ifled 
ordnance  as  worthy  of  confidence.  These  are  the  German  sys- 
tem (Art.  701',  the  Erench  system  (Art.  (573),  and  the  English 
system  (Art.  6(51). 

In  our  country  appropriations  have  been  made  for  carrying 
on  experiments  with  a view  to  establishiug  the  best  system  of 
heavy  rifled  ordnance.  The  Army  has  been  entrusted  with  this 


GENERAL  DESCRIPTION  OF  ORDNANCE. 


71 


important  duty,  and  experimental  guns  on  different  plans  are 
now  in  course  of  construction. 

225.  Devices. — Formerly  cannon  were  liiglily  ornamented 
with  figures  representing  some  fanciful  design,  together  with  the 
national  coat-of-arms  and  cypher  of  the  reigning  monarch.  Each 

Fig.  21. — DaUgren  Shell  Gun. 


piece  also  bore  a particular  name,  borrowed  from  some  animal 
or  passion  ; and  sometimes  mottoes  were  inscribed  upon  them. 
The  most  recent  models  are  characterized  by  an  entire  absence  of 
molding  or  ornaments,  and  by  the  utmost  simplicity  of  ffgure. 

22G.  (See  Table  facing  jiage  71,  and  marked  71'^.) 

227.  MORTARS. — Mortars  are  short  pieces  of  ordnance 
with  large  bores,  used  to  throw  shells  at  high  angles,  generally 
forty-five  degrees,  for  reaching  objects  by  their  vertical  fire. 
They  are  used  in  the  navy  only  under  exceptional  circum- 
stances. 

228.  CoxsTEcrcTioN.— They  are  constructed  stronger  than 
guns,  on  account  of  the  high  elevation  at  which  they  are  fired ; 
and  shorter,  because  the  difficulty  of  loading  would  be  increased 
by  their  length.  In  the  new  patterns,  the  axis  of  the  trunnions 
passes  through  the  centre  of  gravity,  if  the  piece  and  the  bore 
is  unchambered. 

The  only  mortar  used  in  the  naval  service,  is  the  thirteen 
inch  of  17,000  lbs.,  made  of  cast-iron.  (Fig.  25.) 

229.  ITowitzers. — Properly,  howitzers  are  a description  of 
shell-guns  ; shorter,  lighter,  and  more  cylindrical  in  shape  than 


72 


NAVAL  ORDNANCE  AND  GUNNERY. 


a gun  of  tlie  same  calibre,  and  having  a chamber  for  the  recep- 
tion of  the  powder.  They  are  employed  to  fire  large  projec- 
tiles at  low  angles,  with  comparatively  small  charges  of  powder. 


Fig.  25. 


230.  Kaval  rioAvuTZERS  are  bronze  shcll-gnns,  adapted  to 
field  and  boat  service.  They  are  made  of  bronze  on  account  of 
their  comparative  lightness  for  the  same  strength,  and  from 
their  being  less  liable  to  burst  than  iron  guns  of  the  same 
calibre. 

231.  The  Bo.^t  Howtizees  are  both  smooth-bore  and  ride. 


Fig.  23. — Light  Twelve-Pounder  Boat  Howitzer. 


They  are  alike  in  the  principle  of  construction  and  general 
appearance,  and  differ  only  in  weight  and  dimensions. 


GENERAL  DESCRIPTIOiSr  OF  ORDNANCE. 


73 


Around  the  charge  the  metal  is  distributed  in  form  of  a cyl- 
inder (Fig.  26),  extending  sufficiently  in  front  of  the  seat  of  the 
projectile  ; thence  to  the  muzzle  it  is  continued  as  a truncated 
cone. 

The  breech  is  a portion  of  a sphere.  The  bore  is  terminated 
by  a conical  chamber  (Fig.  18),  and  the  piece  is  mounted  on  its 
carriage  by  a loop. 


Fig.  27. — Rifled  Twelve- Pounder  Bronze  Howitzer. 

232.  Pekcussion-Locks  ”^foe  Naval  Okdnance. — The  ham- 


N.  An  iron  nipple  with  a case-hardened  face  screwed  into  the  head. 

A.  The  hole  for  the  axial  bolt  of  the  hammer. 

A B.  The  extension  of  the  hole,  termed  a slot,  in  the  direction  of  the  head 
H;  its  length  is  such  as  to  admit  of  the  hammer’s  receding  one  inch,  which 
takes  it  entirely  clear  of  the  vent-blast. 

L.  A laniard  entering  beneath  the  rear  end  of  the  shank,  which  is  rounded 
for  that  purpose,  then  through  a perforated  stud  (Y)  on  the  under-side  of  the 
shank. 

mer  has  its  revolution  about  the  axial  bolt  traversing  the  hole 
A,  and  the  force  is  applied  by  the  laniard  passing  about  the 
rounded  rear  end  of  the  shank.  When  the  hammer  is  thrown 
hack,  the  laniard  being  steadily  and  quickly  drawn,  compels 
the  hammer  to  turn  on  its  holt  until  down  on  the  vent.  Aow, 
if  there  were  no  other  perforation  for  the  bolt  than  that  at 
A,  the  hammer  could  not  escape  from  the  gas  issuing  out  of 
the  vent,  and  must  be  thrown  otf  by  it.  But  when  the  ham- 
mer is  down,  if  the  force  of  the  laniard  he  continued,  the  effort 


L 


Fig.  28. — H.  Tbe  head  of  the  hammer.  ' 


S.  The  shank. 


74 


NAVAL  ORDNANCE  AND  GUNNERY. 


is  to  withdraw  directly  from  the  vent,  and  the  slot  or  extension 
of  A permits  this  to  he  done  until  the  end  of  the  slot  at  B is 
arrested  by  the  axial  bolt.  The  receding  motion  thus  obtained 


has  the  extent  of  one  inch,  which  is  sufficient  to  take  the  ham- 
mer-head clear  of  the  blast  of  the  vent. 

A lock-mass  is  cast  with 
the  gnn  near  the  vent 
(Fig.  22).  It  is  slit  so  as 
to  form  studs,  between 
which  the  hammer  is  se- 
cured and  has  its  move- 
ment. 

On  boat-howitzers  the 
lock  has  no  slot,  and  does 
not  recede  from  the  vent. 
The  vent-blast  is  avoided 
b}'  having  a perforation  in 
the  head  of  the  liammer ; which  allows  for  its  escape  without 
throwing  back  the  lock. 

233.  THE  GATLIHG-GUH — (Fig.  32) — is  a machine-gun 
consisting  of  a set  of  ten  barrels.  A,  in  combination  witli  a 
grooved  cartridge  carrier,  M,  and  a lock-cylinder,  O and  O' 
(Fig.  36).  The  whole  being  rigidly  secured  to  a centre-shaft, 
H.  The  grooves  in  the  carrier,  the  holes  in  the  lock-cylinder, 
and  the  barrels,  all  correspond  in  number.  Each  barrel  is  pro  ■ 
vided  with  a lock,  F (Fig.  37),  which  works  in  a chamber 
formed  in  the  lock-cylinder;  O and  O',  in  a line  with  the 
axis  of  the  barrels.  The  lock-cylinder  is  surrounded  by  an 
outer  casing,  II,  connected  to  the  framing,  B,  which  is  carried 
along  on  each  side  of  the  barrels  and  across  the  front  of  the 
gun ; the  rear  end  of  each  side  frame  forming  a support  for 
the  breech-casing,  II.  In  the  breech-casing  is  a verticle  trans- 


THE  GATLIXG-GIESr. 


75 


’s^erse  partition,  D (Fig.  39),  into  wliicli  tire  main  central  shaft, 
17,  n'liich  carries  the  loch-cylinder,  O,  carrier  M,  and  barrels.  A, 
is  journalled.  At  its  front  end  the  main  shaft  is  also  journalled 
into  the  cross-piece  of  the  frame,  B. 


23-1:.  On  the  rear  end  of  the  main  shaft  is  fixed  the  revolt- 
ing gear  (Fig.  39),  which  is  worked  by  a crank,  G,  on  the 
right  side  of  the  breech-casing,  H.  The  rear  of  the  chamber  in 
which  the  gear  is  placed  is  closed  by  a cascabel  plate,  C (Fig. 
37),  having  an  opening  through  which  the  lock  may  be  entered 


Fig.  33. 


and  withdrawn  when  necessary.  This  opening  is  closed  by  a 
plug  of  special  construction,  E,  attached  to  the  cascabel  plate  by 
a chain. 

In  front  of  the  breach-casing  and  hinged  to  the  frame,  B, 
is  a curved  plate,  I (Fig.  31),  called  the  hopper^  through  which 
the  cartridges  are  fed  to  the  gun. 


76 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  gun  is  mounted  on  a swivel  block,  L (Fig.  32),  on  which 
are  formed  seats  to  receive  the  trunnions  of  tlie  gun  ; this 
block  is  secured  to  the  carriage  by  a centre-pin,  which  allows  it 
to  turn  and  bring  the  gun  to  bear  upon  any  object  within  the 
arc  of  twelve  degrees,  the  trunnions  permitting  vertical  motion 
of  the  muzzle  of  the  gun, 

235.  The  IIoppek  (Fig.  34)  is  a brass  curved  plate,  I, 

hinged  to  the  frame-work 
of  the  gun  on  the  right  side 
and  encasing  the  chambers 
of  the  barrels.  It  is  pro- 
vided with  an  aperture,  K, 
through  which  the  cartrid- 
ges descend  to  their  places 
in  the  grooves  of  the  car- 
rier or  chambers  of  the  bar- 
rels ; Avhereupon  they  are 
instantly  taken  possession 
of  by  the  locks,  forced  into 
the  barrels,  and  bred.  A 
short  distance  in  fi’ont  of 

the  cartridge  aperture,  is  an  upright  pin  I',  in  which  the  feed 
drum,  Y (Fig.  42),  rests  and  revolves.  The  upper  side  of  the 
hopper  is  flat  and  circular. 

236.  The  Apertuke,  K (Fig.  42),  for  the  cartridges,  is  nearly 
of  the  form  of  a cartridge  and  tapered  downward.  Its  sides 
serve  to  guide  the  cartridges  into  the  carrier  singly,  so  that  they 
can  be  removed  one  by  one.  The  front  end  of  the  aperture  is 
projected  downward  nearly  into  the  carrier  next  the  barrels, 
and  thus  serves  to  cut  otf  the  entrance  to  that  particular  barrel 
which  is  in  front  of  it,  Avhile  in  this  position;  and  prevents  the 
cartridge  which  lies  upon  the  one  already  in  the  groove  from 
sliding  forward  and  prematurely  entering  the  opposite  barrel. 

237.  The  Carrier,  M (Fig.  35),  is  a metal  cylinder,  attached 
to,  and  revolving  with,  the  main  shaft ; its  for- 
ward edge  being  sutficiently  near  the  rear  end  of 
the  barrels  to  insure  the  cartridges  entering  with- 
out jamming  (Fig.  42).  On  its  circumference  are 
as  many  grooves  as  there  are  barrels,  in  Avhich  the 
cartridges  rest  and  are  pushed  forward  into  the 

Fig.  35.  barrels  by  the  locks ; thus  the  grooves  of  the  car- 
rier act  as  chambers  for  the  barrels  (Fig.  33). 

238.  The  Lock-cylixder,  O and  O'  (Fig.  36),  is  a metal 
piece,  consisting  of  tivo  cylinders  of  different  diameters,  0,  and 
O'.  On  the  circumference  of  the  smaller  and  parallel  with  the 


THE  GATLING-GHH. 


77 


Fig.  30. 


axis  of  tlie  barrels,  are  as  many  slots  as  there  are  lochs,  and  in 
these  slots,  the  lug  on  the  underside  of  the  loch-case,  P (Fig. 
37),  travels.  In  the  larger  cylinder.' 
and  in  line  with  the  axis  of  the 
barrels,  are  the  same  number  of 
holes,  in  which  the  lochs  move  for- 
ward and  bach.  A slot  or  opening 
is  made  between  the  holes  and  the 
circumference  of  the  cylinder,  form- 
ing a guide  for  the  lug,  cc,  on  the 
firing-pin,  Z (Fig.  37),  of  the  loch. 

239.  The  Locks  consist  of  hollow  steel  cylindi’ical  cases  of 
different  diameters, 

F (Fig.  37);  the 
larger  cylinder,  or 
rear  part  of  the  loch- 
case  being  open  at 
the  top  for  a portion 
of  its  length.  In 
this  portion  is  placed 
the  firing-pin  and 
spring,  Z,  the  for- 
mer, which 


Fig  37. 


IS  re- 


duced in  diameter  at  its  forward  end  to  about  one-eighth  of 


an 


inch,  passes  through  the  smaller  portion  of  the  loch-case,  W, 
and  projects  very  slightly  beyond  it.  The  spring,  Z,  is  confined 
between  the  end  of  the  slot  and  a lug,  cb,  formed  at  the  forward 
end  of  the  larger  part  of  the  firing-pin.  This  lug  is  designed 
to  tahe  against  the  coching-plate  in  the  breach-casing  and 
gradually  press  the  spring  and  firing-pin  bachward,  until  the 
proper  moment,  when  it  is  released  and  the  firing-pin  is  thrown 
violently  forward,  exploding  the  cartridge. 

Attached  to  the  loch-case,  on  the  under  side,  are  two  lugs,  P, 
intended  to  travel  in  the  slot  on  the  circumference  of  the  small- 
er portion  of  the  loch-cylinder  O'  (Fig.  36).  At  the  rear  upper 
side  of  the  case  is  a lug,  y?,  which  tahing  against  the  cam  sur- 
face, P,  in  the  breach-casing,  (Fig.  38),  communicates  a for- 
ward and  bachward  motion  to  the  loch. 

On  the  upper  left-hand  side  of  the  loch-case  (Fig.  37),  is 
fixed  a piece  of  steel,  a,  about  four  inches  long,  called  the  Ex- 
tractor^ having  its  forward  edge  rounded  on  the  upper  side  and 
a shoulder  on  the  latter,  strihes  a cam  just  at  the  edge  of  the 
barrel,  drops  over  the  rim  of  the  cartridge,  and  when  the  loch 
moves  bach,  brings  the  cartridge-shell  with  it  and  di’ops  it  on 
the  ground  beneath  the  gun. 


78 


NAVAL  ORDNANCE  AND  GUNNERY. 


2-10.  The  Breech-casing,  II  (Fig.  38  and  Fig.  39),  is  a 
hollow  cylinder  extending  from  the  front  end  of  the  lock-cylin- 
der to  the  rear  portion  of  the  frame,  B.  Flanges,  A A,  on  its  sides 

rest  on  and  are  screwed  to 
the  frame  (Fig.  32);  near 
the  rear  end  is  a partition 
called  the  dia_phragm-plate, 
D (Fig.  39),  which  divides 
the  cylinder  into  two  parts 
and  separates  the  lock- 
cylinder  and  worm  gear, 
which  is  placed  in  the  rear 
portion  of  the  casing.  A 
cascabel  plate,  C (Fig.  37), 
screws  to  the  rear  end  of 
Fig.  38.  the  casing  and  serves  to  en- 

case and  protect  the  worm  or 
revolving-gear.  In  the  forward  division  of  the  casing  are  placed 
the  cams,  B (Fig.  38),  for  forcing  forward  and  drawing  back 
the  locks.  In  the  upper  left-hand  side  of  the  diaphragm-plates 
is  an  aperture,  d (Fig.  39),  through  which  the  lock  passes  when 
entered  or  withdrawn  ; a brass  tube,  e,  screwed  to  the  aperture, 
serving  as  a guide  to  the  lock  and  breach-plug.  At  the  proper 
distance  from  the  front  end  of  the  casing,  and  on  the  right  side, 
is  placed  a cocking-plate,  which  will  be  explained  under  the  heacl 
of  cocking  apparatus. 

2-11.  The  Bevolving  or  'Worm-gear  (Fig.39  ). — To  the  rear 
end  of  the  main  staff  passing  through  the  diaphragm-plate,  D, 
is  fixed  a worm-wheel,  W,  worked  by  a shaft,  S,  extending 
across  the  rear  portion  of  the  casing.  On  this  shaft  is  a worm, 
s,  which  works  in  the  worm-wheel,  W.  A crank,  G,  at  the  right 
end  of  the  transverse  shaft  conveys  motion  by  means  of  the 
-worm  to  the  worm-wheel,  and  thus  the  lock-cylinder,  carrier,  and 
barrels  are  revolved. 

212.  Traversing-gear. — To  the  opposite  side  of  the  trans- 
verse shaft  on  which  the  crank,  G (Fig.  39),  is  fitted,  is 
keyed  a sleeve,  t,  having  cut  on  its  exterior  a right  and  left- 
hand  screw,  on  -which  works  the  tapered  end  of  a forked  piece, 
T.  This  is  dropped  into  a socket,  in  the  outer  end  of  a brass 
casting,  FT,  against  which  the  upper  end  of  the  elevating- 
screw  presses  at  Ub  The  fork,  T,  passes  through  the  upper 
socket,  then  through  a brass  ring  fitted  with  a clamji,  T', 
and  finally  through  the  lower  socket  of  the  casting,  by  which 
means  the  fork  is  permitted  to  turn  as  it  passes  along  the 
cross-cut  thread,  t,  in  either  direction.  Fig.  10  represents  the 


THE  GATLIXG-GUN. 


79 


fork  detached  and  enlarged,  and  also  in  its  proper  position  on 
the  sleeve. 

On  the  onter  end  of  the  sleeve  is  keyed  a ring,  capable  of 
adjustment  at  every  half  turn  of  the  cross-cut-thread.  This  is  ef- 
fected by  a pin  on  the 
ring,  and  correspond- 
ing holes  midway  be- 
tween the  intersec- 
tion of  the  threads  of 
the  screws,  thus  reg- 
ulating the  range  of 
motion  of  the  breach 
of  the  gun.  This  ring 
serves  to  close  one 
end  and  thus  make 
the  screw  endless, 
and  also  to  turn  the 
fork  into  the  return 
groove,  the  inner  end 
of  the  sleeve  being 
arranged  so  as  to  ac- 
complish the  same 
object. 

' As  the  firing-crank,  G,  is  turned,  the  bands,  carrier,  lock-cyl- 
inder and  right  and  left-hand  screw  are  revolved.  The  latter, 
Avorking  on  the  fork,  T,  gives  the  piece  a continuous  lateral  trav- 
erse which  may  be  enlarged  or  contracted 
as  desired,  by  means  of  the  ring,  t' ; thus 
sjareading  the  fire  over  a wide  range,  or 
contractnig  it. 

Elevating  or  depressing  the  gnn  does 
not  interfere  with  the  lateral  traverse,  as 
the  elevating  screw  presses  against  the 
bottom  of  the  casting  to  which  the  fork  is  attached,  and  thus 
both  run  up  or  doAvn  alike. 

2±3.  The  Elevating-gear  (Eig.  32)  consists  of  a screw 
Avhose  loAver  part  rests  npon  the  trail  of  the  gun,  and  whose 
upper  part  ends  in  a ball,  Avorking  in  a socket,  tJ^  (Fig.  39),  on 
the  under  side  of  the  brass-casting,  U.  On  the  upper  surface  of 
the  casting  is  a rib  which  Avorks  in  a corresponding  slot,  in  a 
square  brass  plate,  U",  screwed  to  the  under  side  of  the  breech- 
casing. By  referring  to  Fig.  39,  the  arrangement  of  the  ele- 
vating and  revolving  gear  Avill  be  readily  understood. 

2f4.  The  movement  of  the  Locks  is  accomplished  bv  means 
of  two  spiral  cams,  E,  (Fig.  38),  placed  in  the  breech-casing  and 


80 


NAVAL  ORDNANCE  AND  GUNNERY. 


a slot  in  the  casing  itself,  along  the  edge  of  the  cams.  As  the 
crank,  G (Fig.  39),  is  turned,  the  rear  Ing,^  (Fig.  37),  on  the 
lock-case  travels  in  the  slot  along  the  spiral  cam,  forcing  the 
lock  forward  on  the  lock-cylinder  and  carrier.  The  front  end 
taking  against  the  cartridge  in  the  carrier,  pnshes  it  into  the 
barrel.  At  the  moment  that  the  cartridge  has  fully  entered  the 
barrel  the  lug,  x (Fig.  37),  in  the  firing-pin  takes  against  the 
cocking-plate  and  forces  back  the  spring,  z.  When  the  lug,  a?,  on 
the  pin  passes  the  highest  point  of  the  cocking-plate,  the  pin 
flying  forward  explodes  the  cartridge.  The  rear  Ing,  having 
then  reached  the  highest  point  of  the  spiral-cam,  R,  moves 
straight  forward  a short  distance  and  then  enters  the  slot  of  the 
other  cam  and  is  drawn  back  to  its  original  position.  The  same 
occurs  as  each  lock  arrives  at  the  cam  and  slot. 

245.  Removing  the  Locks. — The  locks  are  removed  and  in- 
serted through  an  aperture,  cut  in  the  cascabel  and  dia- 
phragm plates  (Figs.  37  and  39).  Both  these  apertures  are 
closed  by  a brass  breech-plng,  E (Fig.  37),  which  is  inserted  from 
the  rear  through  the  cascabel-plate,  C.  This  plug  carries  at  its 
front  end  a sleeve,  E',  which  has  a projecting  cone,/)  on  the 
under  side  of  which  is  cut  a slot.  When  the  plug  is  in  position 
in  the  gun,  this  slot  forms  a continuation  of  a groove  cut  in  the 
rear  chamber,  and  in  which  a lug  formed  on  tlie  rear  end  of  each 
lock  revolves.  When  the  lock  is  brought  into  line  with  the 
plug,  by  means  of  the  outside  handle,  G,  which  is  indicated  by 
an  arrow  on  the  hopper,  I,  and  a line  on  the  rear  brass  barrel- 
plate,  the  Ing,  y>,  on  the  lock  engages  in  the  slot  on  the  arm  of 
the  ping,  and  on  the  latter  being  ivithdrawn,  the  lock  follows. 
The  sleeve,  E^  is  connected  to  the  body  of  the  ping  by  a pin 
formed  with  the  ping,  and  around  which  it  is  just  free  to  re- 
volve without  being  a close  fit.  To  withdraw  the  plug,  it  is  first 
partially  rotated  so  as  to  bring  the  lug  by  which  it  is  locked 
opposite  the  aperture,  the  sleeve  still  retaining  its  hold  on  the 
lock  to  be  extracted,  and  being  retained  against  it  by  a spiral 
spring,  which  is  interposed  between  the  plug  and  the  sleeve. 
The  lock  and  sleeve  are  guided  into  the  aperture  in  the  dia- 
phragm-plate by  a tube,  having  a slot  in  its  upper  side, 
through  which  the  sleeve,  E',  of  the  plug  passes,  carrying  the 
lock  with  it. 

246.  Cocking  the  Locks  is  accomplished  by  means  of 
an  inclined  spiral  cocking-plate,  projecting  on  the  inner  side  of 
the  breech-casing,  so  that  when  the  lock  is  moved  forward,  a luir, 
a?,  formed  on  the  tiring-pin,  is  arrested  by  it,  the  spring  of  the  loclc 
is  gradually  contracted,  and  the  firing-pin  drawn  back  into  the 
lock-case.  When  the  lug,  x,  passes  the  end  of  the  stationary 


THE  GATLING-GUN. 


81 


Fm.  41. 


The  cartridges 


coehing-plate,  it  is  suddenly  released,  relieving  the  spring,  s, 
which  forces  the  pin  violently  forward  and  explodes  the  car- 
tridge. As  the  cocking-plate  is  stationary  and  the  lugs,  x,  re- 
volve with  the  locks,  tlie  cocking-plate  acts  upon  the  firing-pins, 
in  the  several  locks  successively,  causing  the  discharge  of  each 
barrel,  as  its  lock-lug  passes  the  plate. 

217.  The  Feed-dkum  Y (Fig.  41),  consists  of  a metal  fram- 
ing of  cylindrical  shape,  hav- 
ing any  convenient  number 
of  divisions  or  slots  (usually 
sixteen)  around  its  circumfer- 
ence, radiating  from  the  cen- 
tre. Each  division,  Y',  con- 
tains twenty-five  cartridges, 
placed  one  above  the  other  in 
a horizontal  position,  Y" 

(Fig.  42).  A hole  in  the  een- 
ti’e  of  the  drum  fits  over  a 
pin,  I',  on  the  hopper,  I. 

The  cartridges  are  fed  to  the 
carrier,  M,  below,  and  thence  to  the  barrels,  A. 
pass  to  the  hopper 
through  an  aperture  at 
the  bottom  of  each 
division  of  the  drum. 

On  the  bottom  face  of 
the  drum  and  to  the 
left  of  the  hopper  is  a 
projecting  rib, 
which  fits  into  the  slot, 
li',  on  the  hopper-plate 
to  steady  the  drum 
when  firing.  On  its 
lower  periphery  the 
drum  has  a series  of 
thumb-lugs,  m (Fig. 

41),  by  which  it  is  re- 
volved. A small  brass 
weight  in  each  division 
is  caused  to  bear  upon 
and  slide  down  a 
groove  provided  for  it, 
so  that  it  follows  the  cartridges  as  they  descend,  and  prevents 
their  becoming  choked  in  the  divisions.  In  firing  the  gun  the 
man  at  the  drum  brings  one  of  the  thumb-lugs,  m,  coincident 
6 


Fig.  43. 


82 


NAVAL  OEDNANCE  AND  GENNERT. 


with  the  rib  on  the  hopper-plate,  the  one  at  the  crank  revolves 
the  barrels  and  carrier,  and  the  cartridges  drop  into  the  hop- 
per from  one  division  nntil  it  becomes  empty.  The  operator 
then  reverses  the  drum  one-sixteenth  part  of  its  circumference, 
bringing  the  next  lug  over  the  rib,  and  at  the  same  time  the 
next  division  of  cartridges  over  the  hopper ; the  feed  thus  con- 
tinues until  the  whole  number  of  divisions  are  emptied,  when  a 
full  drum  replaces  the  empty  one,  and  the  firing  continues.  A 
locking  arrangement  is  provided  for  retaining  the  drum  in  posi- 
tion when  not  in  use. 

2d8.  To  Fill  the  Feed-drum. — Invert  and  unlock  it,  turn 
the  bottom-plate,  Y (Fig.  42),  until  the  hole  in  the  plate  comes 
directly  over  a division  of  the  di-um,  then  raise  the  brass  weight 
and  fill  in  the  rtirtridges  regularly,  letting  the  weight  descend 
slowly  until  the  division  is  full.  Proceed  in  like  manner  witli 
the  remaining  divisions ; then  lock  the  plate  and  place  the  drum 
upright. 

249.  The  Working  of  the  Gun. — One  man  places  the  feed- 
drum  filled  with  cartridges  on  the  hopper-plate,  with  the  two 
apertures  coinciding ; another,  at  the  firing-crank,  revolves 
it,  which,  by  means  of  tlie  worm-gear,  revmlves  the  main  shaft, 
carrying  with  it  the  lock-cylinder,  carrier,  barrels,  and  locks. 
As  the  carrier  revolves  the  cartridges  in  the  drum  drop  one  by 
one  into  the  grooves  of  the  carrier.  Instantly  the  lock,  by  its 
impingement  on  the  spiral  cam  in  the  breech-casing,  moves  for- 
ward, pushing  the  cartridge  into  the  barrel,  and  when  the  lug 
on  the  firing-pin  passes  the  highest  point  of  the  cocking-plate 
the  charge  is  fired.  As  soon  as  this  occurs,  the  lock  is  drawn 
back  by  the  sphal  cam  in  the  breech-casing,  bringing  with  it  the 
shell  of  the  cartridge,  after  it  has  been  fired,  which  is  di’opped 
upon  the  ground  beneath. 

250.  Thus,  when  the  gun  is  revolved,  the  locks  in  rapid  suc- 
cession move  forward  to  load  and  fire,  and  returning  extract  the 
cartridge-shells.  The  whole  operation  of  loading,  closing  the 
breech,  discharging,  and  expelling  the  empty  cases  is  thus  con- 
ducted while  the  barrels  are  kept  in  continuous  revolving  move- 
ment. In  operating  the,  gun,  firing  in  succession,  there  is  no 
accumulation  of  recoil,  and  therefore  no  resighting,  or  relaying 
the  gun,  necessary  between  each  discharge.  When  once  sighted 
its  carriage  does  not  moi'e,  except  at  the  will  of  the  operator. 
The  gun  can  be  moved  laterally  while  firing  is  going  on  so  as  to 
sweep  the  sector  of  a chcle  of  12°,  or  more,  without  moving  the 
trail  or  changing  the  -wheels  of  the  carriage. 

251.  Its  locks  are  made  interchangeable,  strong,  and  durable  ; 
but  should  they  get  out  of  order,  they  can  be  replaced  by  new 


THE  GATLIXG-GXJN. 


83 


ones  in  a very  few  moments.  The  loch  mechanism  is  the  only 
portion  liable  to  derangement,  the  other  parts  being  protected,  or 
of  sufficient  strength  to  withstand  all  usage  incident  to  the  service. 

253.  The  feed-drums  are  not  absolutely  necessary,  except  at 
close-quarters,  and  are  likely  to  cause  a wasteful  expenditure  of 
ammunition;  the  drums  being  liable  at  any  time  to  become 
deranged  and  wmrk  badly. 

The  crew  should  therefore  be  exercised  at  feeding  the  gun 
by  hand,  in  which  ease,  all  that  is  necessary  is  for  one  man,  A^  hen 
the  hopper  is  turned  back,  to  lay  the  cartridges,  one  at  a time, 
into  the  grooves  of  the  carrier.  The  revolving  of  the  crank 
loads  and  lires  the  gun. 

253.  When  rapid  lire  is  continued,  the  piece  becomes  heated, 
and  the  barrels  are  liable  to  bind  and  prevent  the  free  working 
of  the  gun;  recourse  is  then  had  to  the  adjustment-nuts  in  the 
front  of  the  barrels.  These  must  be  eased  up  sufficiently  to  en- 
able the  barrels  to  revolve  freely,  care  being  taken  that  the  crank 
is  fastened  to  prevent  the  possibility  of  the  piece  being  fired 
while  the  adjustment  is  being  made. 

254:.  In  firing,  the  crank  must  be  turned  steadily,  in  a uni- 
form manner,  and  not  too  rapidly ; otherwise  the  cartridges  will 
jam  in  the  carrier,  and  thus  elfectually  stop  the  fire  until  they 
can  be  removed. 

The  cartridge  used  is  the  same  as  that  of  the  ISTavy  Hifle,  .5 
in.,  and  the  arm  is  efiective  to  the  same  distance — about  1,200 
yards. 

255.  In  exercising  on  board  ship  the  locks  should  be  removed 
to  avoid  unnecessary  snapping  of  the  spring,  and  the  cartridges 
can  then  be  run  through  the  hopper  at  Avill,  familiarizing  the 
men  Avith  the  use  of  the  arm  Avithout  Avasting  ammunition. 

256.  It  is  believed  that  the  “ Gatling  ” cannot  be  substituted 
for  the  “IIoAvitzer”  in  boats,  therefore  no  boat-carriage  is  pro- 
vided, the  instability  of  the  boat  causing  the  continuous  fire  (the 
great  feature  of  the  gun)  to  be  extremely  scattering,  Avhile  the 
shrapnel  or  canister  from  its  Howitzer  is  delivered  only  Avhere 
the  gun  points. 

In  smooth  Avater  it  may  be  used  as  a boat-gun  by  removing 
the  wheels,  resting  the  axles  on  the  gunwale,  Avith  the  trail  of 
the  carriage  under  the  fonvard  thwart. 

257.  Theseevation. — The  Gatling  Gun,  although  an  intri- 
cate piece  of  mechanism  to  put  into  the  hands  of  seamen,  is  not 
liable  to  get  out  of  order  in  use,  or  have  its  parts  deranged,  un- 
less tinkered  Avith  by  the  quarter-gunner.  It  is  not  injured  by 
being  Avet  in  handling,  or  liable  to  be  clogged  with  sand  or  mud, 
provided  it  is  cleaned  and  dried  before  the  next  firing. 


84 


NAVAL  OEDNANCE  AND  GUNNERY. 


258.  The  gun  should  never  be  taken  apart  unless  absolutely 
necessaiy,  and  then,  if  possible,  by  a competent  mechanic,  under 
the  supervision  of  an  oliicer.  It  should  be  kept  free  from  mst, 
dust,  and  moisture,  and  oiled  frecpiently,  using  line  sperm-oil. 

When  it  is  possible,  before  firing,  the  barrels  and  can-ier 
should  be  wiped  and  cleaned ; in  doing  this  the  crank  should  be 
reversed  to  avoid  unnecessary  snapping. 

259.  DlliECTIONS  FOE  TAEIING  THE  GuN  APAET. 

1st.  Take  out  the  locks.  To  do  this,  turn  the  breech-plug  so 
that  the  marks  upon  it  and  the  cascabel-plates  correspond ; then 
turn  the  crank  until  one  of  the  marks  on  the  rear  brass  barrel- 
plate  is  brought  in  line  witli  the  arrow  on  the  hopper,  and  then 
pull  out  the  plug,  which  will  bring  out  a lock.  Ee-insert  the 
plug,  and  repeat  the  operation,  until  all  the  locks  are  removed. 

2(^.  Take  off  the  cascabel-plate,  which  is  screwed  to  the 
breech-casing. 

Zd.  Eemove  the  crank-axle  ; first  taking  off  the  traversing- 
screw  and  worm,  which  are  fastened  to  the  shaft  by  a screw  and 
a taper-pin  through  it ; then  remove  the  worm  gear. 

\th.  Take  out  the  screws  that  fasten  the  casing  to  the  frame. 

5^A.  Eaise  the  barrels  a very  little  by  means  of  the  assem- 
hling^est  ; then  remove  the  breech-easing. 

260.  Dieections  foe  purriNG  the  Gun  togethee. 

1st.  Put  the  axis  in  its  place  through  the  plates  which  hold 
the  barrels,  and  then  put  to  their  places  the  carrier-block,  lock- 
cylinder,  and  large  rear-nut.  The  last  should  be  screwed  up  tight, 
and  have  the  taper-pin  put  through  the  nut  and  sliaft. 

2f?.  Place  the  gun  within  the  frame,  and  let  the  front  end  of 
the  axis  rest  in  tlie  hole  designated  for  it,  in  tlie  front  of  the 
frame;  then  adjust  the  assembling-rest,  and,  in  this  position,  the 
breech-casing  can  be  shoved  over  the  lock-cy Linder  to  its  proper 
place  ; then  screw  the  casing  to  the  frame. 

Zd.  Put  on  the  worm-gear,  replace  the  crank-axle,  etc.,  and 
then  prrt  on  the  cascabel-plate.  Eevolve  the  crank  to  the  right 
or  left  until  one  of  the  marks  on  the  barrel-plate  is  brought  in 
line  with  the  arrow  on  the  hopper,  and  then  insert  a lock,  which 
is  shoved  to  its  place  by  the  plug.  Eemove  the  plug,  and  re- 
peat the  operation  until  all  the  locks  are  in  their  places. 

201.  THE  AEMAMENT  OF  SHIPS  OF  WAE."— The 
main  points  to  be  considered  in  determining  the  armaments  of 
ships  are : 

* Extracts  from  a paper  on  “ The  Armament  of  our  Ships  of  TTa?\”  by 
Captain  W.  N.  JefEers,  U.  S.  N.,  in  “The  Record  of  the  United  States  Navjd 
Institute,”  Vol.  I.,  1874. 


AK3IAMENT  OF  SHIPS. 


85 


First.  The  proportion  of  the  aggregate  weight  of  the  guns 
to  the  tonnage. 

Second.  To  dispose  of  this  weight  in  such  a manner  as  shall 
develo])  the  greatest  power  of  which  it  is  susceptible. 

Third.  The  relation  of  the  battery  to  the  speed  of  the  vessel. 

262.  I.  The  relations  of  weight  of  battery  to  tonnage  of 
ship  depends  upon  the  aggregate  assigned  to  ordnance  by  the 
constructor  in  distributing  his  weights ; and  the  weight  of  bat- 
tery Avhich  experience  shows  can  be  safely  and  conveniently 
carried,  is  from  one-third  greater  to  double  that  allowed  on  the 
given  displacement. 

263.  II.  Having  a ship  of  a certain  tonnage,  draft  of  water, 
and  speed,  with  so  many  tons  of  displacement  assigned  to  ord- 
nance ; the  question  is,  how  to  dispose  of  that  weight  to  the 
best  advantage,  distributing  it  with  a due  regard  to  the  neces- 
sary power  and  range  of  the  guns. 

261.  In  every  case  our  practice  is,  to  assign  the  smallest 
number  of  the  heaviest  guns  to  form  the  weight ; preferring 
pivot-guns  to  those  in  broadside  when  the  deck  arrangements 
will  permit,  because  the  former  are  always  more  under  com- 
mand than  the  latter ; and  it  is  thoroughly  established  that  a 
small  number  of  large  pieces  will  inflict  injuries  beyond  the 
power  of  a large  number  of  small  ones.  The  smallest  number 
and  heaviest  pieces  which  can  be  conveniently  handled  will 
then  form  the  armament. 

265.  One  of  the  first  elements  to  be  considered  is  the  abil- 
ity to  handle  the  projectile  in  the  confined  quarters  of  a ship 
subject  to  violent  motions  of  rolling  and  pitching.  Only  one 
man  can  conveniently  handle  the  projectile  of  a broadside  gun, 
and  but  two  that  of  a pivot ; and  experiment  proves  that  the 
nine-inch  and  eleven-inch  are  the  largest  shells  which  can  be 
so  handled  with  ease. 

266.  Ho  effort  should  be  spared  to  use  the  heaviest  calibre 
which  can  be  conveniently  carried,  and  any  obstacles  that  are 
removable  ought  to  be  made  to  give  way  without  scruple. 
The  celerity  of  fire  will  not  be  materially  affected,  and  the  su- 
perior calibre  always  possesses  superior  range,  accuracy,  and 
power. 

267.  III.  It  is  absolutely  necessary  that  a ship  of  war 
should  exercise  a full  power  of  offence  and  defence,  Avithin 
the  circle  of  which  she  is  the  centre : next  to  this,  and  to  this 
only,  in  importance  is  her  ability  to  transfer  this  power  to  an- 
other point. 

268.  In  order  that  a ship  may  exercise  her  full  measure  of 
offence,  speed  has  become  an  indispensable  attribute.  Without 


86 


NAVAL  ORDNANCE  AND  GUNNERY. 


it  lier  powers  are  altogether  incomplete ; and  expenence  appe  . . 
to  have  determined  that  it  is  jndieions  to  sacrilice  a large  por- 
tion of  the  armament  in  order  to  procnre  great  speed  at  any  cost. 

269.  When  a vessel  of  war  encoimters  a superior  force, 
speed  should  he  ahle  to  make  her  safe,  hut  the  necessary  dimi- 
nution of  offensive  power  should  not  be  so  great  as  to  disable 
a lirst-class  steamer  from  watching  any  vessel  of  her  own  class, 
of  inferior  speed,  but  provided  with  a proper  armament. 

270.  Our  vessels  of  war  sliould  have  equal  speed  with  those 
of  other  nations,  for  it  is  only  by  this  equality  that  they  can 
select  and  retain  the  distances  preferred.  If,  however,  our  ship 
is  inferior  in  speed,  then  the  choice  of  distance  is  with  the 
enemy,  who  is  supposed  to  prefer  close  quarters ; but  if  our 
ship  is  properly  armed  he  can  only  reach  this  position  after  pass- 
ing through  the  deliberate  fire  of  powerful  guns. 

271.  Kind  of  Gun. — The  armament  of  our  ships  of  war  con- 
sists mainly  of  smooth-bore  guns.  These  cannot  compete  with 
rifle-guns,  except  at  short  ranges,  their  eihciency  depending  on 
high  velocities,  which  the  resistance  of  the  air  greatly  diminishes  ; 
besides,  spherical  projectiles  are  deficient  in  weight,  and  their 
form  is  not  favorable  for  penetration. 

272.  With  wooden  shijDS,  the  mere  lodgment  of  a shell,  in 
the  side,  before  its  explosion,  is  sufficient  to  inflict  serious  injury  ; 
but  against  armored  ships  complete  perforation  is  essential.  Since 
the  general  introduction  of  armored  vessels,  the  conditions  of  war- 
fare hav'e  been  altered,  and  the  subject  of  penetration  has  be- 
come of  paramount  importance.  This  necessitates  the  intro- 
duction of  ride-cannon  as  the  entire  armament  of  our  ships. 

273.  The  principal  advantage  of  ride-cannon  consists  in  their 
greater  penetration,  due  to  the  concentration  of  effect  on  a 
smaller  and  better  form  of  surface ; next,  in  greater  explo- 
sive contents  for  the  same  weight;  then  range,  and  lastly, 
accuracy. 

271.  It  is  comparatively  easy  to  obtain  accuracy  to  such  au 
extent  as  is  sufficient  for  the  purposes  of  naval  warfare.  Under 
the  ordinary  circumstances  of  a naval  action,  the  probability  of 
striking  an  enemy’s  ship  is  dependent  far  more  on  an  accurate 
knowledge  of  the  distance,  on  the  steadiness  of  the  ship  carry- 
ing tlie  gun,  and  the  skill  of  the  man  who  dres  it,  than  on  the 
qualities  of  the  gun  itself. 

275.  Great  extent  of  range  is  one  of  the  especial  merits 
claimed  for  rided  ordnance.  But  the  instances  in  which  a great 
range  would  be  valuable  in  naval  war  are  of  such  rare  and  ex- 
ceptional occurrence,  that  it  is  not  an  important  requirement  in 
a good  naval  gun. 


THEORY  OF  GUN  CONSTRUCTION. 


8T 


Section  II — Theory  of  Oun  Construction! 

276.  THE  KIHDS  OF  STRAIHUPOH  A GUH.— There 
are : 

1st.  A tangential  strain.,  tending  to  split  the  gun  open  lon- 
gitudinally, and  similar  in  its  action  to  the  force  which  bnrsts 
the  hoops  of  a barrel. 

2c?.  A longitudinal  strain,  tending  to  pull  the  gnn  apart  in 
the  direction  of  its  length.  This  tendency  is  a maxiinnm  at  the 
bottom  of  the  bore,  and  diminishes  to  zero  at  the  muzzle. 

2>d.  A strain  of  compression,  exerted  from  the  axis  outward, 
tending  to  crush  the  truncated  wedges  of  which  a unit  of  length 
of  the  gun  may  be  supposed  to  consist,  and  to  diminish  the 
thickness  of  the  metal  to  which  it  is  applied. 

1th.  A transverse  strain,  tending  to  break  transversely  the 
staves  of  which  the  gun  may  be  supposed  to  consist,  and  similar 
in  its  action  to  the  force  which  breaks  the  staves  of  a barrel. 

277.  Tangential  Strain. — Barlow  shows  that  the  strain, 
produced  on  any  cylinder  by  the  action  of  a central  force, 
diminishes  as  the  square  of  the  distance  from  the  centre 
increases. 

The  demonstration  of  this  law  is  based  upon  the  hypothesis 
that  the  area  of  the  cross  section 
of  the  cylinder  to  which  the  force 
is  applied  remains  the  same  before 
and  during  the  application  of  the 
central  force. 

Assuming  this  to  be  true,  call 
A the  area  of  the  cross  section  of 
the  gun. 

In  Fig.  43,  let 
r — the  radius  of  the  bore, 
li  — the  radius  of  the  exterior, 
h = the  increase  of  the  internal 
radius, 

B — the  increase  of  the  exterior 
radius. 

Evidently, 

TtE^  — n!  = 7t{ir  — = A (1) 

or  IP  — ! — ^ (2) 

* Compiled  by  Lieutenant-Commander  C.  F.  Goodrich,  United  States 
Navy.  ’ 


88 


NAVAL  ORDNANCE  AND  GUNNERY. 


Differentiating  eq.  (2),  bearing  in  mind  that  A and  tt  are 
constants,  gives 

’iltdR  — %'dr  = o (3) 

Hence  RdR  — rdr t4) 

Multiplying  and  dividing  the  first  member  of  eq.  (4)  by  R, 
and  the  second  member  by  r,  and  substituting  for  dR  and  dr 
tlieir  values  B and  h,  gives 

R r ^ ' 


whence  the  proportion 

-:^  = Rd:r^ (a) 

278.  But  the  strain  produced  on  any  two  pieces  of  the  same 
material  will  be  proportional  to  the  increase  in  length  divided 
by  the  original  length  of  each  respectively — the  absolute  strain, 
for  a given  increase  of  length,  depending  upon  the  coefficient  of 

elasticity  of  the  material  strained.  Hence,  if  ^ be  the  strain 


on  the  exterior,  then  - is  that  on  the  interior.  It  will  therefore 

be  seen  from  the  proportion  (a)  that  the  strain  diminishes  as  the 
square  of  the  distance  from  the  centre  increases. 

279.  To  find  the  whole  resistance  of  the  gun-cylinder  to  the 
tangential  strain. 

Let  Fig.  44  represent  a section  of  a homogeneous  gun-eyhn- 

der. 


Take  C,  the  centre  of  the 
bore,  as  the  origin,  and  two 
lines  at  right  angles  to  each 
other  as  the  co-ordinate  axes. 
Denote  CA,  the  radius  of  the 
bore,  by  r,  and  CB,  the  exter- 
nal radius,  by  R. 

Me  may  represent  the  de- 
gree of  expansion  of  the  metal 
at  any  point  in  the  line  AB. 
caused  by  an  explosion  at  C,  bj 
an  ordinate,  erected  at  the  given 
point  proportional  in  length  to 
the  number  of  pounds’  strain 
at  that  point,  as  AH  ; similarly 
we  may  represent  a compres- 


sion by  a negative  ordinate,  as  AM. 

280.  Erecting  ordinates  in  this  manner  at  every  point  in  the 


THEORY  OF  GUH  CONSTRUCTION. 


89 


line  AB,  and  draAving  a line  tlirougli  their  extremities,  Ave  have 
the  curve  HL. 

From  BarloAv’s  LaAv  Ave  have  for  the  equation  to  this  curve 


y = 


,(6) 


Avhere  c is  a constant  depending  upon  the  force  exerted. 

To  obtain  the  form  of  this  curve  Avhen  the  expansion  is  at 
its  limit,  i.e.,  AA’hen  the  tenacity  of  the  metal  is  just  sufficient  to 
overcome  the  strain  at  A,  Ave  have  for  the  co-ordinates  of  the 
point  X — r,  y = S,  where  8 denotes  the  maximum  strain  in 
pounds.  Substituting  these  values  of  x and  y in  eq.  (6),  Ave  find 


>5=4 


G = 88^ 


and  the  equation  to  the  curve  is  therefore 

88 

y = ^ 


(b) 


281.  Taking  8 = 30,000  pounds,  r = 3 inches,  Ave  find 

for  a?  = 3 in.,  y = 30,000. 

a?  = 4 in.,  y = 16,875. 

£c  = 5 in.,  y = 10,800. 

X — Q in.,  y — 7,500. 

a?  = 7 in.,  y = 5,510. 

Thus  the  resistance  offered  by  each  part  of  the  cylinder 
diminishes  very  rapidly  as  the  distance  from  the  axis  increases. 

282.  As  the  ordinate  at  each  point  of  the  line  AB  measures 
the  resistance  of  the  gun  at  that  point,  the  sum  of  all  the  ordi- 
nates, or  the  area  of  the  curve  AHLB,  represents  the  entire 
tenacity  of  the  gun-cylinder. 

To  find  this  area  Ave  have 

^ =fydx (7) 

Substituting  the  value  of  y from  eq.  (b), 


88  

«/  00 

Intewratino:  betAveen  the  limits  H and  r, 

O O ' 


(8) 


“1 

-41 

L Xjr  1 

or 


A = 8r 


R — r 

~~W' 


(0) 


90 


NAVAL  OEDNANCE  AND  GUNNEEV. 


283.  Takins’  tlie  same  numerical  values  of  S and  r as  kefore. 


giving  different  values  of  ^ — 
the  gun), 

Jo  — r = 1 inch, 
J2  — r — 2 inches, 
Jo  — r = S inches, 
Jo  — r = 4:  inches, 
Ji  — r = 5 inches, 
Ji  — r = Q inches. 


(the  thickness  of  the  wall  of 

A = 22,500  lbs. 

A = 36,000  lbs. 

A = 45,000  lbs. 

A = 51,429  lbs. 

A = 56,250  lbs. 

A - 60,000  lbs. 


If  we  integrate  between  oc  and  r,  or,  what  is  the  same  thing, 
make  the  wall  of  the  gun  infinitely  thick, 

A = Sr (9) 


284.  ISTow  it  may  be  shown  that  the  whole  force  developed  by 
an  explosion,  to  burst  a gun  tangentially,  is  where  is  the 
pressure  of  the  gas  per  sqiiare  inch,  and  r the  radius  of  the  bore. 
But  we  see  from  eq.  (9)  that  the  greatest  possible  resistance 
of  the  cylinder  is  Sr ; therefore  when  an  explosion  takes  place, 
and  p is  greater  than  S,  the  cylinder  must  give  way.  That  is, 

thickness  of  metal,  however  great,  in  a homogeneous! y 
constructed  gun-cylinder,  can  withstand  an  expanding  force 
greater  than  the  absolute  tenacity  of  a bar  of  the  same  metaV' 

285.  To  find  the  tohole  force  exerted  oy  an  explosion  in  a 
cylinder  to  rend  it  longitudinally. 

Let  Fig.  45  represent  a section  of  a cylinder,  and  let  it  be 

required  to  find  the  force  ex- 
erted by  an  expanding  gas  to 
rend  the  cylinder  along  the 
line  AB.  Let  OA  = r,  the 
interior  radius  of  the  cylin- 
der, and  p denote  the  force 
the  gas  exerts  upon  a unit  of 
surface.  At  any  point,  as  P, 
the  gas  acts  in  the  line  OP. 
and  the  force  may  be  resolved 
into  tlie  components  Py  and 
Tx,  respectively  perpendicu- 
lar and  parallel  to  the  line 
AB.  The  sum  of  all  the 
forces  acting  perpendicularly  to  AB  is  the  force  requh’ed. 

Let  0 = the  angle  POA,  then  Py  = p sin  d. 

The  element  of  surface  is  rdd. 


The  required  force  F = f pr  sbi  Odd  — pr  f sin  Odd . . (10) 


THEORY  OF  GUN  CONSTRUCTION. 


91 


Taking  tlie  integral  between  and  o, 

2i 


F = pr (d) 

At  the  limit  of  endurance  the  rupturing  effort  will  be  equal 
to  the  whole  resistance  offered. 


^ R — r 

pr  — hr  — — 

(11) 

or 

^ = ^ It  

(e) 

/p 

Should  p become  greater  than  8 ^5— , the  gun  will  burst. 

J-i 

As  a particular  case,  let  the  wall  of  the  gun  be  one  calibre  in 
thickness,  i.e.,  R = S?*,  then 

= (f) 

Eupture  will  hence  ensue  in  this  gun  when  the  pressure  per 
square  inch  exceeds  two-thirds  of  the  tensile  strength  per  square 
inch  of  the  metal  of  which  it  is  constructed. 

28G.  Longitudinal  Stkain. — The  tendency  of  this  strain  is 
to  blow  the  breech  off. 

Expressions  for  the  rupturing  effort  of  tliis  strain,  and  the 
resistance  01  the  gun  to  it,  can  be  readily  found  based  upon  the 
assumption,  in  itself  highly  probable,  that  the  law  of  diminution 
of  strain  from  the  interior  outward  will  be  the  same  for  any 
central  section  of  the  sphere  of  which  the  breech  may  be  sup- 
posed to  consist  as  for  any  cross  section  of  the  gun. 

287.  To  find  the  Imigitudinal  rupturing  effort. — If  ^ be  the 
pressure  per  square  inch  at  the  bottom  of  the  bore,  the  whole 
rupturing  effort  in  the  direction  of  the  axis  of  the  gun  will  be 
p multiplied  by  the  number  of  square  inches  in  the  area  of  the 
bore,  or 

E = rcr'^P (g) 

288.  To  find  the  resistance  of  the  gun  to  the  longitudinal 
rupturing  effort. — This  will  evidently  be  the  sum  of  the  resist- 
ances to  longitudinal  separation  of  the  rings  of  metal  composing 
the  cross  section  of  the  gun,  at  the  juncture  of  the  breech  and 
cylinder. 

Let  r be  the  radius  of  the  bore. 

R be  the  radius  of  the  exterior  of  the  gun. 

8 be  the  tensile  strength  of  the  metal  per  square  inch. 


92 


NAVAL  ORDNANCE  AND  GITNNERY. 


Let  X be  the  radius  of  any  ring. 
dx  be  its  breadth. 

We  have  already  seen  that  the  resistance  to  an  internal  ex- 
plosive  force  at  any  point  of  the  wall  of  the  gun  is  S Hence, 
that  of  a ring  whose  radins  is  x,  and  breadth  dx,  will  be 
S — X ^TTxdx,  or  27tr^S  — . The  whole  resistance  of  the  wall 

X‘  X 

of  the  gun  will  be  found  by  integrating  this  expression  between 
the  Innits  and  : 


J %Ttr^  = 27ir^ S iWj?.  Log.  R — Nap.  Log.  r J . . (12) 


= 2/Tr'  S Nap.  Log. 


R 

T 


(h) 


At  the  limit  of  endurance  the  whole  resistance  will  be  equal 
to  the  whole  rupturing  effort,  or 

Ttr'^p  =.  27tr^  S Nap.  Log.  ^ (13) 

hence,  p — Nap.  Log.  ^ (i) 

289.  As  a special  case,  assume,  as  before,  that  the  wall  of 
the  gun  is  a calibre  in  thickness,  or  R — Zr.  Expression  (i) 
now  becomes 

p = 2S  Nap.  Log.  Z — 28  X 1.09S6 (11) 

or,  in  round  numbers,  p =■  28 (j) 

Comparing  this  with  eq.  (f),  we  see  that  this  gun  would  be 
three  times  as  strong  longitudinally  as  tangentially — if  the  bm-st- 
ing-effort  were  resisted  by  its  tangential  strength  alone. 

The  tangential  and  longitudinal  strains  are  in  directions  at 
right  angles  to  each  other,  and  hence,  probably,  neither  affects 
the  ability  of  the  metal  to  resist  the  other — wliile  the  compres- 
sibility of  the  metal  tends  to  diminish  its  capacity  to  resist 
either. 

290.  Ceushixg-foece. — This  force  diminishes  from  the 
bore  outward,  while  the  area  of  resistance  increases. 

The  effect  of  this  upon  a compressible  truncated  wedge 
would  be  to  change  its  form  from  that  of  Fig.  16  to  that  of 
Fig.  17.  And  the  appearance  of  a cross  section  of  the  gun 
after  rupture  would  be  that  of  Fig.  18.  If  the  metal  were  in- 


THEORY  OF  GUFT  CONSTRUCTION. 


93 


compressible,  the  appearance  of  a 
rupture  would  be  that  of  Fig. 
bore  would  result  from  the 
crushing  of  the  metal ; and  any 
enlargement  caused  by  the  action 
of  a central  force  would  be  ac- 
companied by  an  equal  enlarge- 
ment of  the  exterior  diameter  of 
the  gun ; and  hence  the  strain 
upon  the  metal  at  the  inner  and 
outer  surface  of  the  gun  would 
be  inversely  as  the  radii  of  those 
as  their  squares  (as  in  the  case  of  ( 


cross  section  of  the  gun  after 
, and  no  enlargement  of  the 


Fig.  46.  Fig.  47. 


surfaces  instead  of  inversely 
:ompressible  metal). 


291.  To  find  an  expression  for  the  effect  of  a crushingfiorce. 

Lety>  = the  pressure  per  square  inch  of  gas  on  the  siu’face 
of  the  bore, 

G = the  compression  per  inch  in  length,  due  to  y>,  of  a 
prism  one  square  inch  in  area  of  cross  section, 
r — the  radius  of  the  bore  of  the  gun, 

X = the  radius  of  one  of  the  thin  cylinders  which  com- 
pose the  gun. 

The  elementary  compression  of  any  prism  taken  in  the 
metal  of  the  gun  will  be  = cdx.  If  the  pressure  were  uni- 
form (or  G constant)  throughout  the  length  of  this  prism,  the 
integral  of  this  expression,  or  cx^  would  give  the  entire  compres- 
sion or  increase  in  the  radius  of  the  bore.  But,  in  a gun,  the 
pressure  per  square  inch  against  the  interior  of  each  consecutive, 
elementary  cylinder  of  which  we  may  suppose  it  to  consist,  will 
vary  according  to  some  law  which  must  lirst  be  determined. 

Suppose  a thin,  hollow  cylinder,  and 

let  a = the  tangential  resistance  per  imit  of  length  of 
one  side  of  this  cylinder, 
r'  = its  interior  radius, 

p'  = the  pressure  per  square  inch  against  its  interior 
siu’face  winch  would  just  produce  rupture. 


94 


NAVAL  ORDNANCE  AND  GUNNERY. 


Formula  (cl),  already  obtained  for  tbe  bursting-effort  of  a 
central  force,  gives 

j)'r'  — a,  or  2?'  = ^ (15) 


Or,  tbe  pressure  per  square  inch  against  the  interior  of  a hol- 
low cylinder  necessary  to  develop  a constant  amount  of  tangen- 
tial resistance  in  its  sides,  varies  inversely  as  its  interior  radius. 
It  has  been  shown  that,  at  the  limit  of  endurance. 


P 


- S 


li  — T 

~~IT' 


The  tangential  resistance  developed  in  that  cylinder  of  the 
gun  whose  interior  radius  is  x will  be  equal  to  the  total  tangen- 
tial resistance  of  the  wall  of  the  gun  less  that  developed  in  the 
cylinder  whose  exterior  radius  is  a?,  or  by  eq.  (c). 


Sr 


VR-r 

V R 


Hence  the  pressure  per  square  inch  against  the  interior  sur- 
face of  the  elementary  cylinder,  whose  interior  radius  is  cr,  will 
be 


292.  Supposing  the  compression  per  inch  in  length  of  the 
same  metal  to  be  directly  proportional  to  tbe  pressure  per  square 
inch,  we  shall  have 


p \ G — Sr 


r R — r 


1 

X 


: c 


/ 


where  c'  is  the  compression  per  inch  of  length  due  to  the  force 
p acting  at  the  distance  x from  the  origin.  Solving  the  propor- 
tion with  reference  to  c'. 


, _ Scr  r R — r 1 
^ 2)  \-  R X 


,(16) 


The  expression  for  the  elementary  compression  now  becomes 
du  — c'dx.  Substituting  the  value  of  o'  from  eq.  (16), 


du  = 


Scr  r — r 1 
2)  R X 


Integrating  between  the  limits  R and  r, 


(1‘) 


THEORY  OF  GUN  CONSTRUCTION. 


95 


Scr  r T 


u 


.(k) 


As  before,  in  a special  case,  assume  the  gun  to  be  one  cali- 
bre in  thickness,  or  R = 3r, 


,(18) 


w ^ [i  ^09-  i + I ] 

= Log.  3] (19) 

Jr 


But  the  ITaperian  logarithm  of  3 is  1.0986. 
as  1, 


cr 

¥ 


Assuming  this 


(1) 


293.  Now  supposing^  = 8.,  or  that  the  pressure  per  srpiare 
iuch  on  the  bore  of  the  gun  is  ocpial  to  the  tensile  strength  of 

cv 

the  metal,  we  have  u = -g , or,  the  increase  in  radius  of  the 

bore,  due  to  the  compression  of  the  metal,  in  a gun,  one  calibre 
in  thickness  is  equal  to  one-third  of  the  total  compression  which 
a prism,  whose  height  equals  the  radius  of  the  bore  would 
undergo  under  a pressure  per  square  inch  equal  to  that  against 
the  bore  of  tlie  gun. 

29d.  Now  if  we  suppose  a given  pressm’eto  be  exerted  upon 
the  surface  of  the  bore  of  a gun,  while  its  exterior  diameter  is 
prevented  from  undergoing  any  increment,  the  total  eularg- 
ment  of  the  bore  and  the  consequent  extension  of  the  metal  will 
be  wholly  due  to  comj)ression,  and  all  the  effects  of  compres- 
sion will  be  produced  as  if  the  exterior  of  the  gun  were  uncon- 
strained. 

295.  If  we  now  suppose  the  exterior  restraint  removed,  the 
interior  and  exterior  diameters  would  undergo  precisely  equal 
increments.  Or  the  gun  would  expand  in  the  same  manner  as 
one  of  which  the  metal  is  incompressible,  the  metal  having  al- 
ready undergone  all  the  compression  which  this  pressure  could 
produce,  and  the  extension  of  the  metal  at  the  two  surfaces  of 
the  gun,  which  would  take  place  after  the  removal  of  the  exte- 
rior restraint,  would  therefore  be  inversely  as  their  radii. 

296.  It  has  just  been  shown  that  in  a gun  one  calibre  thick 
the  total  enlargement  of  the  bore  due  to  compression  is  the 
total  extension  of  the  surface  of  the  bore  due  to  this  enlarge- 


96 


NAVAL  ORDNANCE  AND  GUNNERY. 


ment  is  27zr-,  and  tlie  extension  per  inch  of  the  same  surface  is 
o 


0 

2 7T  r S c 
2 7tr  ~‘6' 

If  a he  the  total  extension  per  inch  of  which  the  metal  is 
susceptible,  then  a—x  will  he  the  extension  per  inch  which  the 

O 

surface  of  the  bore  underwent  after  the  removal  of  the  exterior 
restraint,  and  the  extension  per  inch  of  the  exterior  surface  is 


29Y.  To  exemplify : a cylinder  was  taken  the  total  extension 
per  inch  of  which  was  .00303,  the  compression  per  inch  .OOTil, 
one-third  of  which  is  .00117 ; and  .00303  — .00147  =.00156,  one- 
third  of  which  is  .00052,  the  extension  per  inch  of  the  exterior 
of  a gun  one  calibre  thick,  made  of  this  metal,  at  the  moment 
of  interior  rupture. 

But  the  strain  necessary  to  produce  an  extension  of  .00054 
was  found  to  be  11,000  poimds ; hence  the  exterior  of  the  gun 
would  be  under  a strain  of  between  10,000  and  11,000  pounds 
per  square  inch  at  the  moment  of  interior  rupture ; while,  if  the 
metal  were  perfectly  incompressible,  it  would,  at  the  same  mo- 
ment, be  under  a strain  of  18,000  pounds. 

'Z*  0 

298.  The  expression  -x  was  derived  from  the  hypothesis  that 

the  compression  per  inch  of  east-iron  is  directly  proportional  to 
the  pressure.  Experiment  shows  the  compression  of  this  metal 
to  increase  in  a higher  ratio,  so  that  the  effects  of  compressibility 
will  be  even  greater  than  those  just  determined. 

299.  This  example  suffices  to  establish  the  importance  attach- 
ing to  the  property  of  compressibility  in  gun  metal,  its  action 
being  to  prevent  the  full  development  of  both  the  transverse 
and  the  tangential  resistances,  and  to  that  degree  it  is  believed 
(in  guns  of  large  calibre,  and  consequently  of  great  pressure  of 
gas)  as  to  cause  internal  longitudinal  rupture  before  the  trans- 
verse resistance  is  fully  developed,  even  for  the  shortest  practi- 
cable length  of  surface  pressed. 

300.  Transverse  Strain. — In  estimating  the  resistance 
which  a gun  can  offer  to  a tendency  to  transverse  ruptime,  it  will 


THEORY  OF  GUN  CONSTRUCTION. 


97 


be  more  simple  to  regard  it  as  composed  of  staves,  firmly  se- 
cm'ed  at  their  ends,  the  rear  ends  being  supposed  to  be  secured 
to  a central  cylinder ; and,  in  this  case,  it  will  be  only  necessary 
to  consider  a single  stave,  as  all  others  of  equal  width  and  length 
would  be  subjected  to  similar  and  equal  strain. 

301.  Let  us,  therefore,  consider  the  action  upon  a single 
stave,  whose  breadth  is  one  inch.  If  the  gun  be  one  calibre  in 
thickness,  the  exterior  breadth  Avill  be  three  inches. 

We  shall  be  something  below  the  actual  resistance  which 
the  stave  can  offer,  if  we  consider  it  as  of  rectan- 
gular section  of  two  inches  in  breadth ; this  is  ap- 
parent from  inspection  of  Fig.  50, 

Let  the  stave  a be  acted  upon  by  the  pressure 
of  gas  along  its  inner  surface,  and  suppose  the 
pressure  to  be  applied  between  the  points  h and  V. 

Now  this  stave  is  secured  at  both  ends,  and  the  pie.  50. 
rupturing-force  equally  distributed  along  its 
length  between  the  points  of  support.  It  suffers  a tendency  to 


rupture  at  three  points,  as  shown  in  Fig.  51  by  the  lines  be,  o,"' 
c',  b'  c". 

302.  The  formula  for  the  resistance  which  a bar  thus  strained 
can  offer  is 


in  which  w is  the  breaking-weight  distributed  equally  along  the 
bar,  5 the  breadth  of  the  bar,  d its  depth,  I its  length,  and  S'  the 
weight  required  to  break  a bar  of  the  same  material  one  inch 
square,  firmly  secured  at  one  end,  when  applied  at  one  inch 
from  the  point  of  support. 

If  p be  the  pressure  of  gas  per  square  inch,  the  whole  pres- 
sure on  the  stave  be^  and  the  tendency  torujpture  (i.  e.,  the 

7 


98 


NAVAL  OEDNANCE  AND  GUNNERY. 


ratio  of  tlie  bursting-effort  to  the  resistance)  will  be  represented 

7 7. 

pi  pr 

L 

It  thus  appears  that  tbe  tendency  to  transverse  ruptui’e  in- 
creases as  tbe  squ.are  of  the  length  of  the  bore  underpressure, 
and  that  the  resistance  offered  to  this  kind  of  strain  increases  as 
the  square  of  the  thickness  of  metal. 

303.  The  resistance  offered  by  the  transverse  strength  of  the 
staves  acts  in  concert  with  the  tangential  resistance,  and  when 
the  length  of  the  bore  under  pressure  is  such  that  the  increase 
of  its  diameter  due  to  the  bending  of  the  staves that  due  to 
the  compression  of  the  metal  at  the  moment  of  rupture,  shall 
be  equal  to  that  which  it  would  attain  at  the  same  moment  from 
the  action  of  the  tangential  strain  alone,  then  will  the  resistance 
to  rnptiu’e  be  equal  to  the  sum  of  the  transverse  and  tangential 
resistances. 

301.  This  can  only  occur  for  one  particular  length  of  surface 
pressed  and,  for  any  greater  length,  the  staves  would  require 
to  be  bent  out  beyond  the  breaking  diameter  for  the  tangential 
resistance  before  reaching  their  breaking  ti-ansverse  strain ; and 
the  transverse  resistance  would  only  be  equal  to  the  pressure 
necessary  to  bend  the  staves  out  to  the  position  of  tangential  rup- 
ture, mmifsthe  compression  of  the  metal.  Thus  the  tangential 
resistance  would  be  overcome  and  the  gun  split  longitudinally 
before  the  transverse  resistance  would  be  brought  fully  into  action 

305.  The  effect  of  the  crushing  force  on  compressible  metal 
is  to  prevent  the  development  of  the  transverse  resistance  in  the 
same  manner  as  it  did  that  of  the  tangential  resistance : to  di- 
minish the  amoimt  of  aid  Avhich  the  transverse  resistance  can 
bring  to  the  tangential  for  any  greater  length  of  bore. 

306.  When  the  length  of  surface  pressed  becomes  less  than 
that  which  develops  the  joint  action  of  both  resistances,  the 
diameter  due  to  transverse  rupture  will  be  less  than  that  due  to 
tangential  ruj)ture,  and  transverse  rupture  would  first  ensue; 
or,  what  is  more  probable,  in  guns  of  any  considerable  thick- 
ness of  metal,  rupture  Avill  occur  by  splitting  through  the 
breech,  or  by  forcing  the  rear  ends  of  the  staves  outward,  caus- 
ing rupture  along  the  lines  be  and  de  (Fig.  51). 

307.  Eecm-ring  to  the  expression  for  the  tendency  to  trans- 
verse ruptm’e, 

pV 


THEORY  OF  GUN  CONSTRUCTION, 


99 


and  supposing  tlie  transverse  strength  of  iron  to  he  one-fourth 
the  tensile  or  S'  /S,  and  substituting  for  S'  this  value,  vre 
have 

pP 

SSbd^' 


Then  supposing  5 = 2 in.,  c?  = 
tendency  to  transverse  rupture 


10 
2p 


in.,  Z = 20  in.,  we  have  the 


— — ^ or  the  transverse  strength 
o o 


alone,  supposing  the  tensile  strength  to  he  30,000  Ihs.  per  square 
inch,  would  resist  a pressure  of  45,000  lbs.  per  square  inch  for 
two  calibres  in  length  of  a 10-inch  gun,  if  it  could  be  brought 
fully  into  action.  This,  for  reasons  already  given,  cannot,  how- 
ever, be  done;  but  the  transverse  is  doubtless  a powerful 
auxiliary  to  the  tangential  resistance  for  short  lengths  of  bore 
and  where  the  pressure  is  greatest. 

308.  The  Tendencies  to  Rupture  in  Guns  of  One  Calibre 
IN  Thickness,  each  considered  as  independent  of  all  others,  will 
be  as  follows,  viz. : — 

Tangential 

or  rupture  will  ensue  when  3 > 2 /S’. 

Longitudinal , 

I 2i  o 

or  rupture  will  ensue  when  p S. 

Trcmsverse — 

3 b 

or  rupture  will  ensue  when  2 y?  > 3 /S. 


309.  Total  Burstino-  Tendency, — As  already  indicated,  the 
bursting  tendency  is  the  ratio  of  the  bursting  effort  to  the  total 
resistance  which  the  gun  can  offer. 

The  bursting  effort  against  one  side  of  the  gun  is,  from  what 
has  already  been  shown,  eq.  (d),  the  product  of  the  pressure  per 
square  iucb  multiplied  by  the  radius  of  the  bore  and  the  length 
of  the  bore  to  which  pressure  is  applied. 

Let  R be  the  exterior  radius  of  the  gun. 

r “ radius  of  the  bore. 

L “ length  of  the  . bore  to  which  pressure  is 
applied. 

I “ length  of  the  surface  pressed  which  fully 
develops  both  transverse  and  tangential 
resistance. 

pressure  per  square  inch. 


V 


' 100 


NAVAL  ORDNANCE  AND  GUNNERY. 


Let  S be  tbe  tensile  strength  of  the  metal. 

Then  p r L is  the  bursting  effort. 

The  whole  tangential  resistance  will  be  equal  to  that  for  an 
element  of  the  gun  cylinder  one  unit  in  length  multiplied  by 
the  length  of  surface  pressed,  or,  from  eq.  (c). 


LSr 


E — r 
~E~' 


The  foramla  for  the  transverse  resistance  of  a bar  of  rect- 
angular cross  section  is  (Art.  302) 

12  S'  h(P 


310.  By  mechanics  it  is  known  that  the  resistances  which 
bars  of  the  same  material  can  offer  when  the  strain  is  equally 
distributed  along  their  lengths,  and  the  bars  tent  to  their  treah- 
ing  deflection,  are  to  each  other  directly  as  the  fourth  powers  of 
their  length.  But  in  the  case  of  the  staves  forming  a gun 
cylinder,  except  for  short  distances,  tangential  will  ensue  before 
transverse  rupture.  In  order  to  determine,  therefore,  the 
transverse  resistance,  calling  x the  transverse  resistance  due  to 
that  length,  the  following  proportion  may  be  instituted : 


12  S’  tcP 


L 


whence 


: x = r 

12  hcV  V 
^=~7T— 


(20) 


S'  may  be  taken  as  one-fourth  of  the  tensile  strength,  or  - ; 

h is  the  mean  breadth  of  the  stave,  or  — , when  the  inner 

2 r 

breadth  is  one  unit ; d is  the  thickness  of  the  stave,  or  E — r. 

Substituting  these  values,  the  whole  transverse  resistance  of 
a bar  thus  strained  whose  length  is  L,  is 

3 + {E-rYV 

2/-  JJ 

The  total  bursting  tendency  is,  hence, 

C=  — - 


LSr 


E-r  2>  S{E^r){E  -iflr 
E ^rE 

2y?  r’  E L 


2 L Sr'  {E  -r)-\-3  SE  {E  -f  r)  {E  - 


THEORY  OE  GUET  COXSTRUCTIOX. 


101 


'^pr^  R L 

S{R  — r)^r-  L ^ R {R  -{-  r)  {R  — r)^,J..(m) 

311.  DETEKMIIfATION  OF  THE  ExTEEIOE  MoDEL  OF  GuNS. In 

order  that  the  gun  may  be  equally  strong  throughout,  the  bursting 
tendency  must  be  the  same  at  all  points  of  the  bore ; or,  in  other 
words,  for  all  values  of  Z,  G,  in  the  foregoing  paragraph,  must 
be  constant.  Equation  (m)  then  becomes  that  of  a portion  of 
the  curve  of  intersection  of  one  side  of  the  gun  by  a plane  con- 
taining the  axis  of  the  bore. 

In  this  formula,  y?  will  obviously  be  a function  of  Z;  and  if 
we  suppose  the  maximum  pressure  to  be  exerted  upon  a length 
l,oi  the  bore,  and  the  pressure  from  the  forward  extremity  of  V 
to  the  muzzle  to  be  inversely  as  the  volume  occupied  by  the  gas 
(and  hence,  in  this  case,  as  the  length  of  the  bore  thus  occupied), 
then  the  pressure  at  any  distance  Z from  the  bottom  of  the  bore 
should  be  expressed  by 

p'V 

L 


{p'  being  the  maximum  pressiu'e),  and  the  foregoing  forimda 
would  become 


(7=2 


P'tH' 

8 


R 


(7?— r) j^2  G Z -f-  3 i?  (i?  -f-  7*)  (Z  — J • •(if) 
Now  since  2 — is  constant,  the  other  factor  is  constant 


also,  so  that  this  last  expression  need  alone  be  regarded  in  de- 
termining the  relative  values  of  R corresponding  to  the  as- 
sumed values  of  Z. 

312.  From  the  great  excess  of  the  transverse  over  the  tan- 

§ential  resistance  for  the  smaller  values  of  Z,  and  from  the  rapid 
iminution  of  the  transverse  resistance  as  Z increases,  the  value 
of  this  expression,  with  a constant  value  of  Z,  will  first  in- 
crease to  a maximum  and  then  decrease  as  Z increases. 

In  order,  therefore,  to  determine  the  proper  exterior  model 
of  a gun,  we  first  decide  upon  the  volume  of  the  charge ; and, 
from  the  qiiality  of  the  powder,  and  the  form  and  weight  of  the 
projectile,  determine  the  length  of  the  bore  subjected  to  maxi- 
mimi  pi’essure  and  the  value  of  this  pressure. 

313.  We  then  establish  the  relation  betwen  V and  Z,  or  the 
law  of  variation  of  pressure,  and  then  assume  I equal  to  or  a 
little  less  than  two  calibres,  since  experiment  has  shown  the 


102 


NAVAL  ORDNANCE  AND  GUNNERY. 


transverse  resistance  to  be  fuby  developed  for  about  that  length 
of  surface  pressed. 

Then  take  R equal  to  or  a little  less  than  the  greatest  exte- 
rior radius  of  the  gun  and  determine  the  value  of  L that  renders 

R 

{R  - + 3i?  (7?  + r)  (i?  - r)  ^ J (o) 

a maximum.  Then  if  R have  been  assumed  equal  to  the  great- 
est exterior  radius,  the  gun  will  be  cylindrical  from  this  point 
back  to  the  curve  of  the  breech ; and  the  curve  of  that  portion 
forward  of  this  point  will  be  determined  by  assuming  values  for 
L and  determining  for  R such  corresponding  values  as  will 
cause  expression  (o)  to  remain  constant  and  equal  to  its  max- 
imum. 

314.  Illtjsteatiox. — On  account  of  the  influence  of  com- 
pression in  preventing  the  development  of  the  full  strength  of 


the  material,  only  one-third  of  the  theoretical  transverse  resist- 
ance was  used  in  computing  the  exterior  radii  of  the  fifteen- 
inch  gun,  and  the  pressure  was  assumed  to  vary  not  as  L but  as 
V L,  The  formula  used  was 

2y?r^  R v/x 

c = X p rn 

S {R-  r)V2r"-L  -f  R^R  -f  r){R  - (i?) 

The  value  of  R used  in  determining  the  value  of  L which 
rendered  the  bursting  tendency  a maximum  was  22.5  inches. 

The  outer  and  extreme  inner  dotted  lines  in  Fig.  52  give 
the  exterior  form  and  proportions  and  the  diameter  of  the 
bore  of  the  gun  as  cast.  The  curved  dotted  lines  give  the 
form  and  proportions  of  a gun  of  the  same  bore  and  maximum 
exterior  diameter  computed  on  the  hypothesis  that  the  pressure 
of  the  gas  is  inversely  as  the  space  behind  the  projectile  (or  p 
varies  inversely  as  L).  The  middle  dotted  lines  give  the  form 


THEORY  OF  GUY  COYSTRUCTIOY. 


103 


and  proportions  of  a gun  of  tlie  same  diameter  of  bore  and 
maximum  exterior  diameter  on  the  hypothesis  that  the  pressure 
is  inversely  as  the  square  root  of  the  space  behind  the  projectile, 
(or  ])  varies  inversely  as  The  full  lines  show  the  form 

and  proportions  of  this  gun  as  finished. 

315.  It  will  be  observed  that  this  gun  is  heavier  in  the  chase 

than  the  hypothesis  would  make  it.  This  was  done  purposely, 
for  the  reason  that  it  was  intended  to  use  charges  of  such  char- 
acter as  would  produce  a more  uniform  pressm’e  in  the  chase  of 
a gun,  for  a given  maximum  pressure,  than  is  obtained  by  the 
use  of  ordinary  powder.  , 

316.  It  should  be  here  remarked  that  even  for  guns  in  which 
a quick  powder  is  to  be  used,  the  lines  due  to  the  law  that  the 
pressm’e  is  inversely  as  L should  not  be  strictly  adhered  to,  in 
that  part  where  the  most  rapid  diminution  of  exterior  diameter 
occurs ; for  the  reason  that,  in  so  doing,  the  front  ends  of  the 
staves  for  those  lengths  of  bore  subjected  to  the  greatest  press- 
ure would  be  deprived  of  their  proper  support  and  the  trans- 
verse resistance  would  be  greatly  diminished  just  where  it  is 
most  needed,  and  where  its  value  is  gi’eatest  in  a properly  mod- 
elled gun. 

The  beginning  of  the  taper  should  be,  therefore,  say  half  a 
calibre  farther  forward  and  the  taper  less  rapid  than  the  loss  of 
pressure  in  this  part  of  the  gun  would  make  it. 

317.  Experiment  has  not  yet  satisfactorily  established  the 
law  of  variation  in  pressure  due  to  the  ordinarj’  cannon  powder. 
But  it  is  thought  that  no  powder  is  fit  for  use  in  guns  of  large 
calibre  that  will  not  so  far  approximate  to  uniformity  of  press- 
ure as  to  conform  to  the  law  that  the  pressm’e  is  inversely  as 

VT> 

318.  PREPOl^DEIlAlSrCE. — Defistitioys. — The  moment 
of  a solid  with  reference  to  a plane  is  equal  to  the  product  of  the 
weight  of  the  solid  multiplied  by  the  pei’pendicular  distance  of 
its  centre  of  gravity  from  the  plane. 

If  moments  tending  to  produce  rotation  with  the  hands  of  a 
watch  are  considered  positive,  evidently  those  tending  to  pro- 
duce rotation  against  the  hands  of  a watch  are  'negative. 

The  preponderance  of  a gun  is  the  moment  of  the  weight  of 
the  gun  about  the  axis  of  the  trunnions  divided  by  the  distance 
between  the  axis  of  the  trunnions  and  the  centre  of  the  elevat- 
ing-screw-hole. It  is  the  pressure  in  pounds  on  the  screw  when 
the  gun  is  level. 

319.  To  DETEEinsTE  THE  Peepondeeance. — It  is  thus  seen 
that  the  weight  of  the  gun  and  its  moment  about  the  axis  of  the 
trunnions  must  be  determined. 


104 


NAVAL  OKDNANCE  AND  GUNNEET. 


As  tlie  measurements  in  guns  are  made  from  the  base-ring, 
it  will  be  convenient  to  take  its  plane  for  tbe  plane  of  reference. 
Having  obtained  tbe  moment  of  tbe  weight  of  tbe  gu7i  with  ref- 
erence to  this  plane,  to  deduce  that  about  tbe  axis  of  tbe  trun- 
nions involves  but  a simple  transformation. 

The  gun  being  assmned  homogeneous,  the  weights  of  its 
parts  are  proportional  to  their  volumes.  Tlie  latter  can  there- 
fore be  used  in  tbe  calculation,  and  only  changed  into  weights 
at  the  last  step. 


In  the  accompanying  figure  (Ho.  53),  let  A,  B,  C,  and 
D be  the  positions  of  the  elevating-screw-hole,  the  plane  of  the 
base-ring,  the  centre  of  gravity  of  the  gun,  and  the  axis  of  the 
trunnions  respectively  ; P,  the  preponderance  acting  at  the  ele- 
vating-screw-hole, and  W,  the  weight  of  the  gun  acting  at  the 
centre  of  gravity. 

By  the  principle  of  the  lever,  the  moments  of  these  forces 
must  be  equal ; or 

P X AD  = "W  X CD 


Letting  AB  = h,  BD  = a,  and  BC=a? 
P X (a  + &)  — TV  X {a  — x), 

. • . P TVa  — Wa?. 

Since  TV  ; by  substitution, 

Ya  — \x 


P = 


a -[-h 


-d,. 


.(a) 


TVhere  Y is  the  volume  of  the  gun  in  cubic  inches. 

Yx,  the  moment  of  the  volume  of  the  gun  with  refer- 
ence to  the  plane  of  the  base-ring. 
a,  the  distance  of  the  axis  of  the  trunnions  from  the 
plane  of  the  base-ring. 


THEORY  OP  GUY  CONSTRUCTIOY. 


105 


5,  tlie  distance  of  the  centre  of  tlie  elevating-screw- 
hole  from  the  plane  of  the  base-ring. 
d,  the  weight  of  a cubic  inch  of  the  gnn-metah 

320.  The  volume  of  the  gan  is  obviously  the  sum  of  the 
volumes  of  the  parts  of  the  gun,  regarded  as  solid,  diminished 
by  the  sum  of  the  volumes  of  all  its  cavities. 

From  Mechanics,  it  is  known  that  the  moment  of  a solid 
with  reference  to  a plane  is  equal  to  the  algebraical  sum  of 
the  moments' of  its  parts  Avith  reference  to  the  same  plane. 

In  applying  this  principle  to  the  case  of  preponderance,  the 
following  smnmary  may  he  taken  as  a guide  ; subject,  of  course, 
to  such  modification  as  the  form  of  the  particular  gun  considered 
necessitates. 

The  portion  of  the  gun  forward  of  the  base-ring  is  divided 
into  parts  whose  volumes  and  moments  can  be  computed,  the 
gun  being  considered  solid.  Generally  speaking,  the  gun  may 
be  divided  into  a cylinder,  a solid  of  revolution  having  an  odd 
number  of  equidistant  sections,  and  therefore  coming  under 
“ Simpson’s  Rule,”  and  one  or  more  frustums  of  a cone. 

These  moments  and  those  of  the  trunnion  and  rim-bases 
are  expressed  and  marked  'positive. 

The  moments  of  the  bore  and  chamber  are  expressed  and 
marked  negative. 

In  rear  of  the  base-ring  are  the  breech  and  cascabel,  whose 
moments  are  expressed  and  marked  negative. 

Should  there  be  any  cavities  here  Avhose  moments  need  be 
considered,  these  are  expressed  and  positive. 

This  distinction  of  signs  flows  from  the  definition  of  positive 
and  negative  moments. 

Since  Yx  = sum  of  the  moments, 

sum  of  the  moments  . 

^ sum  of  the  volumes 

321.  The  formula  is  Avritten  in  this  manner  merely  to  saAm 
space.  The  division  indicated  in  the  second  member  is  not  per- 
formed, as  the  terms  of  the  fraction,  and  not  its  value.,  are 
sought. 

The  moments  are  collected  and  placed  in  the  numerator  with 
their  appropriate  signs ; the  denominator  being  similarly  made 
up  of  tlie  Amlumes. 

Factors  common  to  the  two  tenns  are  then  taken  out,  and 
written  before  the  algebraical  sum  of  the  residting  quotients — 
and,  in  turn,  such  of  these  quotients  as  contain  common  factors 
are  combined  into  one.  By  thoroughly  carrying  out  the  princi- 


lOG 


NAVAL  ORDNANCE  AND  GUNNERY. 


pie  of  factoring  and  combination,  much  time  and  labor  may  be 
saved  in  comj)nting. 

The  indicated  additions  in  the  numerator  and  denominator 
are  performed,  and  the  results  used  in  the  expression  for  the 
preponderance. 

It  must  be  borne  in  mind  that  we  have  assumed  the  metal 
to  be  homogeneous,  though  in  practice,  the  breech  is  more  dense 
than  the  chase,  owing  to  the  mode  of  casting ; hence,  the  pre- 
ponderance, as  calculated,  is  always  somewhat  less  than  in  reality. 

This  excess  of  weight,  in  rear  of  the  trunnions,  is  reduced  to 
a minimum  to  allow  the  breech  to  be  easily  elevated  or 
depressed.  It  is  practically  impossible  to  place  the  trunnions  so 
that  there  shall  be  no  preponderance ; nor  has  it  been  deemed 
advisable  to  dispense  with  it  entirely  in  ISTavy  guns,  as  the 
weight  of  the  projectile  in  loading  would  depress  the  muzzle, 
and  even  when  home,  the  breech  would  not  readily  follow  down 
the  screw  for  elevation. 

Example. 


322.  The  form  and  dimensions  of  a XY-inch  gun  being 
given  in  the  accompanying  diagram  (Fig.  51)  and  table,  to  com- 
pute its  preponderance. 


Dimensions. 


Weight 

in 

Pounds. 

Lexgtii  rx  rxcHES  of 

AC 

AD 

AE 

AF 

AG 

AE 

AN 

AT 

AU 

AL 

AM 

AO 

AP 

42,000 

25 

35 

37.5 

45 

55 

65 

75 

85 

95 

14G 

24 

.3 

31 

THEORY  OF  GUN  CONSTRUCTION. 


107 


Diameter^  in  inches,  at 


r 

A 

C 

D 

F 

G 

H 

K 

T 

U 

L 

0 

P 

48 

48 

47.8 

45 

39.8 

36.2 

33.2 

30.8 

29.0 

21.0 

12.0 

12.0 

Trunnions.  Bore  and  Chamber. 


Lengtli. 

Span  of 
Rim-bases. 

• Diameter  at 

Length  of 

Diameter 

at 

QR 

QS 

Q 

R 

ac 

ab 

b 

c 

5.5 

48 

12 

12 

146 

15 

15 

15 

Taking  tlie  moments  of  the  parts  of  the  gnn  with  reference 
to  the  plane  of  the  base-ring,  due  regard  being  had  to  the  signs, 
gives  ecpiation  (1)  [from  formula  (b)]. 

323.  a.  Volume  of  cylinder  = nrh  = tt  X X 35. 

Its  centre  of  gravity  is  distant  or  17.5  from  its  base.  Its 

moment,  therefore,  is  x 24*  X 17.5  X35. 

324.  b.  By  Simpson’s  Rule,  the  moment  of  the  solid  DY 
with  reference  to  the  plane  of  its  first  section  is  equal  to 

d 

-f  44%  -f  2^3*3  + Vh^x,  + Th,x^  + Vh^e^  + h,x^, 
and  its  volume  is  equal  to 

+ 4/q  -[-  2/^3  -[-  4A^  -(-  2A3  -}-  4Aj  -|-  hi), 

the  A’s  being  the  areas  of  the  sections,  the  a?’s  their  distances 
respectively  from  the  first  section,  and  d,  the  common  interval. 
Substituting  the  numerical  values  of  these  quantities,  the  expres- 
sion for  the  moment  becomes 

-V"-^(23.9*  X 0 -f  4 X 22.5*  X 10  + 2 X 19.9*  x 20  + 4 X 18.1* 
X 30  + 2 X 16.6*  X 40  + 4 X 15.4*  X 50  + 14.5*  X 60), 
and  that  for  the  volume 


108 


NAVAL  ORDNANCE  AND  GUNNERY. 


i3f-<23.9"  + 4 X 22.5“+  2 X 19.9“  + 4 X 18.1“+ 2 X 1C.6“  + 
4 X 15.4“  + 14.5“), 

which  reduce  to  -+7T  x 157,495.4  and  -+/T  X 6,408.7. 

Dividing  the  moment  by  the  volume  gives  the  distance  of 
the  centre  of  gi-avity  of  the  solid  from  the  first  section,  equal 
to  24.58.  Hence  tlie  moment  of  the  solid  with  reference  to  the 
j)lane  of  the  base-ring  is 

-+;r  X 6,408.7(35  + 24.58)  ==  KJ>-7t  X 6,408.7  X 59.58. 

325.  c.  Volume  of  a frustrum  = + Rr  + r“), 


and  its  centre  of  gravity  is  distant  from  its  larger  base 
h ^“  + 2^r+  3r“ 

4 + /tV  + ?'“  ’ 


where  A is  the  altitude  of  the  frustrum,  R and  t the  radii  of  the 
larger  and  smaller  bases  respectively;  hence  the  moment  of  the 
frustrum  with  reference  to  the  base-ring  is  equal  to 


I X 51(14.5“  + 14.5  X 10.5  + 10.5“)  X (o5  + + X 
14.5“  + 2 X 14.5  X 10.5  + 3 X 10.5 


14.5“  + 14.5  X 10.5  + 10.5“ 


17/T  X 55,691.3, 


and  ^ts  volume  177t  x 472.7. 

526.  d.  The  trunnions  are  cylinders  whose  volumes  are 
7T  X X A = 7T  X 6“  X 5.5,  and  their  centres  of  gravity  are 
distant  from  the  base-ring  37.5.  Their  moment  is  2/T  X 6“  X 
5.5  X 37.5. 

327.  e.  The  rim-bases  are  sections  of  cylinders  by  cones. 
Tlie  expressions  for  tlieir  volumes  and  the  positions  of  their  cen- 
tres of  gravity  are  integrals  of  such  complicated  forms,  that,  in 
practice,  the  rim-bases  are  taken  as'cylinders;  on  account  of  their 
small  volume  and  their  proximity  to  the  centre  of  gravity  of  the 
gun,  the  error  introduced  through  this  assumption  is  so  small  as 
to  1)0  inappreciable. 

Volume  of  each  rim-base  = X 7.5“  X .75. 

Moment  of  both  rim-bases  ~ tt  x 7.5“  X -75  X 37.5. 


328. +  The  breech  is  a hemisphere  whose  volume  h 

and  moment  with  reference  to  the  plane  of  the  base  is  |-r  x d 
X or  X 24“  ==  2r  X 2-4“  X 8,  and  -|r  X 24“  X |-  X 24 
— Ir  X 24“  X 8 X 9,  respectively. 

329.  g.  The  cascabel  is  taken  as  a cylinder  whose  height  is 


THEORY  OF  GUX  CONSTRUCTION. 


109 


T,  and  its  radius  5.  Its  volume^  therefore,  is  tt  X 5“  X I,  and 
its  moment  tt  x 5^  X 1(2-1  3.5)  = X 5’  X I X 27.5. 

330.  h.  The  metal  of  the  juncture  of  the  cascahel  with  the 
hreech  may  he  assumed,  in  practice,  to  compensate  that  taken 
from  the  screw-hole  ; both  are  neglected. 

331.  {.  The  hore  is  a cylinder  whose  height  is  131,  its  radius 

7.5.  Its  volume,  therefore,  is  tt  x 7.5^  X 131,  and  its  moment 
7t  X 7.5^  X 131(15  G5.5)  =:  ;r  X 7.5^  X 80.5  X 131. 

332.  j.  The  chamber  is  taken  as  a paraboloid  of  revolution 
whose  height  is  15,  and  radius  7.5.  Its  volume,  being  half  that 
of  the  circumscribing  cylinder,  is  7t7.5’“  X 7.5.  Its  centre  of 
gravity  is  distant  its  height  from  the  vertex.  Its  moment, 
therefore,  is  tt  x 7.5''‘  X 7.5  X 10. 

333.  Substituting  these  numerical  expressions  in  equation  (1) 
gives  equEttion  (2). 

(See  page  110  for  equations.) 

331.  To  Determine  the  Position  of  the  Trunnions. — In 
designing  a gun,  the  preponderance  is  decided  upon  beforehand, 
thus  giving  rise  to  the  inverse  problem,  “ For  a desired  pre- 
ponderance, where  should  the  trunnions  be  placed  ? ” 

The  weights  and  moments  of  the  trunnions  and  rim-bases 
are  neglected,  as  being  at  the  axis  about  wliich  the  gun  rotates, 
these  cannot  perceptilny  affect  the  result.  The  remaining  vol- 
umes and  moments  are  obtained  as  before. 

Eeferring  to  equation  (a)  (Art.  319),  P is  now  known,  and 
BD  = a becomes  the  unknown  cpiantity  to  be  determined. 
Solving  this  equation  with  reference  to  a gives  equation  (c). 


Ph  V xd 
^ Yd-P  ' 


(e) 


For  convenience  P may  be  assumed  equal  to  Qd.  With 
this  substitution  and  the  cancelling  of  d in  numerator  and 
denominator 


_ Qb  Vx 
V-Q 


(d) 


Example. 

335.  In  the  XV-inch  gun  already  computed,  where  should 
the  trunnions  be  placed  that  the  gun  may  have  a preponderance 
of  1,781  lbs.  ? 

Here  Q = ^ 6,861.51,  h = 28,  Vx  = 5,980,271.2, 

and  V = 162,087.7. 


110 


NAVAL  ORDNANCE  AND  GUNNERY. 


2'^ 

+ 


I 


ci;?o 

+ 


+ 


II  'd 


PIS 


ol 


I + 


S II 


wo  wow  ^ o 


II  II  II  II 


w So 


L'  O o 


, I 

o w 


II  II  II 


w o'  j 

* j a 

II 


E » r; 


GENERAL  DESCRIPTION  OF  ORDNANCE. 


Ill 


Substituting  these  numerical  values  in  e'^^uation  (d),  and 
solving, 

_ 6861.54x  28  + 5980271.2  _ 6172394.3  _ on 

162087.7  — 6861.54  “ 155226.2  ~ ' 

Hence  the  axis  of  the  trunnions  must  he  placed  at  the  dis- 
tance of  39.76  inches  from  the  base-ring  in  order  that  the  gun 
may  bear  the  desired  preponderance. 

336.  To  Deteemint3  the  Effect  on  the  Peepondeeance  of 
A Change  in  the  Position  of  the  Tehnnions. 

Different  values  of  P are  taken,  and  the  coiTesponding  val- 
ues of  a computed.  P and  a are  assumed  to  vary  proportion- 
ally, and  the  variation  in  pounds  of  P for  a change  of  a tenth 
of  an  inch  of  a thus  obtained. 

This  assumption  is  not  absolutely  true,  but  nearly  enough 
so  for  all  practical  purposes. 

Example. — Had  we  taken  780  lbs.  for  the  desired  prepon- 
derance of  the  'KY4nch  gun,  a would  have  been  found  equal  to 
38.12. 

Hence  changiug  the  position  of  the  axis  of  the  trunnions  by 
1.64  inches,  has  caused  the  preponderance  to  vary  by  1004  lbs. 
— or  61.2  lbs.  for  each  tenth  of  an  inch. 


CHAPTER  III. 


CAST  GTTXS. 

Section  I. — Standard  of  Iron. 

337.  Smelting  of  Iron  for  C^vnnon.^ — It  is  in  tlie  smelt- 
ing furnace  that  the  character  of  the  iron  is  fixed.  Iron  of 
good  chai-acter  and  high  susceptilhlitj  may  he  spoiled  by  its 
treatment  at  the  foundry ; but  this,  ivith  ordinary  experience 
and  intelligence,  ought  rarely  to  occur. 

It  is  impi’acticable,  with  our  present  knowledge,  to  make 
good  and  reliable  guns  from  iron  that  leaves  the  smelting-fur- 
nace with  bad  qualities. 

338.  The  smelting  of  iron  is  a purely  chemical  process,  and 
should  be  conducted  with  the  same  regularity  and  precision  as 
any  other  important  chemical  process.  There  are  so  many  dis- 
turbing causes  tending  to  affect  its  character  and  qualities,  that, 
after  every  precaution  shall  have  been  taken  to  remove  them, 
perfect  uniformity  in  the  quality  of  the  iron  produced  from  day 
to  day  cannot  be  effected,  yet  a near  approximation  to  uniform- 
ity is  practicable. 

339.  All  the  stock  for  a “blast”  of  gun-iron  should  be 
carefully  prepared  and  housed  before  beginning  to  “ blow.” 
The  ore  should  all  be  i-oasted  and  well  mixed  so  as  to  be  as 
nearly  uniform,  as  to  size  of  lumps  and  all  other  qualities,  as 
possible. 

The  charcoal  should  all  be  made  as  nearly  as  possible  from 
the  same  kind  of  wood,  of  the  same  uniformity  as  to  quality, 
and  well  mixed  together  after  charring.  All  the  stock  shoulcl 

CD  O 

be  carefully  weighed  and  supplied  to  the  furnace  at  regular  in- 
tervals of  time. 

310.  The  pressure,  temperature,  and  hygrometrical  condition 
of  the  “ blast,”  should  be  kept  as  nearly  constant  as  possible. 
The  temperature  of  the  blast  may  be  kept  very  nearly  constant 
without  usmg  what  is  termed  a “ hot-blast,”  by  warming  it 
just  enough  to  bring  it  above  the  highest  summer  temperature. 


* Rodman. 


CAST  GUNS. 


113 


341.  The  quantity  of  moisture  may,  it  is  believed,  be  kept 
neai-ly  constant  by  passing  the  blast  some  distance  over  water 
heated  to  the  proper  temperature.  And  this  may  be  readily 
done  by  passing  the  blast  through  a long  horizontal  tube,  like  a 
cylindrical  steam-boiler,  partly  tilled  with  water,  and  kept  at  a 
constant  temperature  by  the  waste  heat  from  the  furnace. 

The  temperature  of  the  water  should  be  such  as  to  saturate 
the  blast  with  moisture,  and  thus  render  it  hygrometrically  inde- 
pendent of  atmospheric  changes. 

342.  Piling  the  Pigs. — Supposing  a standard  of  quality  to 
have  been  determined  (Art.  374),  with  the  stock  all  prepared 
for  a given  number  of  guns,  and  having  determined  by  com- 
parison with  the  standard  the  quality  of  iron  required,  a fur- 
ther approximation  to  identity  in  quality  of  the  metal  in  the 
guns  may  be  made  by  casting  each  run  of  metal  from  the 
smelting-furnace  into  a number  of  pigs  of  equal  size,  some- 
thing greater  than  the  number  of  the  guns  to  be  made,  and 
piling  them  in  separate  piles — each  run  of  metal  furnishing 
one  pig  to  each  pile. 

343.  Each  pile  should  contain  metal  enough  for  one  gun 
and  one  test-cylinder ; and  be  kept  separate  and  distinct  from 
all  others  in  transportation,  and  be  repiled  in  the  foundry-yard 
in  the  same  order  as  at  the  smelting-furnace : one  gun  being 
made  from  each  pile,  after  the  treatment  which  the  iron  should 
receive  at  the  foundry  shall  have  been  determined  by  experi-  - 
ments  made  on  the  iron  in  the  surplus  piles.  The  pigs  should 
be  cast  in  molds  as  prepared  from  a pattern,  so  as  to  be  smooth 
and  free  from  adhering  sand  as  possible. 

344.  Diffeeence  in  Quality. — The  difference  between 
iron  as  it  exists  when  presented  for  use  in  “ pigs  ” and  when  in 
the  body  of  the  finished  gun  is  very  great,  sometimes  amount- 
ing to  a difference  in  density  of  more  than  20  pounds  per  cubic 
foot,  and  in  tenacity  more  than  as  1 to  2. 

This  serves  to  show  how  unreliable  the  tests  of  the  first  fu- 
sion pig-iron  are,  as  means  for  determining  the  quality  of  iron 
and  its  suitableness  for  making  cannon. 

345.  The  quality  of  cannon  may  be  improved  by  endeavor- 
ing to  ascertain  the  different  qualities  of  the  metal  used  in 
making  them,  and  the  best  methods  of  treating  it  in  the  pro- 
cesses of  melting,  casting,  and  cooling. 

346.  It  is  found  that  some  kinds  of  iron  are  susceptible  of 
very  great  improvement,  by  different  methods  of  treatment  at 
the  foundries  ; while  other  kinds  are  at  their  maximum  strength 
in  the  crude  pigs.  The  cause  of  this  difference  in  the  suscepti- 
bility for  change  and  improvement  will  doubtless  be  found  in 

8 


114 


NAVAL  ORDNANCE  AND  GUNNERY. 


the  qualities  of  ores  used,  and  in  the  processes  of  smelting 
them. 

347.  The  following  table  enables  us  to  compare  the  various 
cpialities  of  cast-iron  and  bronze,  and  see  the  variations  which 
occur  in  each. 


VARIOUS  QUALITIES  OF  CANNON  METALS.* 


Trans- 

COMPRES- 

Metals. 

DEKSITY. 

Tenacity. 

VEKSE 

SITE 

Hardness. 

Strenoth. 

STRENGTn. 

Cast-iron..  • 

Least . . . 
Greatest 

6,900 

7,400 

9.000 

45,970 

5,000 

11,500 

84,529 

174.120 

4 57 
33.51 

Wrought- 

Least. . . 

7,704 

38,027 

6,500 

40,000 

10.45 

iron 

Greatest 

7,858 

74.592 

127,720 

12.14 

Bronze • 

Least. . . 

7,978 

17,698 



4.57 

Greatest 

8,953 

56,786 

.... 

5.94 

Cast-steel . ■ 

Least. . . 

7,729 

198,944 

Greatest 

7,862 

128,66o 

23,000 

391,985 

.... 

A prominent  feature  of  this  table  is  that  which  shows  the 
gi-eat  difference  between  the  lower  and  higher  grades  of  the 
same  metal.  In  cast-iron  the  density  differs  as  0.9  to  7.4,  a 
..  difference  equal  to  31  pounds  per  cubic  foot ; in  tenacity  it  dif- 
fers as  45,970  to  9,000  pounds  per  square  inch,  or  as  5 to  1,  and 
in  hardness  as  7 to  1.  The  bronze  varies  iii  tenacity  from 
56,786  to  17,698,  more  than  3 to  1,  and  in  density  it  is  as  8.953 
to  7.978,  equal  to  61  pounds  in  the  cubic  foot. 

348.  Effects  of  different  Treatment. — Usually  the 
quality  of  iron  is  greatly  modified  and  improved  by  remelting 
and  long  continuance  in  fusion.  But  all  lands  of  iron  are  not 
affected  in  like  manner  by  these  processes. 

In  examining  the  effects  of  the  different  treatment  of  iron 
at  the  foundry,  such  samples  should  be  chosen  as  will  best  ex- 
hibit the  following  particulars  and  characteristics,  viz. ; 

1st.  Tlie  properties  which  distinguish  the  different  gi’ades 
of  iron  made  from  the  same  ores  at  the  same  furnace. 

2d.  The  changes  in  the  mechanical  properties  of  iron  pro- 
duced by  repeated  meltings  of  one  of  these  grades,  separately, 
showing  the  changes  effected  at  each  melting. 

3d.  "The  changes  produced  by  repeated  meltings  of  the  dif- 
ferent irrades  of  iron  and  of  different  fusions  mixed. 

o 


Reports  of  Experimeuts  on  Metals  for  Cannon. — U.  S.  Ordnance  Dept. 


CAST  GUNS. 


115 


Itli.  The  changes  produced  in  iron  of  the  same  melting  and 
quality,  by  casting  it  into  masses  of  different  bulk,  and  by  dif- 
ferent methods  of  cooling. 

319.  The  softest  kinds  of  iron  will  endure  a greater  num- 
ber of  meltings  with  advantage  than  the  higher  grades.  It  ap- 
pears from  Major  Wade’s  experiments  with  Greenwood  iron 
that  when  it  is  in  its  best  condition  for  casting  into  proof-bars 
of  small  hulk,  it  is  then  in  a state  which  requires  an  additional 
fusion  to  bring  it  up  to  its  best  condition  for  casting  into  the 
massive  bulk  of  cannon.* 

In  selecting  and  preparing  iron  for  cannon,  we  may  proceed 
by  repeated  fusion,  or  by  varying  the  proportions  of  the  differ- 
ent grades  and  different  fusions,  until  the  maximum  tenacity  is 
attained. 

350.  Vakiation  of  Density  and  Tenacity. — An  increase 
of  density  is  a consequence  which  invariably  follows  the  rapid 
cooling  of  cast-iron,  and  as  a general  rule,  the  tenacity  is  in- 
creased by  the  same  means.  The  density  and  tenacity  usually 
vary  in  the  same  order.  It  appears  that  the  tenacity  generally 
increases  quite  uniformly  with  the  density,  until  the  latter  as- 
cends to  some  given  point;  after  which  an  increased  density  is 
accompanied  by  a diminished  tenacity. 

The  turning-point  of  density  at  which  the  best  qualities  of 
gun-iron  attain  their  maximum  tenacity  appears  to  be  about 
7.30.  At  this  point  of  density,  or  near  it,  whether  in  proof- 
bars  or  in  gun-heads,  the  tenacity  is  greatest. 

As  the  density  of  iron  is  increased  its  liquidity  when  melted 
is  diminished.  This  causes  it  to  congeal  cpickly,  and  to  form 
cavities  in  the  interior  of  the  casting. 

351.  If  in  pi-eparing  iron  for  guns  it  is  carried  too  Jiig\ 
either  by  long  continuance  in  fusion  or  by  using  a large  portion 
of  a hard  grade  of  iron,  the  casting  will  be  lost. 

High  Iron. — The  condition  of  the  iron  at  casting  is  said  to 
be  too  high,  when  the  process  of  decarbonization  has  been  car- 
ried too  far  ; and  the  result  will  be  a very  hard  iron. 

352.  Pkactical  Tkeatment  in  Fusion. — In  the  practical 
treatment  of  iron  in  fusion  while  preparing  it  for  casting  into 
cannon,  it  may  be  safely  continued  in  fusion,  with  increasing 
improvement  of  its  quality,  so  long  as  sufficient  liquidity  is 
retained  to  insure  an  exemption  from  cavities  in  the  interior  of 
the  casting. 

The  point  at  which  such  cavities  of  a fatal  character  will 
form,  will  be  reached  before  arriving  at  the  point  of  density 
for  maximum  tenacity. 

* Eeports  of  Experiments  on  Metals  for  Cannon  ; 1856. 


116 


NAVAL  OEDNANCE  AlID  GUNNERY. 


353.  Tests  while  in  Fusion. — A convenient  method  for 
determining  the  condition  of  the  iron  while  in  fusion,  and 
whether  it  has  arrived  at  the  proper  condition  for  casting,  or 
should  be  longer  continued  in  fusion,  is  found,  in  dipping  from 
the  melted  pool  of  iron  and  easting  into  small  bars  about  10 
inches  long  and  from  1 to  2 inches  square  at  one  end,  and 
tapering  to  a point  at  the  other  end.  The  first  one  is  taken 
from  the  furnace  and  cast  soon  after  the  iron  is  all  melted,  and 
others  are  cast  at  such  intervals  afterwards  as  may  be  judged 
proper.  They  are  cast  vertically,  point  downwards,  in  sand- 
molds,  and  cooled  rapidly. 

351:.  Great  care  must  be  taken  in  the  preparation  of  the 
molds  for  these  samples,  as  upon  sample-bars  so  small,  even  a 
little,  more  or  less  moisture  of  the  sand  of  the  molds  will  make 
a difference  as  to  the  rate  of  progress  towards  white  iron. 

355.  As  samples  cannot  be  obtained  from  the  heads  of 
large  guns  (Art.  367)  until  several  days  after  they  are  cast, 
separate  proof-bars  are  made  and  tested,  to  aid  in  directing  the 
progress  of  the  work.  This  enables  the  founder  to  determine 
the  relative  quality  of  the  iron  soon  after  it  is  cast,  and  in  the 
intervals  between  each  successive  daily  casting. 

356.  The  proof-bars  are  broken  in  different  places,  and  the 
condition  of  the  iron  is  judged  by  the  appearance  of  the  several 
fractures. 

These  fractures  will  exhibit  various  aspects,  from  white  at 
the  small  end  to  dark  gray  at  the  large  end ; and  the  bars  at 
the  latter  periods  of  the  fusion  will  exhibit  the  white  at  a 
greater  distance  from  the  small  end,  and  the  mottle,  bright,  and 
lighter  shades  will  be  found  adv’ancing  towards  the  large  end. 
This  method,  although  much  less  reliable  than  that  of  an 
actual  measure  of  density  and  strength,  is  convenient,  because 
of  its  ready  application  at  short  intervals,  while  the  iron  is  in 
fusion ; and  a practical  eye  will  soon  be  able  to  mark  the  prog- 
ress of  the  changing  quality  of  the  non,  and  to  determine  the 
proper  time  for  casting  the  gun. 

357.  ORYSTALLIZATIOA. — Of  the  various  circumstances 
which  affect  the  strength  of  cannon-metal,  the  most  important 
appear  to  be  those  which  connect  themselves  with  crystalliza- 
tion. 

General  Law. — It  is  a law  of  the  molecular  aggregation  of 
crystalline  solids,  that  when  their  particles  consolidate  under 
the  iniluence  of  heat  in  motion,  their  crystals  arrange  and 
group  themselves  with  their  principal  axis  in  lines  pei'pendicu- 
lar  to  the  cooling  or  heating  surfaces  of  the  solid;  that  is,  in 
the  lines  of  direction  of  the  heat-wave  in  motion,  which  is  the 


CAST  Ginsrs. 


117 


direction  of  least  pre:snre  within  the  mass ; and  this  is  true, 
whether  in  the  ease  of  heat  passing;  from  a previously  fused 
solid  in  the  act  of  cooling  and  crystallizing  on  consolidation,  or 
of  a solid  not  having  a crystalline  structure,  hut  capable  of 
assuming  one  upon  its  temperature  being  sufficiently  raised,  by 
heat  applied  to  its  external  surfaces,  and  so  passing  into  it."" 

35y.  Moleculak  Constitution  of  C.vnnon  Metals. — The 
metals  used  in  gun  construction  are  crystallizing  bodies,  which 
in  consolidating  obey  more  or  less  perfectly,  according  to  their 
conditions,  this  law;  so  that  in  castings  of  these  metals,  the 
planes  of  crystallization  group  themselves  perpendicularly  to 
the  surfaces  of  external  contour;  that  is,  in  the  directions  in 
which  the  heat  of  the  fluid  metal  has  passed  outwards  from 
the  body  in  cooling  and  solidifying.  Because  the  crystals  of 
these  metals  are  always  small  and  are  never  very  well  pro- 
nounced, these  directions  are  seldom  very  apparent  to  the  eye, 
but  they  are  not  the  less  real. 

359.  Development  of  Ceystals. — Their  development  de- 
pends upon ; 

First.  The  character  of  the  metal  itself ; all  irons  that  pre- 
sent a coarse,  large-grained,  dark,  or  spangled  fracture,  contain 
a large  proportion  of  uncombined  carbon  or  graphite,  and  form 
in  castings  of  equal  size  the  largest  crystals. 

Second.  The  size  or  mass  of  the  castings — -the  largest  cast- 
ings presenting  for  any  given  variety  of  metal  the  largest  and 
coarsest  aggregation  of  crystals;  but  by  no  means  the  most 
regular  arrangement  of  them,  which  depends  chiefly  upon — 

Third.  The  rate  at  which  the  mass  of  the  casting  has 
cooled,  and  the  regularity  with  which  heat  has  been  carried  off 
by  conduction  from  its  surfaces  to  that  of  the  mold  adjacent  to 
them. 

360.  Chilled  Castings. — Those  castings  in  which  the 
fluid  iron  is  poured  into  a nearly  cold  and  very  thick  mold  of 
cast-iron,  whose  high  conducting  power  rapidly  carries  off  the 
heat,  present  the  most  complete  and  perfect  development  of 
the  crystalline  structure  perpendicular  to  the  chilled  surfaces 
of  the  casting.  In  such,  crystals  are  often  found  penetrating 
more  than  an  inch  into  the  substance  of  the  metal,  clear  and 
well-defined. 

361.  Illustrations. — These  prevailing  directions  of  crystal- 
line arrangement  may  be  made  more  clear  to  the  eye  by  the  ac- 
companying Figure  55,  which  shows  sections  of  a round  and  a 
square  bar  of  cast-iron  where  the  crystallization  is  well  devel- 


* Mallet. 


118 


NAVAL  ORDNANCE  AND  GLDTNERT. 


oped.  In  the  round  bar  the  crystals  all  radiate  from  the  cen- 
tre ; in  the  square  bar  they  are  arranged  perpendicularly  to  the 
four  sides,  and  hence  have  four  lines  in  the  diagonals  of  the 


Fig.  55. 

square — in  which  the  terminal  planes  of  the  crystals  abut  or 
interlock,  and  about  which  the  crystallization  is  always  con- 
fused and  irregular. 

The  result  of  this  arrangement  is  to  create  planes  of  weak- 
ness where  the  difierent  systems  of  crystals  intersect. 

362.  Effect  of  Ckystallization  on  Stuength. — The  size 
and  arrangement  of  the  crystals  of  a metal  have  an  important 
influence  on  its  strength.  This  arises  from  the  fact  that  the 
adhesion  of  the  crystals  by  the  contact  of  their  faces  is  less 
than  the  cohesion  of  the  particles  of  the  crystals  themselves, 
and  that  consequently  rupture  takes  place  along  the  larger  or 
principal  crystalline  faces. 

A metal  will  therefore  be  strongest  where  its  crystals  are 
small. 

363.  Size  of  Crystals. — The  size  of  the  crystals  of  a par- 
ticular metal  depends  on  the  rate  of  cooling  of  the  heated 
mass;  the  most  rapid  cooling  giving  the  smallest  crystals. 
The  size  of  the  crystals  or  coarseness  of  grain  in  castings  of 
iron  depends,  for  any  given  make  of  iron  and  given  mass  of 
castings,  upon — 

First.  The  high  temperature  of  the  fluid  iron  above  that 
just  necessary  to  its  fusion,  which  influences — 

Second.  The  time  that  the  molten  mass  takes  to  cool  down 
and  assume  again  the  solid  state. 

The  lower  the  temperature  at  which  the  fluid  iron  is  poured 
into  the  mold,  and  the  more  rapidly  the  mass  can  be  cooled 
down  to  solidiflcation,  the  closer  will  be  the  grain  of  the 
metal,  the  smaller  its  crystals,  the  fewer  and  least  injurious  the 
planes  of  weakness,  and  the  greater  the  speciflc  gravity  of  the 
castings. 

Slow  cooling  develops  a coarse,  uneven  grain,  with  large 
but  thoroughly  irregiflar  aud  confused  crystallization  ; cast-ii’on 


CAST  GUNS. 


119 


with  such  a grain  is  never  strong  or  cohesive,  though  soft  and 
extensible. 

361.  The  more  rapidly  a casting  once  consolidated  can  be 
cooled,  without  introducing  injurious  effects,  the  finer,  closer, 
and  more  even  will  be  its  grain  on  fracture,  and  with  any  given 
metal  the  greater  will  be  its  strength.  The  rate  of  cooling 
cannot  be  accelerated  beyond  a moderate  limit.  If  this  limit 
be  exceeded,  as  by  casting  in  a cold,  thick,  highly  conducting 
metallic  mold,  the  iron  is  “ chilled,”  its  constitution  changed, 
and  the  carbon,  not  having  time  to  crystallize  out,  remains  com- 
bined or  diffused  through  the  mass. 

It  cannot  be  so  fast  as  to  endanger  unequal  contraction,  nor 
must  it  be  so  fast  in  large  castings,  such  as  guns  requiring  to 
be  “ fed,”  from  a feeding  or  sinking-head,  with  fresh  portions 
of  hot  fluid  metal  during  consolidation  to  All  up  the  internal 
cavities  or  porosity  due  to  contraction  and  crystallization,  that 
this  feeding  cannot  be  accomplished. 

The  larger  the  mass  of  the  casting,  with  any  given  quality 
of  iron,  generally  the  coarser  is  the  grain ; that  is,  the  larger 
are  the  crystals  that  develop  themselves  in  the  mass. 

The  same  metal  that  shall  produce  a fracture  bright  gray, 
mottled,  and  without  a crystal  visible,  in  a small  bar,  will  in  a 
large  casting  produce  a dark,  confusedly  crystalline  surface  of 
fracture  as  coarse  as  granite  rock. 

365.  Contkactiojst  of  Castings. — A certain  amount  of  con- 
traction, on  becoming  solid  from  the  liquid  state,  occurs  in  all 
castings.  For  iron  this  is  variable,  and  depends  upon  the  mass 
of  the  castings;  being  greatest  for  small  and  least  for  large 
castings,  of  the  same  make  of  iron,  and  poured  at  the  same 
temperature. 

There  are  two  conditions  that  principally  affect  the  degree 
of  contraction,  namely,  the  extent  to  which  the  fluid  metal  as 
entering  the  mold  has  been  expanded  by  elevation  of  tempera- 
ture, and  the  state  of  final  aggregation  of  the  particles,  depend- 
ing upon  the  size  of  the  mass. 

366.  Effect  of  Sudden  Change  of  Form  in  Castings. — 
Sudden  changes  of  form  or  of  dimensions  in  the  parts  of  cast- 
guns,  besides  the  injury  they  do  to  the  crystalline  structure  of 
the  mass,  introduce  violent  strains,  due  to  the  unequal  contrac- 
tion of  the  adjoining  parts,  whose  final  contraction  has  been 
difiierent. 

For  this  reason,  in  the  method  of  easting  heavy  guns  as 
adopted  in  Sweden,  it  is  considered  necessary  to  form  the  ex- 
terior of  the  casting  as  a perfect  cylinder. 

367.  Time  REQumED  for  Cooling  Castings. — The  enormous 


120 


KAVAL  ORDXAN-CE  AXD  GTJXXERT. 


time  required  by  a lar^e  casting  for  cooling  is  not  generally 
known.  A solid  casting  sufficiently  large  for  a XV-indi  gen 
weighs  about  35  tons ; it  is  reddiot  three  days  after  having  been 
east,  and  only  becomes  cold  enough  to  handle  after  affiortnight. 
The  cooling  of  a casting  must  be  uniform,  so  far  as  uniformity 
is  possible.  This  is  impossible  strictly  in  any  easting;  the 
approach  to  it  is  most  difficult  in  heaA'y  solid  castings,  and 
hence  the  great  advantage  of  the  practice  of  hollow  casting 
upon  a suitably  made  core,  admitting  of  internal  cooling  by 
artificial  means. 

368.  Effects  of  Ieeegelve  Cooling  of  Castings. — The 
contraction  of  cast-iron  in  becoming  solid  introduces  strains  into 
the  mass  by  consolidation  of  one  portion  of  the  casting  before 
another.  When  a large  gun  is  east  solid  and  the  metal  cools 
in  the  ordinary  way,  the  external  portions  solidify  long  before 
the  interior  has  ceased  to  be  liquid,  and  the  process  of  solidifica- 
tion is  propagated  as  it  were,  in  parallel  layers  from  the  outside 
to  the  centre  of  the  mass.  When  the  first  layer  or  thickness  of 
solid  crust  has  formed  in  the  exterior,  it  forms  a complete  arch 
all  round,  so  that  the  contraction  between  fiuidityand  solidifica- 
tion of  each  subsequent  layer  is  accommodated  by  portions  of 
matter  withdrawn  radially  from  the  interior  towards  the  still 
cooling  exterior ; that  is  to  say,  from  a smaller  towards  a larger 
circumference. 

369.  The  final  effect  of  this,  propagated  to  the  centre  of 
the  mass,  is  two-fold. 

First.  To  produce  a violent  state  of  internal  tension  in  the 
particles  of  the  metal  in  radial  lines  from  the  axis  of  the  gnu 
inwai'd  as  a cylinder,  tending  to  tear  away  the  external  portions 
of  the  mass  from  the  internal  nucleus. 

Second.  To  produce  about  the  centre  or  along  the  axis  a 
line  of  weakness,  and  one  in  which  the  texture  of  the  metal  is 
soft,  porous,  and  of  extremely  low  specific  gravity. 

370.  The  effect  of  this  unequal  contraction  may  be  so  great 
as  to  crack  the  interior  metal  of  cast-iron  cannon,  even  before  it 
has  been  subjected  to  the  force  of  gunpowder,  and  large  masses 
of  iron  which  have  been  cooled  very  rapidly  by  casting  them  in 
iron  molds,  have  been  known  to  split  open  longitudinally,  from 
no  other  cause  than  the  enormous  strains  to  which  they  are 
thus  subjected. 

371.  Sinking-head. — Guns  have  long  been  cast  in  a verti- 
cal position  and  with  a certain  amount  of  head  of  metal  above 
the  topmost  part  of  the  gun  itself.  From  this  head  the  casting 
is  fed  with  fresh  portions  of  fluid  metal  during  consolidation  ; 
it  also  affords  a gathering-place  for  all  scoria  or  other  foreign 


CAST  GUN'S. 


121 


matter.  But  tlie  great  value  of  increased  Lead  of  metal  is  in 
adding  to  the  density  of  castings,  and  so  also  to  tlieir  strength. 
Fineness  of  grain,  smallness  of  crystal,  density,  increased  cohe- 
sion and  elasticity,  are  all  induced  by  casting  under  lai-gely  in- 
creased statical  heads  of  fluid  metal.  By  appa^-atus  not  difficult 
to  contrive,  atmospheric  pressure  or  that  of  condensed  air 
might  easily  be  brought  to  aid  that  of  the  head  of  metal,  with 
economy  in  reducing  the  labor  and  cost  of  the  mass  of  metal 
to  be  melted,  and  with  the  advantage  of  enabling  the  pressure 
on  the  solidifying  mass  to  be  varied. 

372.  Effect  of  Age  on  Endukance. — The  length  of  time 
that  a piece  has  been  cast  influences  its  endurance.  A gradual 
adjustment  takes  places  of  the  internal  strains  produced  in 
cooling,  and  like  many  other  substances  iron  possesses  the 
property  of  accommodating  itself  to  an  unnatural  position,  and 
Anally  of  adopting  this  as  its  natural  one. 

373.  Impeovement  en  Castings.- — The  principal  improve- 
ment in  the  fabrication  of  cast-iron  guns,  is  Captain  Eodman’s 
process  of  cooling  them  as  far  as  possible  from  the  interior, 
and  for  this  purpose  casting  them  hollow. 

The  design  is  to  .remedy  the  various  defects  of  the  old 
process;  principally  to  obviate  the  tendency  of  solid  castings 
to  burst  by  their  own  initial  strains,  by  reversing  the  process  of 
cooling  and  shrinking  described  above.  Since  there  would  then 
be  no  force  opposed  to  the  contraction  of  the  inner  layers  of 
metal,  except  the  trifling  cohesion  of  tlie  liquid  or  pasty  mass 
that  they  shrink  away  from,  they  would  not  be  left  in  tension, 
and  therefore  they  could  not  exert  any  power  to  pull  the  ex- 
terior layers  into  compression. 

The  method  employed  is,  to  carry  off  the  internal  heat  by 
passing  a stream  of  water  through  a hollow  core,  inserted  in 
the  centre  of  the  mold-cavity  before  casting,  and  to  surround 
the  flask  with  a mass  of  burning  coals  to  prevent  too  rapid 
radiation  from  the  exterior.  (Art.  M5.) 

Extensive  trials  have  l?een  made  to  test  the  merits  of  this 
plan,  and  the  results  show  that  cast-iron  cannon  made  by  it 
are  not  only  stronger  but  are  less  liable  to  enlargement  of  the 
bore  from  continual  firing,  the  surface  of  the  bore  being  the 
hardest  and  densest  part  of  the  casting,  and  best  calculated 
to  resist  pressure  and  abrasion.- 

374.  STANDARD  OF  QUALITY. — Before  proceeding  to 
execute  a contract  for  cannon,  a trial-gun  should  be  made  and  ex- 
posed to  extreme  proof  with  service  charges.  After  undergoing 
this  proof  in  a satisfactoiy  manner,  the  trial-gun  should  serve  as 
a standard,  and  the  proportions  of  the  several  kinds  of  metal 


122 


NAVAL  ORDNANCE  AND  GUNNERY. 


used,  and  the  methods  employed  in  its  manufacture  should  be 
followed  in  all  respects  in  the  fabrication  of  other  guns.  With 
the  trial-gun  should  be  cast  a samjple-gun  or  a cylinder  of  equal 
diameter,  and  at  least  half  the  length  of  the  gun,  from  which 
test  specimens  should  be  cut  and  tested. 

375.  The  sample-gun  or  cylinder  should  be  of  the  same 
diameter  as  the  guns  to  be  made,  and  should  be  made  under 
the  same  cii’cumstances  which  are  to  attend  the  preparation  of 
the  iron  for,  and  the  casting  and  cooling  of,  the  guns  themselves. 

The  object  of  the  sample  is  to  obtain  specimens  which  have 
not  been  subjected  to  previous  strain  and  vibration,  as  would 
be  the  case  if  taken  from  the  fragments  of  the  broken  trial- 
gun. 

For  it  is  impossible  to  reason  back  to  what  would  have  been 
either  the  capacity  for  work  or  the  work  due  to  elasticity  of  an 
unstrained  specimen  by  knowing  to  what  extent  these  proper- 
ties were  possessed  by  that  specimen  after  it  had  been  sub- 
jected to  both  strains  and  vibrations  of  unknown  intensity  and 
number. 

And  although  it  is  interesting  to  know  to  what  extent  these 
properties  are  possessed  by  the  fragments  of  a worn-out  gun, 
yet  it  would  be  of  far  greater  practical  utility  and  importance 
to  know  the  value  of  these  properties  in  the  new  untried  guns. 

Specimens  thus  obtained  would  afford  reliable  results ; and 
in  connection  with  the  powder-proof  with  service-charges  of 
guns,  cast  at  the  same  heat,  these  results  would  become  stand- 
ards with  which  to  compare  other  lots  of  iron  or  other  guns, 
and  thus  determine  beforehand  the  number  of  rounds  which  a 
gun  will  stand. 

376.  Comparison  with  Standard. — "While  the  cannon  are 
making,  the  inspecting  officer  examines  and  tests  the  metal  be- 
fore it  is  used,  witnesses  its  melting  and  casting,  and  tests  the 
metal  in  the  first  gun  made,  before  the  second  one  is  cast.  If 
the  first  proves  unsatisfactory,  such  changes  are  made,  either  in 
the  material  or  in  its  treatment,  as  will  tend  to  produce  the 
desired  result. 

This  practice  of  ascertaining  the  quality  of  the  material 
used,  and  of  the  casting  made  from  day  to  day,  as  the  work 
proceeds,  enables  the  founder  to  distinguish  the  material,  to 
select  those  of  best  quality,  and  to  treat  them  in  the  best 
manner. 

If  these  tests  are  satisfactory,  the  inspecting  officer  is  assured 
of  the  good  quality  of  the  guns,  before  any  proof  by  firing  is 
made.  And  this  supersedes  the  necessity  of  using  excessive 
proof-charges  in  the  final  proof,  which  may  do  serious  and  even 


CAST  GUNS. 


123 


fatal  injury  to  guns,  witliout  bursting  them  or  leaving  any  vis- 
ible marks  of  the  injury. 

• 377.  Means,  of  Comparison. — The  testing-instrument  (Art. 

396)  furnishes  to  the  founder  a convenient  and  accurate  method 
of  comparing  the  qualities  of  iron.  It  therefore  enables  him 
to  select  his  materials  before  casting,  with  greater  certainty  and 
safety.  lie  can  also  by  this  means  determine  the  comparative 
utility  of  different  methods  of  melting  and  casting  the  gun. 
As  the  quality  of  the  iron  is  essentially  changed  by  the  different 
ways  of  treating  it  while  in  the  melted  state,  and  by  the  differ- 
ent means  adopted  for  cooling  it  after  it  is  cast  into  the  mould, 
the  testing-instrument  enables  one  to  ascertain  the  effect  pro- 
duced by  these  processes  in  all  their  several  stages  of  progress, 
and  to  decide  upon  that  which  is  found  most  suitable  for  mak- 
ing the  guns  of  the  best  quality. 

378.  Contract  with  Founder. — The  metal  of  guns  made 
for  the  naval  service  is  subjected  to  tests  to  ascertain  its  hard- 
ness, specific  gravity,  and  tensile  strength. 

The  particular  hardness,  density,  and  strength  which  the 
metal  must  possess  is  specified  m the  special  contracts  with  the 
Founder. 

Each  foundry  keeps  an  accurate  record  of  the  character, 
mixture,  and  mode  of  working  the  metal  of  each  gun,  so  that 
its  foundry  number  will  at  once  refer  to  its  class,  date,  weight, 
etc. 

379.  Samples. — The  quality  of  the  iron  as  it  exists  in  the 
gun  is  more  accurately  represented  by  samples  taken  from  its 
sinJdng-liead  than  by  any  which  can  be  obtained  from  other 
parts  of  the  casting  without  injury  to  the  gun.  These  samples 
are  taken  from  the  lower  end  of  the  sinking-head,  next  to  the 
muzzle  of  the  gun,  and  are  cut  out  so  that  their  axes  will  be 
parallel  to  the  axis  of  the  casting,  at  a distance  from  the  centre 
of  the  head  equal  to  the  distance  between  the  axis  of  the  bore 
and  the  middle  of  the  metal  in  the  wall  of  the  piece  when 
bored. 

When  guns  burst  from  extreme  proof,  samples  are  taken 
from  different  parts  to  test  the  strength  of  the  metal.  The 
radial  specimens  are  generally  found  to  be  somewhat  stronger 
than  the  longitudinal  from  the  same  cross-section  of  the  gun. 
(Art.  362.) 

380.  Marking-samples. — The  sinking-head  and  the  gun 
to  which  it  belongs  have  the  same  foundry-number. 

The  samples  have  the  foundry-numbers  and  the  letter  II 
stamped  upon  both  ends  of  them. 

All  samples  taken  from  any  gun-easting,  whether  from  the 


124 


NAVAL  ORDNANCE  AND  GUNNERY. 


sinking-lieacl,  the  proof-bars,  or  other  casting,  from  the  same 
melting,  bear  the  founchy-nnmber  of  the  gun.  The  letter  II, 
added  to  the  number,  denotes  that  the  sample  is  taken  from 
the  head.  OH  denotes  a sample  from  near  the  outer  or  ex- 
terior surface.  Ill  an  inner  sample,  and  other  letters  are  used 
denoting  the  locality  from  which  the  specimen  has  been  taken. 
The  letter  B on  any  sample,  denotes  that  it  was  taken  from  a 
proof-bar.  The  figures  which  follow  the  letter  indicate  the 
fusion  or  the  number  of  times  the  iron  has  been  melted. 

381.  Value  oe  Tests. — The  samples  are  tested  as  soon  as 
practicable.  The  tests  are  carefully  made  and  recorded  Avith 
the  other  proofs  and  inspections,  and  afford  the  means  of  com- 
parison betAveen  the  metal  of  different  guns  and  of  different 
foundries. 

Ho  particular  Amlue  is  attached  to  these  tests  as  an  indication 
of  the  absolute  endurance  of  the  gun,  but  only  as  exhibiting 
the  similarity  that  the  several  guns  bear  to  the  standard.  Ex- 
perience has  shown  that  a variation  of  about  2,000  pounds 
more  or  less,  in  the  tensile  strength,  is  a sufficient  limit  to  be 
allowed,  and  within  Avhich  to  confine  the  founders ; an  exact 
adherence  being  impossible. 

382.  Staetdaed  Specimen. — In  order  to  obtain  a suitable 

sample  for  de- 
termining the 
density  and 
strength  ; a cy- 
lindrical piece 
about  four  inches 
long  and  tivo  in- 
ches in  diameter 
is  taken,  and  pre- 
pared by  reduc- 
ing it  to  a form 
that  will  fit  the 
holders  of  the 
testing  - machine 
(Fig.  56),  and 
of  such  bulk  as 
will  be  conveni- 
ent for  ascertaining  its  density.  In  order  to  obtain  reliable 
comparatiA'e  results,  it  is  necessary  that  tlie  specimens  shall  all 
conform  to  the  standard  in  size  and  shape. 

383:  To  Determine  the  Density. — The  sample  is  weighed 
in  air  and  in  pure  distilled  AA'ater ; clear  rain  or  river  water  may  be 
substituted,  if  its  relative  density  be  first  accurately  determined. 


Fig.  56. 


CAST  GUN'S. 


125 


In  taking  the  speeihc  gravity  of  iron,  the  operations  are  nn- 
avoidably  performed  with  water  at  different  temperatures, 
varying  with  the  state  of  the  weather  at  the  time ; and  as  the 
density  of  the  water  varies  with  its  temperatui’e,  it  is  necessary 
to  note  the  temperature  of  the  water  at  the  time  of  w^eighing 
tlie  sample,  and  to  reduce  the  ascertained  density  to  what  it 
would  have  been  if  the  sample  had  been  weighed  in  water  at 
the  temperature  of  the  assumed  unit. 

A thermometer  is  suspended  in 
the  water,  and  its  temperature  is 
noted  at  each  weighing.  The 
temperatiu’e  of  60°  F.  is  taken  as 
the  standard  ; and  when  a sample 
is  weighed  in  ^Yater  of  any  other 
temperature,  the  weight  of  water 
displaced  by  it  is  corrected  by  the 
table  compiled  for  that  purpose. 

The  instruments  employed  for 
determining  the  density  of  speci- 
mens are — The  Hydrometer  and 
the  Densimeter^  or  Balance  for 
specific  gravities. 

384.  The  Hydkometek. — Fig, 

57  exhibits  the  form  of  the  instru- 
ment. The  bulb  B is  of  thin  cop- 
per about  7 inches  diameter  at 
top,  and  8 inches  high,  having  a 
brass  handle,  II,  and  a solid  stem 
of  brass,  S,  screwed  into  the  bot- 
tom. 

A vertical  index-stem  made  of 
steel,  I,  is  inserted  in  the  upper 
part  of  the  handle.  The  upper 
end  of  this  stem  receives  the 
weight-pan,  W,  which  is  sup- 
ported in  its  place  by  a conical 
socket  on  its  under  side. 

The  height  of  the  hydrometer, 
from  the  bottom  of  the  ball  to  the 
weight-pan,  is  21  inches.  Its  gen- 
eral form  and  the  distribution  of 
the  metal  within  it,  place  the  centres  of  gravity  and  buoyancy 
so  far  apart  that  it  readily  takes  a vertical  position,  when  im- 
mersed, and  will  deviate  very  little  from  it,  however  irregularly 
it  may  be  loaded. 


Fig.  57. 


126 


NAVAL  ORDNANCE  AND  GUNNERY. 


Its  maximum  buoyancy  is  about  14,000  grains ; but  this 
may  be  reduced  when  weighing  lighter  samples,  by  adding  at 
the  bottom  one  or  more  adjusting-weights,  which  may  vary  it 
one-half. 

The  index-stem  is  of  very  small  diameter,  a length  of  one 
inch  displacing  one  grain  of  water. 

The  zero-mark  is  in  the  middle  of  the  length  of  the  stem. 

The  weights  are  marked  in  grains,  decimally  divided,  vary- 
ing from  one-tenth  of  a grain  to  4,000  grains. 

The  vessel  which  contains  the  water  is  a glass  jar  about  a 
foot  in  diameter  and  two  feet  in  height.  It  must  be  placed  on 
a level  support,  and  the  height  of  the  water  in  the  jar  should 
be  such  that  when  the  hydrometer  descends  to  the  bottom, 
the  weight-pan  shall  still  be  above  the  sm-face  of  the  water. 

The  weight-pan  is  attached  to  the  index-stem  by  an  open 
socket,  so  that  it  may  be  removed  with  its  load,  and  placed  on 
a table,  where  the  weights  may  be  more  safely  and  accurately 
counted. 

385.  To  DETEKinxE  the  Density  of  Watek. — The  hy- 
drometer may  be  employed  to  determine  the  relative  density 
of  distilled  and  any  other  kind  of  Avater.  The  weight  of  the 
hydrometer,  added  to  its  balance-weight  in  distilled  Avater,  at 
the  temperature  of  60°,  gives  the  weight  of  a quantity  of  pure 
standard  Avater,  Avhich  is  equal  in  bulk  to  the  immersed  part  of 
the  instrument.  The  Aveight  of  the  liA-drometer  and  its  load 
when  immersed  in  like  manner,  in  other  kind  of  Avater  at  the 
salne  temperature,  gix’es  the  weight  of  an  equal  bulk  of  the  lat- 
ter, and  this  Aveight  divided  by  the  former,  gives  the  multiplier 
for  correcting  the  density,  Avhen  ascertained  in  any  other  than 
pure  distilled  water. 

At  the  foundries  generally,  river-water  is  found  to  be  suf- 
ficiently pure  for  use  Avithout  needing  any  correction. 

386.  To  Use  the  Instedjient. — First  load  the  pan  with 
grain  Aveights  until  the  instrument  rests  at  its  zero,  and  record 
the  sum  of  these  weights,  as  the  halance  of  the  hydrometer. 
Next,  place  in  the  pan  the  samples  together  Avith  as  many 
weights  as  Avill  again  bring  the  instrument  to  its  zero,  and  re- 
cord these  Aveights,  as  the  sample  balance  in  air.  The  differ- 
ence betAveen  these  balances  is  equal  to  the  Aveight  of  the  sam- 
ple in  air.  Then  place  the  sample  on  the  bulb  of  the  instru- 
ment at  P,  and  immerse  both  until  the  hydi’ometer  again  rests 
at  zero,  and  record  the  weights  on  the  pan,  as  the  sample  bal- 
ance in  water.  The  difference  between  this  balance  and  that 
in  air  is  equal  to  the  weight  of  the  water  displaced  by  the 
immersed  sample.  The  temperature  of  the  Avater  at  the  time 


CAST  GUN’S. 


127 


of  weighing  is  rioted,  and  if  it  is  not  at  60°,  divide  the  weight 
displaced  by  sample,  by  that  number  in  the  table  which  is  op- 
posite the  noted  temperature,  and  the  quotient  will  give  the 
corrected  displacement  for  the  temperature  of  60°.  Then,  the 
weight  of  the  sample  in  air  divided  by  the  corrected  displace- 
ment gives  the  density  of  the  sample. 

387.  Example. 


Sample  No.  4,  H.  Grains. 

Balance  of  the  hydrometer 11485.0 

Balance  with  sample  in  air 923.0 


Difference  = weight  of  sample  in  air 10562.0 


Balance  with  sample  in  water 2370.4 

Balance  with  sample  in  air 923,0 


Difference  = weight  of  water  displaced 

Noted  temperature,  72^°. 

Tabular  number,  72J  = .998912. 

1447.4 

--na  .n-io  “ 1449.0  coi’rected  displacement, 
, 10562 

==  7.289  = density. 

1449 

Or  by  Logaritlims — 


Water  displaced  at  72J°  =:  1447.4.. 
Tabular  number  for  72J°  = .998912, 


1447.4 


Logarithms. 

3.1605886 

1.9995274 


Logarithm  of  corrected  displacement 


3.1610612 


Weight  of  sample  in  air  = 10562 4.0237461 

Corrected  displacement 3.1610612 

Density  = 7.289  = 0.8626849 


The  determination  of  densities  by  the  hydrometer  requires 
much  practice  to  arrive  at  correct  results,  and  is,  moreover,  very 
tedious. 

The  densimeter^  or  halance^  may  therefore  be  advantageously 
substituted  for  it,  the  results  being  occasionally  checked  by  the 
hydrometer. 


128 


NAVAL  ORDNANCE  AND  GUNNERY, 


388.  The  Densimetee,'-’'  or  Balan-oe  for  Specific  Gravities, 
is  in  principle  a simple  beam  scale  of  accurate  workmanship.  As 
made  by  W urdemann,  it  consists  of  an  open  beam  of  German 
silver,  A (Fig.  58),  fitted  Avitb  knife-edge  bearings,  and  mounted 


Fig.  58. 


in  a hollow  standard,  B.  The  central  knife-edge,  (7,  upon  which 
the  beam  is  balanced  is  l.d  inch  long,  and  those  at  extremities, 
d,  from  Avhich  the  scale-pans  are  suspended  are  0.9  in.  long ; all 
bearing  their  lengths  on  steel  plates. 

When  not  in  use  the  beam  rests  on  its  Y’s,  e e,  on  a cross- 
bar, F,  at  the  top  of  the  standard. 

This  cross-bar  also  supports  the  scale-pans  on  separate  rests, 
(j  y,  free  from  contact  Avitli  their  knife-edges. 

Through  the  standard  a rod  passes  for  lifting  the  beam 
Avhen  in  use  ; it  connects  v’itli  the  crank,  h. 

The  standard  is  set  on  a brass  plate  furnished  ivith  a circu- 
hir  spirit-level  and  foot-screws,  o o,  for  accurately  levelling  it. 


Inspection  and  Proof  of  Cannon — U.  S.  Navy. 


CAST  GUNS. 


129 


The  whole  apparatus  is  enclosed  in  a glass  case  to  protect  it 
from  dust  or  currents  of  air;  the  case  is  fitted  with  a sliding 
front  which  is  counterpoised  for  convenient  manipulation. 

3S9.  When  not  in  use  the  glass  case  should  be  kept  closed  to 
protect  the  balance  from  dust,  and  a vessel  containing  crystalized 
chloride  of  calcium^  to  absorb  the  moisture  of  the  air,  ought 
to  be  always  placed  inside  the  case. 

The  best  arrangement  for  this  pirrpose  is  a glass  funnel, 
containing  the  chloride  set  in  a beaker-glass.  The  beaker 
should  always  be  emptied  before  the  water  reaches  the  end  of 
the  funnel-stem. 

390.  Ad.justments. — The  heam  is  balanced  by  two  adjust- 
ments placed  above  it. 

First,  by  the  horizontal  screws,  Avith  milled  heads,  for 
the  zero  of  the  index  below  r,  and,  second,  by  the  lai'ge  nut,  s, 
on  the  pei-pendicular  sereAV  for  vertical  balance.  Thi^  last, 
when  once  set,  it  is  seldom  necessary  to  touch. 

391.  The  Arms  are  adjusted  to  equal  length.  There  is  to 
each  knife-edge  end  a steel  screAv  with  capstan-head,  which  when 
screwed  forward  will  spring  out  the  part  upon  which  the  kiiifc- 
edge  rests,  and  thus  lengthen  its  distance  from  the  centre. 
Both  ends  are  made  tlius  adjustable,  by  which  means  perfect 
symmetry  of  the  trvo  parts  of  the  beam  is  obtained  and  the  ne- 
cessity of  screwing  back  during  the  adjustment  is  obruated, 
since  it  will  merely  be  necessary  to  lengthen  the  arm  Avhich 
proves  to  be  shortest. 

To  test  this  the  relative  place  of  the  scales  should  be 
changed  after  first  balancing  them  exactly,  if,  after  the  change 
either  preponderates,  it  proves  that  arm  to  be  the  longest.  One 
half  the  difference  is  to  be  corrected  with  weights,  and  the 
other  half  Avith  the  adjusting-screws.  Great  caution  must, 
hoAvever,  be  observed  in  not  screwing  up  too  much  at  a time. 

A correct  result  in  weighing  may  be  obtained  Avithout  this 
adjustment  being  absolutely  exact,  by  fii’st  balancing  the  speci- 
men to  be  weighed,  with  any  coiiA^enient  substance,  then  re- 
moving the  specimen  and  substituting  in  its  place  knoAvn 
Aveights  until  equilibrium  with  the  counterpoise  is  restored. 

392.  Use  of  the  IxsTEUiiExx. — By  the  crank,  K,  placed  in 
front  of  the  case,  the  centre  bearing  is  gently  raised,  which, 
lifting  the  beam  off  its  Y’s,  also  takes  up  the  scales. 

Y hen  the  beam  is  completely  raised  the  oscillations  of  the 
scales  are  arrested  by  touching  the  spring-lever,  Y,  on  the  right 
of  the  crank,  which  works  the  steadying-pins,  w w,  under  each 
pan. 

On  abandoning  the  lever  the  preponderance  of  the  specimen 

9 


ISO 


NAVAL  ORDNANCE  AND  GUNNERY. 


or  tlie  -weiglit,  will  immediately  be  manifested,  and  additional 
weights  may  be  added  or  removed  iintil  they  are  in.  equilibrium. 

When  placing  the  specimen  and  estimated  counterbalancing 
weights  in  the  scales,  the  beam  should  always  be  let  down  on 
the  siipports ; but  small  weights  may  be  added  or  changed  whilst 
simply  arresting  the  scales  with  the  lever. 

The  door  should  not  be  pushed  up  higher  than  is  just  neces- 
sary to  obtain  convenient  access,  as  the  balance  is  very  sensitive. 
Care  should  be  taken  not  to  abrade  the  pans  by  carelessly  put- 
ting in  the  specimens  or  rubbing  to  remove  dust. 

393.  Detekjiination  of  Specific  Gkatitt. — For  the  deter- 
mination of  specific  gravities  a German-silver  vessel  is  used  just 
large  enough  to  conveniently  hold  the  specimen,  and  open  at 
the  top,  which  is  planed  off  perfectly  straight  so  that  a plate- 
glass  provided  for  the  purpose  can  be  slid  over  it,  and  will  shut 
air-tic^t.  This  vessel  is  filled  with  distilled  water,  carefully  re- 
moving air-bubbles  from  inside  the  vessel,  or  drops  mechani- 
cally adhering  to  the  outside. 

Weight  and  temperature  are  noted,  and  a table  may  be 
computed,  so  that  tliis  element  constitutes  for  the  instrument 
used  a constant. 

It  will  be  convenient  to  keep  the  water  in  a reservoir  of 
considerable  size,  to  avoid  the  inconvenience  of  frequent 
changes  of  temperature. 

The  absolute  weight  of  the  specimen  having  been  previ- 
ously taken  and  noted,  it  is  then  submerged  in  the  vessel,  a 
small  pair  of  tongs  being  used  for  the  purpose,  when  it  will  dis- 
place a quantity  of  water  equal  to  its  volume.  The  vessel  is 
again  covered  with  the  plate-glass,  using  the  same  precautions 
as  before,  and  the  weight  taken. 

39T.  Since  specific  gravity  is  represented  by  the  ratio  of  the 
absolute  weights  of  the  same  volume  of  water,  and  of  the  article 
to  be  determined,  we  have  to  divide  the  weight  of  specimen 
by  a quantity  obtained,  by  deducting  the  wei_^t  of  the  vessel, 
with  specimen  inserted,  from  the  sum  of  weight  of  vessel  filled 
with  water,  and  of  the  weight  of  specimen. 

Therefore  if  — 

C— Weight  of  vessel  filled  with  water  (constant), 

W= Absolute  weight  of  specimen, 

W,= Weight  of  vessel  with  specimen  submerged, 

S = Specific  gravity. 

We  have 


Grains. 

CAST  GUNS. 
Example. 

Logarithms. 

c = 

8618.5 

w = 

9888.0 

3.9951085 

■ c + w = 

18506.5 

17137.7 

c + W - w,  = 

1368.8 

3.1363400 

s = 

7.223 

. 0.8587685 

395.  Fokm  of  Recokd  of  Comptjtatioit. 


By  Densimeter. 


Calibre. 

No. 

Spec. 

Tem. 

Weight. 

Grains. 

Grains. 

Tem. 

Logarithms.  |sp.  Gr. 

IX-in. 

1910. 

H.I. 

63° 

Tank  filled 

Spec,  in  air. .... 

Spec,  in  water . . 
Water  disijlaced . 

8963.1 

9845.5 

18807.6 

17465.0 

1343.6 

63° 

1.9999020 

3.9932378 

3.9931398 

3.1279466 

.8651932 

7.332 

IX-in. 

1910. 

H.I. 

63° 

Water  displaced. 

8962.1 

9787.2 

18749.3 

17416.5 

1332.8 

63° 

f.  9999020 
3.9906585 

3.9905605 

3.1247650 

.8657955 

7.343 

132 


NAVAL  ORDNANCE  AND  GUNNERY. 


By  IIydeo^ietee. 


Calibre. 

No. 

1 

Spec.jTem. 

■Weight. 

Grains. 

Grains. 

Tem. 

Sp.  Gr. 

IX-in. 

1910 

H.I. 

64“ 

Bal.  of  liyd 

Bal.  with  Spec, 
in  air 

Spec,  in  water. . 

Water  displaced. 

12784.2 

2938.5 

9845.7 

1342.8 

64° 

r.9998660 

3.9932463 

7.330 

4281.3 

3.9931126 

3.1280113 

.8651013 

IX-in. 

1910. 

H.2. 

G4° 

Water  displaced. 

12784.2 

2996.7 

4329.6 

9787.5 

i332!o 

64° 

1.9998660 

3.9906718 

3.9905378 

3.1247976 

.8657402 

7.341 

Section  II. — Mechanical  Tests. 

396.  THE  TESTIHG-HACHIHE  affords  the  means  of 
ascertaining  those  properties  of  metals  on  which  the  endurance 
of  guns  is  believed  mainly  to  depend. 

As  yet,  however,  no  standard  of  properties  has  been  deter- 
mined, nor  is  it  believed  to  be  practicable  to  fix  such  standard 
except  by  connecting  the  mechanical  tests  of  a metal  with  the 
endurance  under  the  powder-proof  of  the  <>:uns  made  from  it. 

397.  The  Rodman  Testexg-machine. — This  instrument  is 
used  to  determine  the  capacity  of  any  metal  to  resist  a tensile, 
transverse,  torsional,  or  crushing  force.  It  is  also  used  to  ob- 
tain the  indenting-force,  and  an  internal  force  can  be  applied 
for  bursting  hollow  cylinders, 

398.  Bowee  Exerted. — By  a combination  of  levers  and 
cog-wheels  the  action  of  the  power  employed  is  greatly  aug- 
mented and  transmitted  to  the  specimen  under  trial. 


CAST  GUXS. 


133 


The  machine  consists  essentially  of  a system  of  three  levers, 
AC,  A'C'  and  A"C".  (Fig.  59.) 

The  position  of  the  fulcrum  in  each  of  these  cases  is  denoted 
by  F,  F'  and  F''  respectively.  The  power  is  applied  at  P,  and 
the  position  of  the  weight  is  denoted  by  W.  The  levers  are 
connected  by  rigid  rods. 


> 

A 

a F 

c 

Fro.  59. 


The  mechanical  advantage  of  the  lever  AC  is  10  to  1 ; that 
of  A'C'  is  20  to  1,  and  that  of  A"C"  is  10  to  1. 

AYe  have,  therefore,  ])y  the  formula  for  compound  levers  : 

5 = ^ + 1 + 15  = 2000. 

399.  EXPLANATION  OF  THE  HODMAN  MA- 
CHINE.— The  MroDLE  Levee,  so  called  because  it  is  inter- 
mediate between  the  other  two,  is  the  upper  lever,  A'F'  (Fig. 
CO).  All  its  bearing  knife-edge  pivots  are  in  the  same  hor- 
izontal plane.  Its  fulcrum,  F',  is  supported  by  an  interior  frame 
which  is  attached  to  the  screw,  D,  above  it.  The  knife-edge 
A'  connecting  by  means  of  a long  vertical  rod,  A'C,  with  the 
small  lever  ^ AF,  is  ninety -seven  inches  from  the  fulcrum,  F',  and 
the  knife-edge  C'  connecting  by  means  of  a strap,  A'H',  with 
the  main  lever,  A"F'',  is  four  inches  and  eighty-hve  hundredths 
from  the  fulcrum  F',  making  a proportion  between  the  two 
arms  of  the  lever  as  20  to  1. 

400.  The  Maest  Lever,  A'^F'',  is  the  one  which  acts  directly 
upon  the  specimen  under  trial,  and  is  acted  upon  by  the  middle 
lever  through  a long  iron  strap,  A"C',  wEich  connects  them. 
All'its  knife-edges  are  in  the  same  plane. 

Its  fulcrum,  F^',  is  supported  by  a pair  of  heavy  iron  stan- 
chions, BP,  fitted  to  the  bed-piece,  EE.  The  knife-edge  K" 
which  is  liidved  with  the  middle  lever  is  ninety  inches  from  the 
fulcrum,  F",  and  the  knife-edge  C^,  w'hich  acts  upon  the  speci- 


I 


134  NAVAL  OKDNANCE  AND  GUNNEET. 

men  under  trial  is  nine  inches  from  the  fulcrum,  F",  making  the 
power  of  this  lever  as  10  to  1. 

401.  The  Small  Levee,  AF,  is  the  one  to  which  the 
weights  are  attached. 

All  its  bearing  knife-edge  pivots  are  in  the  same  plane.  Its 
fulcrum,  F,  is  supported  by  the  lower  end  of  the  guide,  G.G', 
attached  to  the  main  lever  stanchions.  The  knife-edge  C,  con- 
necting with  the  middlelever,  is  turn  and  twenty-five  hundredths 
inches  from  the  fulcrum,  F,  and  the  knife-edge  A,  to  which  the 
weights  are  attached,  is  twenty-two  and  five-tenths  inches  from 
the  fulcrum,  F,  making  the  power  of  this  lever  as  10  to  1. 

402.  Tue  Combikatiox  of  Levees. — A combination  of  the 
small  lever  with  the  middle  lever  gives  a proportion  of  two 
hundred  to  one ; and  a combination  of  all  three  of  the  levers 
gives  a proportion  of  two  tjiousand  to  one.  A weight  of  one 
pound,  therefore,  applied  to  the  platforms  of  the  suspending 
rod,  T,  on  the  small  lever  exerts  a force  of  two  hundred  pounds 
on  the  strap,  A'^C',  connecting  with  the  main  lever,  and  of  two 
thousand  pounds  at  C",  where  the  strain  acts  upon  the  sample. 

403.  Capacity  of  tue  Maciilxe. — The  weights  used  are  of 
two  denominations,  viz.,  half  pounds  and  five  pounds,  repre- 
senting respectively  one  thousand  and  ten  thousand  pounds. 
Smaller  increments  of  strain  than  one  thousand  pounds  are 
noted  on  the  small  lever,  Avhich  is  provided  with  a sliding 
weight  and  graduated  from  zero  to  ten ; each  number  repre- 
senting an  additional  hundred  pounds. 

Of  the  first  denomination,  tliere  are  ten  weights,  represent- 
ing a strain  of  ten  thousand  pounds,  and  of  the  second,  there 
are  nine  weights,  representing  a strain  of  ninety  thousand 
pounds. 

The  aggregate  strains  of  all  the  weights  or  the  capacity  of 
the  machine  being  one  Inmdj'ed  thousand  jiounds. 

404.  The  Cog-wuieel  Geaeixg. — The  lai-ge  vertical  frame, 
EH,  at  one  end  of  the  machine  (Fig.  00),  supports  the  cog-wheel 
gearing  wdiich  is  set  in  motion  by  a craidv. 

To  the  heavy  main  lever  stanchions,  BB,  a guide,  G.G.,  is 
attached  ; through  the  u]>per  end  of  which  the  small  end,  G',  of 
the  middle  lever  passes.  This  guide  ascends  and  descends 
evenly  with  the  screw,  D,  and  tlie  fulcrum,  F',  of  the  lever,  by 
means  of  a rack  and  pinion,  U'L",  at  each  end  of  the  revolving- 
rod,  L.  A mortise  through  the  guide  receives  the  lever  and 
allows  it  a free  motion  to  a limited  extent.  The  lever  is  thus 
maintained  in  a position  always  nearly  horizontal,  while  it  re- 
mains free  to  oscillate  on  its  fulcrum  in  either  direction,  as  the 
strain  or  the  weights  may  preponderate.  The  supports  of  the 


CAST  GUA"S. 


135 


small  lever  are  attached  to  the  guide,  G.G',  so  that  it  ascends  or 
descends  with  the  middle  lever. 


O 


405.  lIuLTiPLicATioisr  OF  Power. — Fifty  timns  of  the  hand- 
crank,  I,  gives  one  turn  to  the  horizontal  wheel,  M,  at  the  top 
of  the  frame,  E. 

A screw  nut  is  cut  in  the  axis  of  this  wheel,  through  which 
the  vertical  screw,  D,  passes.  This  wheel,  when  turned,  ele- 
vates or  depresses  the  screw,  and  sets  in  motion  all  the  mov- 
able parts  of  the  machine. 

Two  turns  of  this  horizontal  wheel  move  the  vertical  screw 
one  inch,  and  this  requires  one  hundred  turns  of  the  hand- 
crank,  and  gives  one-tenth  of  an  inch  of  motion  to  the  knife 
edge  of  the  main  lever,  where  the  strain  on  the  samole  is  ex- 
erted. 


136 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  cranh  to  which  the  power  is  first  communicated  moves 


distance  of  seve.ity-two 


seventy- 
each 


inches  at  each  turn,  and 
two  hundred  inches  for 
tenth  of  an  inch  of  motion  at 
the  straining-point  of  the  ma- 
chine. Such  a great  power  is 
needed  only  when  heavy  strains 
are  exerted. 

Wlien  heojinniuo:  a strain,  or 
Avhen  loweringdown  the  levers, 
the  small  pinion,  o,  on  the 
crank  shaft  is  thrown  ont  of 
gear,  by  lifting  the  latch,  X, 
and  shifting  the  shaft ; tlius 
bringing  into  action  the  large 
pinion,  R,  which  change  of 
gearing  gives  a velocity  nine 
times  as  great  to  all  the  mov- 
able parts  of  the  machine,  but 
the  force  exerted  whl  be  only 
one-ninth  as  great  as  before. 

4-06.  The  Torsion  Lever, 
L',  works  between  two  heavy 
pillow-blocks,  B',  fitted  on  the 
bed-frame,  E,  and  within  these 
pillow-blocks  the  journals  of 
the  torsion-lever  revolve.  Its 
axle  has  a cylindrical  aperture 
concentric  with  its  axis.  This 
lever  is  set  in  motion  by  a 
chain,  S,  whicli  connects  di- 
rectly with  the  middle  lever 
through  the  strap,  S. 

407.  Pedestals  for  Trans- 
verse Strains.— Two  hollow 
movable  pedestals,  TT,  are  at- 
tached to  the  bed-frame,  E, 
fitted  with  steel  knife-edges, 
which  serve  as  points  of  sup- 
port for  the  test-bars. 
Horizontal  braces  secure  the  stability  of  the  frame-work  of 
tll6 

408.  W(3rKIHG  the  MACHIXE.— Adjustments.— All 
the  working  knife-edges,  and  the  seats  on  which  they  hear,  are 
made  of  hardened  cast-steel ; the  other  principal  parts  of  cast-iron. 


Fig. 


01. — Testing--macMne. 
Eleyation. ) 


(End 


CAST  GUNS. 


137 


Before  beginning  a test,  it  is  necessary  to  see  that  all  the 
knife-edges  are  properly  adjnstecl,  and  that 'the  vertical  screw 
through  the  horizontal  wheel  on  the  top  of  the  machine  is  run 
down  its  full  length,  to  obtain  all  its  scope. 

To  adjust  the  equilibrium,  there  is  a small  horizontal  rod, 
B',  with  a weight  working  upon  it,  which  is  attached  to  the 
upper  end  of  the  slide,  G.Gr',  supporting  the  small  lever. 

Before  the  specimen  is  secured  in  its  place,  the  machine 
must  be  accurately  balanced  by  moving  the  weight,  W',  of  the 
adjusting-rod  either  in  or  out,  as  it  may  require.  The  final 
and  accurate  adjustment  is  made  with  the  small  brass  weight, 
W",  attached  to  the  end  of  the  small  level’. 

409.  The  Sample  Holdees  in  all  forms  of  strain,  excepting 
that  of  torsion,  are  attached  at  one  end  to  a stirrup,  C'',  on  the 
main  lever,  and  at  the  other  to  the  bed-frame.  "To  apply  the 
strain  to  the  specimen,  the  hand-crank,  I,  is  turned  with  regu- 
larity in  the  direction  which  raises  the  screw,  and  sets  in  motion 
all  the  movable  parts  of  the  instrument. 

The  slide  on  the  small  lever,  S",  is  moved  gradually,  just 
keeping  its  equipoise ; as  the  strain  is  increased,  weights  are 
supplied  at  P,  in  such  manner  as  will  keep  the  lever  erenly 
balanced,  so  that  the  force  applied  at  the  instant  of  breaking 
may  be  accurately  determined  by  counting  the  weights  then  on 
the  platforms.  • 

410.  Texsile  Steaix. — After  the  density  of  a specimen  has 
been  ascertained,  and  before  it  is  inserted  in  the  holders,  its 
smallest  diameter  is  accurately  measured  and  recorded.  This  is 
done  by  sliding-calipers,  an  instrument  provided  with  a Yenier, 
which  measures  hundredths  of  an  inch,  and  thousandths  of  an 
inch  may  be  readily  determined  by  a practiced  eye. 

The  specimen  is  now  fitted  between  the  holders  used  for 
the  purpose;  one  of  which  is  attached  to  the  shackle  hung  on 
the  stirrup  of  the  main  lever ; the  screw,  U,  connecting  with 
the  bed-frame,  is  then  run  up  by  the  handles,  II',  underneath, 

. until  the  specimen  can  be  caught  between  the  holders  that  fit 
on  its  upper  end. 

After  the  sample  is  secured  between  the  holders,  the  screw 
is  run  down  until  a sufficient  strain  is  obtained,  to  keej)  them 
in  place.  Then  proceed  with  the  test. 

The  breaking-weight  is  divided  by  the  area  of  the  smallest 
diameter  of  the  specimen,  and  the -quotient  gives  the  tenacity, 
or  the  strength  per  square-inch. 

That  is,  let  a represent  the  breaking  weight,  & the  area,  and 
X the  tenacity  per  square-inch. 

5 ; 1 sq.  in.  ~ a x. 


I 


138 


NAVAL  ORDNANCE  AND  GUNNERY. 


Examples. 


Sample  No.  4.  H.  Logs. 

Brealdng-weiglit,  50500 4.7032914 

Diameter,  1.25  in.;  area  (^r^),  1.22719  in.  .0.0889099 

Tenacity  per  sq.  in.,  41151  lbs 4.6143815 

411.  The  following  table  contains  the  area  and  the  log- 
arithms for  aU  the  variations  of  diameter  likely  to  occur  in 
tensile  samples : 


Diam. 

Area. 

Logs. 

Diam. 

Area. 

Logs. 

Diam. 

Area. 

Logs. 

1.190 

1.11220 

.0461839' 

1.204 

1.13853 

.0563429 

1.297 

1.32120 

.1209093 

1.191 

1.11407 

.0469135 

1.205 

1.14042 

.0570639 

1.298 

1.32324 

.1210393 

1.192 

1.11594 

.0476425 

1.206 

1.14231 

.0577845 

1.299 

1.32528 

.1223083 

1.193 

1.11782 

.0433707 

1.207 

1.14421 

.0585045 

1.300 

1.32732 

.1229707 

1.194 

1 11909 

.04909851 

1.208 

1.14610 

.0592237 

1.301 

1.32937 

.1230446 

1.195‘  1.12157 

.0493257 

1.209 

1.14800 

.0599425 

1.302 

1.33141 

.1243120 

1.196 

1.12345 

.0505523 

1.210 

1.14990 

.06060071 

1 303 

1.33346 

.1249788 

1.197 

1.12533 

.0512783 

1.290 

1.30698 

.11626931 

1.304 

1.33550 

.1256451 

1.198 

1.12721 

.0520035 

1.291 

1.30901 

.1169423 

1.305 

1.33755 

.1263109 

1.199 

1.12909 

.0527283 

1.292 

1.31104 

.1176148 

1.303 

1.33960 

.1269763 

1.20» 

1.1S097 

.0534523 

1.293 

1.31307 

.1182868 

1.307 

1.34165 

.1276411 

1.201 

1.13280 

.0541759 

1.294 

1.31510 

.1189583 

1.308 

1.34370 

.1283033 

1.202 

1.1347.5 

.0548989 

1.295 

1.31713 

.1196293 

1.309 

1.34570 

.1289091 

1.203:  1.13664 

1 

.0556211 

1'296 

1.31617 

.1202998 

1.310 

1.34782 

.1296325 

412.  Transvekse  Strain. — For  determining  the  transverse 
strength  of  metals,  a specimen-bar  is  taken  two  or  three  feet 
long,  and  about  two  inches  square.  It  is  prepared  for  the  test 
with  a slight  dressing  with  the  hie  or  grind-stone,  on  one  of  its 
faces  near  each  end,  in  order  that  the  bar  may  bear  more  evenly 
against  the  supports  when  under  the  strain.  The  middle  of  the 
bar — the'  part  where  the  fracture  occurs — is  dressed  in  like 
manner  on  each  of  its  four  faces,  in  order  that  its  breadth  and 
depth  in  this  part  may  be  accurately  measured. 

413.  To  Place  tue  Bar. — Run  the  screw,  U,  down  nearly 
level  with  the  bed-frame,  out  of  the  way ; slide  the  pedestals  to 
the  proper  distance  on  either  side,  to  accommodate  the  length 
of  the  specunen.  Suspend  the  long  link,  S (Fig.  62),  from  the 
same  shackle  used  in  the  tensile-strain,  and  pass  the  bar  through 
the  pedestals  and  the  long  link,  so  that  it  rests  in  the  middle  of 
its  length  on  the  knife-edge  in  the  bottom  of  the  link.  The 
latter  is  then  drawn  upward  until  the  ends  of  the  bar  bear 


CAST  GUXS. 


139 


firmly  against  the  knife-edge  supports  in  the  pedestals,  which 
must  be  at  equal  distances  from  the  link. 

411.  The  Deflection. — The  breaking-force  is  applied  on 
the  under  side  of  the  bar,  in  the  middle,  and  forces  it  upwards 
against  the  supports  at  the  ends. 

The  deflection  is  measured  by  inserting  a graduated,  tapered 
metallic  scale  between  the  upper  surface  of  the  bed-frame  and 
the  under  side  of  the  bar-holder,  directly  beneath  the  forcing- 
line of  the  latter,  against  the  centre  of  the  bar.  The  space 
enlarges  as  the  bar  bends,  and  the  graduated  wedge  measures 
minutely  the  deflection  of  the  bar  at  any  stage  of  its  progress. 

A record  is  kept  of  the  deflection’’’'  and  which  shows 

the  quantity  of  deflection  and  permanent  set  under  a given 
pressure,  which  is  designed  to  lie  near  to,  but  somewhat  less 
than,  the  minimum  breaking-weight.  Also  of  the  “ last  deflec- 
tion,” which  gives  the  amount  of  deflection  under  the  pressure 
of  the  breaking-weight.  i 

415.  The  q/"  represents  the  weight  in  pounds 

required  to  break  a bar  one  inch  square,  rigidly  supported  at 
one  end ; the  weight  being  ai^plied  at  a distance  of  one  inch 
from  the  point  of  support.  For  square  bars  it  is  determined 
by  the  formula — 

=:  S,  the  unit  of  strength. 

46  a* 

I = the  length  between  the  supports. 

TF  = the  breaking-weight. 

0 = the  breadth  of  the  bar. 

d — the  depth  of  the  bar. 

The  breadth  and  depth  are  accurately  measured  near  the 
fracture ; and,  as  the  dimensions  are  irregular,  it  is  proper  to 
measure  in  three  places  for  each ; one  measure  to  be  taken  in 
the  middle  of  the  bar,  and  the  other  two  near  the  corners. 
The  mean  of  the  three  measures  to  be  taken  as  the  true  dimen- 
sion. If  the  bar  is  defective,  the  results  cannot,  of  course,  be 


relied  on. 

Example. 

Proof  Ear  No.  4S4.  Logs. 

6 =:  1.969  (mean  of  three  measurements) 0.2942457 

d =:  1.9683  (mean  of  3)  log.  0.2940913  X 2 = . . 0.5881826 


— 0.8824283 

i Z X TF=  2^0  X 13900  = 69500  4.8419848 


Transverse  strength  = S = 9111  lbs 3.9595565 

O 


140 


NAVAL  ORDNANCE  AND  GUNNERY. 


416.  Torsional  Strain. — For  determining  the  torsional 
strain,  or  the  weight  required  to  break  hj  twisting,  a specimen- 
bar  is  used,  wliich  is  long  enough  to  project  hejmnd  the  jour- 
nals of  the  torsion-lever,  and  receive  the  indices,  <3',  whicli  are 
attached  to  its  ends,  a.  The  parts  against  which  the  holding- 
keys,  k',  are  pressed  are  made  square.  All  the  other  parts  are 
round. 

The  part  between  the  keys  is  dressed  to  a true  cylinder, 
the  length  of  which  should  not  be  less  than  three  diameters. 

This  length  is  necessary  to  allow'  a full  development  of  the 
fracture  to  occur  within  the  dressed  part  of  the  specimen. 
The  distance  between  the  keys  is  nineteen  inches. 

417. . To  Place  the  Specimen. — The  bar  passes  through  the 
axle  of  the  torsion-lever. 

One  end  is  held  tirmly  to  the  pillow-block  of  the  bed-frame, 
and  the  other  to  the  journal  of  the  torsion-lever,  L',  by  means 
of  keys,  Kb  The  axis  of  the  bar  is  made  to  coincide  with  the 
axis  of  the  torsion-lever,  by  passing  its  ends  through  concentric 
rings,  r,  inserted  in  recesses  provided  for  the  pui-pose,  before 
the  keys  are  fixed  in  their  places.  Indices,  are  attached  to 
the  projecting  ends  of  the  bar  and  adjusted  to  the  zero  of  the 
are  beneath,  before  the  strain  is  commenced. 

The  diameter  of  the  specimen  is  carefully  measured  before 
it  is  secured  in  the  journal.  Bring  the  keys  up  on  the  bottom, 
until  the  bar  rests  firmly  upon  them,  then  key  up  from  the  top 
to  keep  it  firmly  in  its  place.  Connect  the  chain  on  the  tor- 
sion-lever to  the  strap  communicating  with  the  middle  lever, 
and  proceed  with  the  test. 

IVhen  a bar  is  in  the  machine  for  torsion,  the  lever.  Lb  is 
placed  at  its  lowest  point,  but  sometimes  the  screw,  D,  ascends 
to  its  highest  limit  before  the  bar  breaks.  AVhen  this  happens 
the  lever  is  propped  up,  the  chain  is  detached  and  shortened  by 
removing  its  upper  link  ; then,  on  its  being  again  attached, 
the  work  is  resumed  and  the  strain  extended  until  the  bar 
breaks. 

418.  liecovcling  the  Strain. — In  torsional  strains  the  main 
lever  of  the  testiug-machine  is  inoperative.  The  recorded 
breaking-weight  then  is  only  two  hundred  times  greater  than 
the  actual  weights  on  the  platforms,  which  is  equal  to  one-tenth 
of  the  usual  reading  in  other  tests.  But  as  the  torsion-lever  is 
thirty  inches  long  from  its  axis  to  the  point  where  the  centre 
of  the  chain  acts  upon  it,  the  weight  as  above  ascertained  is 
multiplied  by  thirty,  and  the  product  represents  the  strain  ex- 
erted at  a point  one  inch  from  the  axis  of  the  strained  bar. 
In  practice  it  is  found  more  convenient  to  read  off  the  weights 


CAST  GUNS. 


141 


for  torsion  in  the  same  manner  as  in  other  tests,  and  to  multiply 
that  reading  by  three. 

419.  The  Deflection. — Although  one  end  of  the  bar  is  firml  y 
fixed,  it  will  yield  a little  by  its  compression  on  the  heys,  and 


Fig.  G2. — Stirrap  for  Holding  Indenting  Apparatus. 

therefore  its  angular  deflection  is  determined  by  the  diffenmce 
between  the  reading  on  the  arcs. 

The  deflection  of  the  bar  is  noted  at  each  addition  of  a cer- 


142 


NAVAL  OEDNANCE  AND  GUNNERY. 


tain  numbez'  of  pounds  of  pressure ; and  at  eaeli  addition  of, 
say,  five  hundred  or  a thousand  pounds,  the  bar  is  released 
from  strain  and  the  permanent  set  ascertained.  The  greatest 
anffle  of  deflection  and  the  breaking-weight  are  also  recorded. 

The  torsional  strength  is 

Q tor 

in  which 

w = breaking-weight, 

T — radius  of  torsion-lever, 
d — diameter  of  specimens. 

420.  Crushtno-fokce. — The  samples  submitted  to  the  test 
of  compression  are  small  cylinders,  the  lengths  of  which  are 
generally  two  and  a half  times  their  diameters.  Bars  of 
greater  length  than  these  diameters  are  liable  to  bend  under 
the  pressure  before  the  fi’acture  occurs ; and  if  the  length  be 
less  than  two  diameters,  the  fracture  in  its  regular  form  may 
not  be  fully  developed,  and  a portion  of  the  sample  may  be 
pulverized  or  reduced  to  small  grains.  The  ends  of  each  sam- 
ple are  made  perfectly  parallel  and  pei’pendicular  to  the  axis, 
so  that  all  parts  of  the  sample  will  be  equally  pressed. 

421.  Placing  the  Specimen. — Fig.  62  shows  the  form  of 
the  stirrup  used  in  holding  the  instruments  for  crushing.^  burst- 
ing, and  indenting  samples  when  the  straining  force  is  applied. 
/S'  is  a stirrup  attached  at  its  upper  end  to  the  straining-stirrup, 
C" , on  the  main  lever ; and  P is  attached  to  the  bed-frame  by 
means  of  the  screw  U. 

y is  a block  of  kon  upon  which  the  sample  may  rest. 

The  samples  or  the  instruments  for  holding  them  are 
inserted  in  the  space,  T. 

422.  llecording  the  Compression. — The  dimensions  of  the 
sample  are  carefully  measured  before  placing  it.  The  depres- 
sion or  permanent  set  at  every  five  thousand  pounds,  for 
instance,  are  then  carefully  noted.  The  breaking-weight  is 
recorded  as  well  as  the  angle  of  fracture  of  the  specimen. 

The  strength  per  square  inch  AviU  be 

g _ weight 
area 

423.  Indenting-force. — The  comparative  softness  or  hard- 
ness of  metals  is  determined  by  the  bulk  of  the  cavities  or  in- 
dentations made  by  equal  pressure;  the  softness  being  as  the 
bulk  directly,  and  the  hardness  as  the  bulk  in\’ersely. 

424.  Indenting-tool. — Of  the  different  forms  of  cavity 


CAST  Ginsrs. 


143 


made  by  indenting-tools,  that  of  the  pyramid  is  preferred, 
because  of  its  simplicity  and  the  ease  with  which  its  volume 
may  be  computed. 

The  instrument  used  for  making  indentations  is  represented 
by  Fig.  63. 


Fi^.  G3. 


The  indenting  part  of  the  tool  is  in  the  form  of  a pyramid, 
having  a rhombus  for  its  base,  the  diagonals  of  Avhich  are 
respectively  one  inch  and  two-tenths  of  an  inch  ; the  height  of 
tlie  pyramid  one-tenth  of  an  inch. 

In  late  experiments  the  form  of  the  pyramid  has  been 
changed  and  improved  somewhat,  by  causing  it  to  make  a 
longer  line,  and  mark  minute  diiferences  more  accurately. 

425.  Standard  of  Comparison. — The  volume  of  an  indenta- 
tion made  with  this  tool  is  taken  as  the  measure  of  the  work 
required  to  produce  it,  and  is  inversely  proportional  to  the 
hardness  of  the  specimen,  that  is  (denoting  by  II  the  hai’dness 
of  any  specimen). 

n=\ (I.) 

V 

I denoting  any  convenient  constant,  and  r the  volume  of 
the  indentation  corresponding  to  II. 

It  has  been  found  by  experiment  that  a pressure  of  10,000 
pounds  on  the  base  of  the  pyramid,  makes  an  indentation,  in 


144 


NAVAL  ORDNANCE  AND  GUNNERY. 


the  softest  metals  used  in  guns,  about  nine-tenths  of  an  inch 
long. 

The  maxiimim  indentation,  one  inch  in  length,  of  the  in- 
strument is  therefore  assumed  as  the  unit  of  hardness ; there- 
fore, denoting  by  V the  volume  corresponding  to  an  indenta- 
tion one  inch  in  length,  we  obtain  from  equation  (1), 

^ = ^or 
and  in  general, 


or,  putting  I = the  number  of  tenths  of  an  inch  in  the  length 
of  any  given  indentation, 

V 1000 
v~  r ’ 

since  pyramids  are  to  each  other  as  the  cubes  of  any  similar  di- 
mensions. 

A pressure  of  less  than  10,000  will  probably  be  found  better 
suited  to  the  purpose,  with  the  improved*tools.  Abetter  stand- 
ard of  comparison  may  be  found  in  some  metal  of  uniform 
density  and  hardness,  easily  obtainable  in  all  places. 

The  silver  coin  of  the  country  best  fullils  these  conditions. 
The  volume  of  the  cavity  made  in  this,  by  the  adopted  unit  of 
pressure,  may  be  assumed  as  the  unit  of  hardness;  and  this 
divided  by  the  volume  of  the  cavity  in  any  sample  tested,  will 
denote  the  hardness  of  that  sample  as  compared  with  that  of 
silver  coin.* 

426.  Ekeoes  of  the  Eodman  Machixe. — The  errors  inci- 
dental to  the  use  of  this  machine  are  due  to  three  causes : 

1st.  AVeight  of  its  different  movable  parts. 

2d.  Motion  of  the  centres  of  gravity  of  the  levers  towards  or 
from  their  fulcrnms. 

3d.  Friction. 

The  First  cause  of  error  is  avoided  in  practice  by  means  of 
the  adjusting-weights,  already  described. 

The  system  is  brought  into  perfect  equilibrium,  so  that 
any  increase  of  AV  will  be  balanced  by  a proportionate  increase 
of  P. 

The  Second  cause  of  error  is  comparatively  unimpoi-tant, 


Rodman. 


CAST  GUA^S. 


145 


because  the  levers  AC  and  A'C',  are  so  adjusted  as  never  to 
make  a large  angle  with  a horizoTital  line  passing  through  the 
fulcrum,  and  in  the  case  of  the  lever  A"C^',  which  makes  a 
lai’ger  angle,  the  shape  is  such  as  to  bring  the  centre  of  gravity 
very  near  the  centre  of  motion. 

Let  D denote  the  distance  through  which  the  centre  of 
gravity  moves. 

a denote  the  distance  of  the  centre  of  gravity  from 
the  centre  of  motion. 

L denote  the  angle  described  by  the  lever  during  the 
breaking  of  a specimen. 

In  general  the  levers  are  so  adjusted  that  the  line  connect- 
ing the  centres  of  gravity  and  of  motion  is  horizontal  when  the 
movement  of  the  lever  is  half  completed. 

. ■ . D = a versine  ^ L. 

It  is  evident  that  one  or  both  of  these  factors  is  very  small 
in  each  case. 

The  Third  cause  of  error  is  made  as  small  as  possible  by  the 
use  of  knife-edges  and  steel  plates,  and  is  practically  inconsid- 
erable. 

The  determination  of  the  absolute  breaking  and  other 
strains  involve  the  elimination  of  errors  due  to  friction,  etc., 
but  for  obtaining  the  comparative  strength  of  specimens,  the 
machine  is  all  that  can  be  desired. 

427.  MoDiFicATioisrs  of  the  Machine. — This  machine  is 
arranged  for  shoi't  tensile  specimens  only,  and  as  the  power  is 
at  present  applied,  admits  of  only  a very  slight  stretch,  which 
is  unsuifed  to  the  breaking  of  specimens  giving  elongations  of 
several  inches. 

A change  has  therefore  been  tried  in  the  lower  fastening  of 
the  specimen,  by  which  the  power  was  applied  at  that  point,, 
through  a screw  and  cogwheels,  and  tins  arrangement  was 
foimd  to  answer  the  pmgiose  in  the  most  satisfactory  manner.* 

Another  change  was  made  in  order  to  get  a continuous  in- 
crease in  the  weight  upon  the  scale-beam,  instead  of  adding 
one  weight  at  a time  as  is  generally  done.  This  was  accom- 
plished by  using  a chain  for  a weight,  which,  being  wound  upon 
a reel,  was  reaclily  reeled  into  the  scale  as  fast  as  required  to 
balance  the  strain  upon  the  specimen.  The  principal  advan- 
tage of  this  method  is  in  working  the  indicator. 

428.  The  Indicator. — In  connection  with  the  testing- 
machine  it  has  been  found  desirable  to  have  an  instrument 
which  would  give  a continuous  curve  representing  the  elonga- 


10 


* King. 


14G 


NAVAL  ORDNANCE  AND  GUNNERY. 


tions  and  corresponding  tensile-strains  for  specimens  of  various 
kinds,  in  order  to  arrive  at  the  exact  dynamical  value  of  the 
metal. 

429.  A.n  instrument  has  been  devised  for  this  purpose  (Fig. 
64).  It  consists  of  a brass  frame,  AB,  supporting  a vertical  cy- 
linder, C,  revolved  by  the  endless  screw,  S.  This  screw  being 
turned  by  the  tape,  T,  which  draws  around  the  pulley,  P,  as  the 

weight,  AY,  is 
iNDic.VTOE  wound  along  the 

(for  tensUe  strains  and  elongation.)  SCale-beUm 

AYhen  the  chain 
was  used  as  a 
weight,  the  cy- 
linder revolved 
as  the  chain  was 
paid  into  the 
scale. 

This  arrange- 
ment causes  the 
cylinder  to  re- 
volve as  the 
weight  or  strain 
upon  the  speci- 
men increases 
or  diminishes, 
and  if  the  mark- 
er, M,  remains 
stationary,  it 
will  describe  a 
horizontal  circle 

upon  the  paper  with  which  the  cylinder  is  covered.  Starting 
from  the  zero-point  of  the  scale,  the  length  of  any  arc  of  the 
circle  will  represent  the  strain  upon  the  specimen  at  the  instant 
the  marker  has  arrived  at  the  end  of  the  arc. 

430.  If  now  the  elongation  of  a given  portion  of  the  speci- 
men carries  the  marker  in  a direction  parallel  to  the  axis  of 
the  cylinder,  it  is  clear  that  the  curve,  NO,  described  upon  the 
paper,  will  accurately  and  continuously  represent  the  relation 
between  the  elongation  of  the  specimen  and  the  corresponding 
strain  upon  it.  In  order  to  move  the  marker  in  this  manner, 
it  is  connected  with  one  end  of  the  specimen  by  the  clamp,  Q', 
which  tits  into  a centre-punch-mark  on  the  specimen,  while  the 
frame  and  cylinder  are  attached  to  the  other  end,  Q,  of  the 
specimen  in  a similar  manner. 

431.  The  portion  of  the  specimen  between  the  two  centre- 


CAST  GIIN'S. 


147 


puncla-marks  is  evidently  the  only  portion  wliose  elongation 
will  move  the  marker  along  the  paper,  and  the  space  passed 
over  by  the  marker  divided  by  the  original  length  of  this  por- 
tion, will  give  the  elongation  per  unit  of  length  of  the  speci- 
men, or  the  per  cent,  of  elongation ; and  the  area  hounded  by 
the  curve,  NO,  and  the  co-ordinates,  NR  and  RO,  measures 
the  worli,  of  breaking  the  specimen. 

432.  Fig.  G5  shows  examples  of  the  record  made  by  the 
Indicator.  It  will  be  seen  that  in  the  specimens  indicated,  the 


first  part  of  the  elongation  gives  a very  slight  curve,  which 
shows  that  the  elongation  increases  rather  more  rapidly  than 
the  strain  upon  the  specimen. 

This  part  of  the  curve  extends  from  the  origin  to  the  point 
a.  When  the  specimen  begins  to  elongate  freely,  and  there  is 
a well-defined  change  in  the  rate  of  increase,  the  point  a proba- 
bly coincides  with  the  elastic  limit. 

The  strain  increases  as  the  elongation  continues  almost  up 


148 


NAVAL  ORDNANCE  AND  GIINNEET. 


to  tlie  breaking-point,  h.  Tliis  shows  that  the  tenacity  of  metai, 
which  has  been  stretched  beyond  the  elastic  limit,  is  not  en- 
tirely destroyed,  as  is  commonly  believed,  bnt  the  work  of  the 
rupture  has  ljut  just  commenced. 

433.  Just  before  rupture  takes  place,  in  case  of  good 
wrought-iron,  the  specimen  is  observed  to  suddenly  contract  at 
some  point,  sometimes  at  two,  and  very  rarely  at  a greater 
number;  strain  slightly  diminishing  at  the  instant,  and  the 
specimen  breaks  generally  with  a sudden  snap,  though  very 
soft  iron  sometimes  breaks  so  cpiietly  as  not  to  be  heard  at  all. 

434.  The  effect  of  the  elongation  of  specimens  in  this  man- 
ner is  to  change  the  smooth  surface  of  the  specimen  to  a I'ough 
and  scaly  appearance,  and  in  case  of  bronze  the  specimen  be- 
comes so  irregular  as  to  resemble  a roll  of  putty  flattened  in 
various  directions  between  the  Angers.  The  elon2:ation  of  steel 
develops  innumerable  fine  cracks  nearly  perpendicular  to  the 
surface. 

435.  In  breaking  a specimen  a second  or  third  time,  it 
would  seem  that  the  metal  must  get  weaker,  especially  since 
the  sudden  breaking  produces  a violent  shock  ; but  on  the  con- 
trary, the  specimen  evidently  breaks  at  the  weakest  point,  and 
the  shock  and  previous  stretching  have  not  been  sutiicient  to 
reduce  the  strength  of  the  next  weakest  part  of  the  specimen 
below  that  of  the  first  one.  It  is  sometimes  found  that  even 
the  third  breaking  requires  a greater  strain  than  the  second. 

436.  Much  labor  in  turning  out  specimens  may  be  saved  by 
the  use  of  sockets  with  conical  wedges  (Fig.  GG),  which  have 
been  devised  for  the  purpose  of  taking  hold  of  the  middle  por- 
tion of  broken  specimens,  and  breaking  them  a second  time. 
It  will  be  seen  that  by  cutting  out  the  specimen  barely  large 
enough  to  turn  up  to  the  required  diameter,  a great  saving  may 
be  effected  over  the  usual  method  which  requires  the  ends  of 
the  specimen  to  be  quite  large,  while  the  middle  portion,  for 
nearly  the  whole  length,  has  to  be  turned  do^m  to  a much 
smaller  diameter. 

Quite  a number  of  specimen  of  each  kind  should,  if  possi- 
ble, be  tested  under  as  nearly  identical  circumstances  as  practi- 
cable, in  order  to  get  reliable  mean  results. 

437.  The  usual  form  of  specimens  for  tensile  strain  is  such, 
that  unless  the  weakest  point  happens  to  occur  at  the  smallest 
section  of  the  specimen,  the  fractured  area  will  be  larger  than 
the  measrired  section.  By  using  longer  cylindical  specimens 
this  source  of  error  will  be  avoided,  in  all  but  exceptional  cases, 
arising  from  flaws  or  other  defects.  Besides,  the  usual  or 
standard  form  of  specimen  admits  of  transverse  strains  due  to 


CAST  GUNS. 


149 


the  iineqiial  bearing  of  the  ends  in  the  sockets  of  the  testing- 
machine.  This  defect  is  greatly  improved 
by  using  longer  specimens. 

438.  The  simple  measure  of  the  strain 
required  to  break  a piece  of  metal,  without 
regard  to  the  elongation  produced  before 
rupture  takes  place,  is  not  a measm*e  of 
what  occurs  in  practice ; for  when  a bar  of  ^ 
iron  is  broken,  a certain  space  is  passed  over 
by  the  breaking-force  in  separating  the 
fibres,  and  as  this  space  bears  no  analogy 
whatever  to  the  tensile  strength  of  the 
metal,  it  must  come  in  as  an  independent 
factor.  For  example,  the  metal  of  cannon 
is  stretched  at  every  discharge ; and  when- 
ever metal  is  subject  to  a variable  strain, 
there  must  be  a corresponding  change  of 
length.  These  elongations  may  be  very 
small  in  amount ; so  small,  in  fact,  as  to  be 
inappreciable  in  ordinary  measurements,  but 
it  is  no  less  certain  that  they  exist. 

439.  EIEIILE’S  TESTIEG-MA- 
CEillsE. — This  is  a good  example  of  a 
horizontal  testing-machine  adapted  to  testing 
rope,  chain,  wire,  bar  or  plate  iron,  etc.  The 
iron  frame,  CC  (Fig.  67),  and  the  timbers 
which  support  the  iron  guides,  SS,  are  all 
firmly  secured  to  a solid  foundation  of  ma- 
sonry. 

440.  The  Levees. — Enclosed  in  the 
frame,  CC,  is  a heavy  intermediate  lever, 

A,  one  fulcrum  of  which  bears  against  a Fig.  G6. 

smooth  steel  surface  composing  a part  of 

the  frame.  - The  lower  fulcmm,  D,  presses  against  the  clevis, 
E,  which  connects  directly  with  the  clamps  holding  one  end  of 
the  test  specimen.  This  lever  is  suspended  at  the  larger  end 
by  clevises,  F,  swinging  from  the  iron  frame,  C,  and  at  the 
smaller  end  by  a link  or  rod  connecting  with  the  differential 
lever,  or  scale-beam,  G. 

441.  Eecoedixg  the  Stkain. — On  this  beam  is  an  ordinary 
weight-dish,  H,  upon  which  standard  weights  are  placed  for 
recording  the  strain  to  which  the  specimen  is  being  subjected. 
A weight  of  one  pound  on  the  weight-dish  indicates  a strain  of 
one  thousand  pounds  on  the  specimen  under  trial. 

442.  Application  of  Powee. — At  the  other  end  of  this 


150  NAVAL  OKDNANCB  AND  GUNNEET. 

machine  is  placed  a hydraulic  pump  and  jack,  I ; the  cross-head, 
L,  carrying  the  clamps  for  one  end  of  Ihe  specimen,  being  at- 
tached to  this  by  the  bolts  MM,  The  whole  arrangement 


Fig  67. — Eiehlc  Testing-macliine. 


travels  along  a railway,  SS,  on  low,  strong  wheels,  and  may  be 
secured  in  any  position,  to  accommodate  the  length  of  the  speci- 
men, by  keys  dropping  into  slots  on  the  railway.  The  power  is 
applied  to  the  jack,  I,  by  the  pump,  J,  while  the  scale-beam  is 
kept  horizontal  by  the  use  of  the  weights ; its  equipoise  being 
indicated  by  a pointer  attached  to  the  centre  fulcrum  of  the 
beam. 


413.  Adjustment. — When  the  specimen  is  in  position,  the 
lever  and  beam  must  be  balanced  by  means  of  the  balance-cup, 
K,  hanging  from  the  extreme  end  of  the  scale-beam.  All  the 
knife-edge  bearings  and  fulcrums  are  made  of  steel,  and  are 


CAST  GUNS. 


151 


very  strong  and  true.  As  each  part  swings  perfectly  free, 
there  is  comparatively  no  friction,  and  the  strain  on  a specimen 
can  he  weighed  to  within  a few  pounds. 

444.  The  Diffekential  Lever. — Fig.  68  represents  the 
differential  lever  and  scale-beam  used  in  tliis  instrument. 

The  link  O is  connected  with  the  intermediate  lever,  A (Fig. 
67).  If  a weiglit  of  one  hundred  pounds  he  suspended  from 
the  link  O,  one  half,  or  fifty  pounds,  will  be  suspended  by  the 
hearing  P,  and  fifty  pounds  by  the  hearing  P'.  These  weights 
being  transmitted  through  links  to  the  hearings  Q and  Q',  P and 
P'  are  equidistant  from  the  bearing  T,  while  Q and  Q'  are  at 
unequal  distances  from  the  centre  bearing  or  fulcrum,  R.  If 
the  distance  Q'  R be  6^  inches,  and  Q R be  inches,  and  the 
weight  at  Q and  Q'  50  pounds,  then  the  moment  on  the  side 
Q will  be  50  X 5|-  =:  275 ; and  the  moment  on  the  side  Q'  will 
be  50  X 6|-  = 325.  The  difference  of  these  moments,  or  325  — 
275  = 50,  will  be  the  unbalanced  moment;  and  if  a weight  of 
5 pounds  be  suspended  on  the  scale-beam  at  a distance  of  10 
inches  from  the  fulcrum,  R,  it  will  counter-balance  the  extra 
moment  on  the  side  Qb  The  vertical  planes  passing  through  R 
and  T are  one-half  inch  apart ; therefore  if  a one-hundred-pound 
weiglat  be  suspended  at  one-half  inch  from  R,  acting  as  a simple 
lever,  it  will  be  under  precisely  the  same  conditions  as  the  differ- 
ential lever  with  the  above  dimensions.* 


Section  III. — Fahrication. 

445.  FABRIC ATIOFT  OF  CAST-IROFT  GUNS.— The 
details  of  the  casting  of  a XY-inch  gun,  as  practiced  at  the  Fort 
Pitt  Foundry,  Pittsburgh,  Pa.,  will  be  taken  as  an  example,  f 

446.  The  Furnaces. — Two  reverberatory  air  furnaces  are 
used  for  melting  the  iron  of  which  the  gun  is  made,  the  draught 
being  produced  by  high  chimneys  instead  of  by  a blast.  Fig.  69 
represents  the  Fort  Pitt  Air  Furnace,  the  peculiarity  being 
that,  as  the  iron  melts,  it  runs  backwards  toward  the  bridge-wall, 
C ; the  crown  of  the  furnace  being  so  constructed  as  to  cause 
the  flame  to  impinge  against  the  surface  of  the  pool  of  melted 
metal,  while  at  its  greatest  temperature ; thus  it  is  melted  with- 
out coming  in  direct  contact  with  the  carbon,  as  in  the  blast- 

* See  a description  of  Kirkaldy’s  machmes  in  the  London  Mechanics'  Magazine 
of  the  9th  March,  1866. 

f Conamdr.  R.  F.  Bradford,  U.  S.  Navy. — Navy  Ordnance  Papers,  No.  3. 


152 


NAVAL  OKDNANCE  AND  GUNNERY. 


furnace  — where  the  fuel  aTid  fire  are  mixed  together.  Bitu- 
minous coal  is  used  in  these  furnaces. 

417.  In  the  Fig.  69,  A represents  the  metal-chamher,  being 


that  part  of  the  furnace  where  the  iron,  for  what  is  termed  a 
“ heat,'’’  is  placed.  The  bed  of  this  chamber  is  first  prepared 
by  covering  it  with  a layer  of  sand,  Avhich  is  hardened  down,  giv- 
ing it  at  the  same  time  the  desired  curve  ; then  boards  are  laid, 
upon  which  the  pigs  of  iron  to  be  melted  (or  charged)  are 
piled;  B repi-esents  the  fuel  chamber,  or  fireplace,  the  name 
passing  over  the  bridge-wall,  C,  and  through  the  metal  chamber 
on  its  way  to  the  chimney,  I)  ; ^ is  the  tap-hole ; X,  the  charg- 
ing-door, made  of  fire-brick  bound  together  by  iron  bands ; E 
is  the  ash-pit ; and  f,  the  grate-bars.  The  dotted  line  represents 
the  surface  of  the  metal  when  “ doicn^’’  or  melted. 

448.  In  the  charge  used  for  a XV-inch  gun,  the  greatest 
depth  of  metal,  when  down,  is  about  nine  inches,  exposing 
about  one  hundred  square  feet  of  surface  to  the  flame. 

It  is  very  necessary,  in  castiug  a lot  of  guns,  to  have  the  bed 


CAST  GUNS. 


153 


of  the  fiu’nace  prepared,  in  every  instance,  the  same  as  with 
the  standard  gun,  as  the  treatment  of  a given  charge  of  iron  may 
he  varied  by  the  manner  of  dressing  the  bed  of  the  furnace. 
By  exposing  the  same  amount  of  iron  in  a broad,  shallow  pool, 
it  is  more  eilectu  dly  brought  under  the  influence  of  the  flame 
than  when  collected  in  a narrow,  deep  pool. 

449.  Charging  the  Furnaces. — In  charging  the  furnace  for  a 
“ heat,”  the  ditferent  grades  of  iron  which  have  been  decided 
upon  are  weighed  and  piled,  in  the  proper  proportions,  in  the 
metal-chamber  of  the  furnace,  always  having  the  second-fusion 
iron  nearest  the  Are. 

450.  Fusions. — The  iron,  as  it  comes  from  the  smelting-fur- 
nace, is  termed  ‘■Faw pig,”  and  is  a first  fusion.  The  second- 
fusion  iron  (as  understood  by  founders)  is  produced  by  a com- 
bination of  raw  pig  and  second-fusion,  melted  in  an  ordinary 
fir-furnace,  and  then  run  out.  These  pigs  are  usually  of  a dif- 
ferent shape  than  the  raw  pig,  but  to  prevent  confusion,  and  at 
the  same  time  to  distinguish  different  second-fusion  irons  one 
from  another,  each  should  be  distinctly  marked  and  piled 
separately. 

451.  The  object  of  using  a second-fusion  iron  in  a casting  is 
to  obtain  greater  density  than  can  be  produced  from  the  raw 
pig  alone ; it  also  increases  the  tensile  strength.  (Art.  349.) 


452.  The  Charge.— In  casting  the  XV -inch  gun,  the  fur- 
naces were  each  charged  as  follows  : 

Bloomfield  raw  pig 21,143  lbs. 

Bloomfield  second  fusion  (red-dot) 13,214  “ 

Bloomfield  second  fusion  (red-cross) 2,043  “ 

37,000  “ 

Total  in  both  furnaces 74,000  “ 


The  second  fusion,  marked  ‘‘red-dot,”  consisted  of  the  fol- 
lowing combinations,  viz. : 

Bloomfield  raw  pig 50,000  lbs. 

Bloomfield  second  fusion 19,575  “ 

. Run  into  pigs  and  marked  “ red-dot  ” 69,575  “ 

The  proportions  of  the  other  grade,  marked  “ red-cross,”  are 
as  follows,  viz. : 

Bloomfield  raw  pig 29,410  lbs. 

Bloomfield  second  fusion 32,590  “ 

Run  into  pigs  and  marked  “red-cross”.  . ..62. 0(io  “ 


154 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  second-fusion  iron  used  in  these  combinations  is  pro- 
duced by  melting  two  parts  of  raw  pig  with  one  of  second  fusion- 

453.  Molding,  in  general  terms,  is  the  process  by  which  a 
cavity  of  the  form  of  the  gun  is  obtained,  by  embedding  a 
model  in  sand  and  then  withdrawing  it. 

454.  Moldhuj-composition. — The  sand  most  nsed  for  this 
purpose  is  a kind  of  loam,  which  contains  a sufficient  quantity 
of  clay  to  i-ender  it  moderately  cohesive  when  damp.  Sand, 
possessing  all  the  qualities  required  for  molding,  is  seldom,  if 
ever,  found  in  a state  of  nature;  but  when  the  requisite  cpiali- 
ties  are  known  the  materials  may  be  selected,  and  an  artificial 
composition  produced  without  difficulty.  The  sand  should  be 
principally  of  silex,  very  refractory,  and  of  the  kind  commonly 
called  sharp-sand.  When  not  sufficiently  refractory,  the  sand  is 
vitrified  by  the  high  temperature  of  the  melted  metal,  and  pro- 
tuberances are  found  upon  the  casting  which  are  not  easily 
removed. 

455.  The  method  of  preparing  the  molding-composition 
artificially,  varies  according  to  the  kind  of  casting  for  which  it 
is  to  be  used.  In  preparing  it  for  cannon,  great  care  is 
taken  to  introduce  the  exact  quantity  of  clay  required.  When 
too  little  is  used,  the  composition  is  not  sufficiently  adhesive ; 
when  too  much  is  used,  the  mold  is  injured  by  contraction  iii 
drying.  The  sand  is  first  carefully  sifted,  then  properly  mixed 
and  moistened  with  water  in  which  clay  has  been  stu-red ; the 
composition  is  considered  sufficiently  adhesive  when  it  will  retain 
its  form  after  having  been  taken  in  a moist  state  and  squeezed 
in  the  hand. 

45G.  The  same  composition  may  be  repeatedly  used  for  mold- 
ing, but  as  the  adhesive  property  of  the  clay  is  destroyed  by  the 
heat  to  wdiich  it  is  exposed  in  casting,  more  clay  must  be  added 
every  time,  in  the  same  manner  as  when  the  composition  is  first 
formed. 

457.  Models. — The  wmoden  model  is  technically  called  the 
pattern. 

Models  for  casting  should  be  made  of  one  or  several  pieces, 
according  to  the  form  of  the  mold  required.  When  the  form  is 
sucli  that  the  whole  model  can  be  withdrawn  from  the  sand  at 
once,  without  injuring  the  mold,  a single  piece  will  suffice;  but 
generally  the  model  is  composed  of  several  pieces,  so  fitted  that 
"they  can  be  put  together  in  succession  as  the  molding  progresses, 
and  finally  taken  apart  and  removed  by  piecemeal  when  the 
molding  is  complete. 

458.  The  Flask. — The  mold  is  formed  in  a case  of  cast-iron, 
called  a flash,  consisting  of  several  pieces,  each  of  which  has 


CAST  GUNS. 


155 


I 

1 

i 


156 


NAVAL  ORDNANCE  AND  GUNNERY. 


flanges  perforated  with  holes  for  screw-bolts  and  nuts,  to  unite 
the  parts  flrmly. 

In  casting  the  XY-inch  gun,  a circular  flask  (Fig.  TO)  is  used, 
consisting  of  live  upright  sections,  secured  together  by  clamps 
fitting  over  flanges,  AAA,  at  either  end  of  the  sections ; its 
thickness  is  one  inch,  and  it  is  pierced  Avith  holes.  (Art.  481). 

459.  Divisions  of  the  Flask. — The  breech,  or  loAver  section, 
BB,  is  made  of  sufflcient  length  to  cast  the  base  of  breech,  cascabel, 
and  square  knob ; the  ne^t  above,  CC,  is  tAventy-five  inches  in 
length  and  cylindrical,  being  the  part  which  embraces  the 
cylinder  of  the  gun ; the  next  is  the  trunnion-sections,  DD, 
fitted  Avith  trunnion-boxes  having  movable  plates  on  their  ends, 
that  the  trunnion  pattern  may  he  placed  and  removed  after  the 
mold  is  finished ; then  there  are  two  sections  above  this,  £E  and 
FF,  the  upper  being  about  three  feet  longer  than  the  required 
length  of  the  gun,  to  admit  of  a “ sinldng-lieadr 

The  entire  length  of  the  flask  is  tAventy  feet. 

460.  Pkocess  of  Molding. — The  pattern  is  in  five  sections, 
each  slightly  tapered,  that  the  mold  might  he  uninjured  in  its 
withdraAval.  The  average  thickness  of  sand  forming  the  mold 
is  about  eight  inches. 

461.  In  making  the  mold,  the  lower  section  is  placed  upon 
a plate  of  iron  in  an  upright  position  ; the  pattern  being  intro- 
duced and  centred,  the  space  hetAveen  the  pattern  and  the  flask 
is  then  filled  with  molding-sand,  using  thin  layers,  which  are 
rammed  uniformly  until  the  Avhole  of  that  section  is  complete. 
The  patterns  for  the  “ runners,”  ER,  and  their  branches,  h,  b,  h, 
are  introduced  as  the  Avork  progresses ; the  latter,  being  tapered, 
are  easily  removed. 

462.  After  the  mold  for  the  breech,  or  lower  section,  is 
finished,  the  next  section  of  the  flask  is  placed  upon  it  and 
secured,  the  pattern  for  which  is  introduced,  and,  being  fitted 
with  doAvels,  held  accurately  in  place.  The  molding  is  continued 
with  this  section  as  Avith  the  first,  and  when  completed  is  lifted 
off,  care  being  taken  not  to  break  the  mold  (the  pattern  being 
left  in  the  mold). 

463.  The  third  or  trunnion  section  is  then  placed  upon  the 
second,  the  model  being  adjusted  as  Avith  the  second,  and  the 
molding  is  continued  in  this  Avay,  until  the  whole  is  completed, 
thus  insuring  a perfect  mold  throughout,  free  from  irregulari- 
ties at  the  junction  of  the  sections. 

464.  The  patterns  are  then  Avithdrawn,  and  the  molds  fin- 
ished and  smoothed  about  the  lock-lugs,  sight-masses,  and  side- 
gates,  after  Avhich  it  is  placed  in  the  drying-oven,  the  two  lower 


CAST  Gims. 


157 


sections  being  clamped  together,  the  others  singly  ; and  -^hen 
thoroughly  dry,  withdrawn. 

465.  A wash  composed  of  pulverized  coke-cinders,  molasses, 
and  water  is  then  applied ; this  dries  qiiickly,  and  produces  a 
smooth,  hard  surface,  thus  preventing  the  molten  metal  from 
entering  into  the  sand  of  the  mold,  and  it  insures  a smooth, 
clean- coating. 

466.  The  Coee-bakkel; — The  core-barrel  (Fig.  71)  consists 
of  a water-tight  iron  tube,  AD,  about  fifteen  feet  long,  and 


Cap  uith  journal 
used  when  making 
Core. 


SEOTIOH  AT  A-U. 


Journal  and  Ring-bolt  put  in  I 
to  tui  n barrel  on  in  maldng  ® 

Core. 

Fig.  71. — Core-barreL 

three-fourths  of  an  inch  thick,  its  exterior  diameter  at  the  head 
being  twelve  inches,  and  tapering  one-fourth  of  an  inch,  at  the 
lower  extremity,  to  facilitate  its  withdrawal  after  the  cast. 

It  is  rounded  at  its  lower  end,  D,  and  fiuted  throughout  the 


158 


NAVAL  ORDNANCE  AND  GUNNERY. 


cylindrical  part,  to  allow  the  escape  of  gas  generated  by  tlie 
burning  of  the  composition  with  which  it  is  covered. 

467.  Pkepaeing  the  Coee. — To  prepare  the  core  for  cast- 
ing,  journals  (Pig.  71)  are  first  fitted,  at  either  extremity  of  the 
barrel ; it  is  then  placed  in  a horizontal  position  upon  an  iron 
truck,  being  supported  by  the  journals,  which  rest  in  bearings. 
AVhile  so  supported  it  is  easily  turned  by  means  of  a crank 
attached  to  one  of  the  journals,  and  is  first  wrapped  or  served 
with  white-hemp  stuff  (18-thread),  covering  that  portion  of  the 
barrel  which  comes  in  contact  with  the  molten  iron. 

468.  Over  this  a coating  of  molding-composition  is  applied 
quite  wet,  which  is  wrapped  with  twine,  to  insure  its  adhering. 
When  about  half  di-y,  the  outer  or  last  layer  of  composition  is 
applied,  which,  being  made  quite  sticky,  adheres  readily.  Great 
care  is  taken  to  have  the  surface  of  the  core  perfectly  smooth, 
and  the  composition  of  unifonn  thickness.  The  diameter  of 
the  core-barrel  for  a XV-inch  gun,  when  complete,  is  13.75 
inches  at  the  top,  and  slightly  tapered  at  the  bottom. 

469.  When  ready,  the  truck  supporting  the  core-barrel  is 
rolled  into  the  drying-oven,  and' when  perfect!}'  dry  removed; 
the  usual  time  required  being  eighteen  hours.  The  Composi- 
tion then  receives  a coating  of  coke-wash,  when  it  is  again 
j)laced  in  the  oven,  where  it  remains  until  thoroughly  dry. 

Upon  its  final  removal  the  journals  at  either  extremity  are 
removed,  being  replaced  by  the  regular  cap  on  top,  and  a tight- 
fitting  screw-plug  at  the  bottom,  which  is  covered  with  mold- 
ing-composition, and  dried  by  a fire  built  under  it. 

470.  The  Pit. — The  pit  (Fig.  70)  is  circular  in  fonn,  nine- 
teen feet  deep,  and  twelve  feet  in  diameter ; the  walls  are  of 
brick,  and  the  bottom,  an  iron  tank  of  one-half  inch  sheet-iron, 
extending  upwards  eight  feet. 

The  mouth  of  the  pit  is  provided  with  iron  covers,  made  to 
fit  closely  to  prevent  escaping  of  heat  from  the  fire  built  around 
the  flask. 

471.  Placing  xhe  Flask. — The  mold  being  thoroughly  dry, 
the  two  lower  sections,  clamped  together,  are  lowered  and  secured 
in  an  upright  position  in  the  centre  of  the  pit — a layer  of  sand 
having  been  previously  placed  in  the  bottom,  for  the  flask  to 
rest  upon  ; the  other  sections  are  lowered  singly,  and  secured  in 
their  places,  the  whole  being  braced  from  the  sides  of  the  pit  to 
retain  it  in  a vertical  position. 

472.  Cranes. — Cranes  are  employed  for  moving  cannon, 
molds,  and  other  heavy  masses  about  a foundry.  They  are 
fitted  Avith  cog-wheel  gearing  to  obtain  power  at  the  expense 
of  time,  and  are  often  worked  by  steam.  Care  must  be  taken 


CAST  GUNS, 


159 


to  give  great  sti*engtli  to  this  machine,  and  to  caiioe  its  motion 
to  be  easy  on  its  pivot.  When  properly  adjusted  a weight  may 
he  lifted  and  transported  from  one  point  to  another,  anywhere 
within  the  limits  of  the  circle  described  by  the  arm. 

473.  AnjtiSTixG  the  Core. — The  core  is  then  lowered  into 
the  mold  of  the  gun.  To  centre  and  secure  the  core-barrel  in 
position  it  is  necessaiy  to  have  a frame,  usually  termed  a 
“ spider to  support  and  hold  rigidly  in  place  the  core  when 
properly  centred. 

The  spider,  SS  (Fig.  70),  is  of  cast-iron,  about  two  and  one- 
half  feet  high,  having  three  legs,  each  of  wliich  having  a projec- 
tion at  the  bottom,  fitted  with  an  adjustable  screw,  which  rests 
upon  the  upper  flange  of  the  flask  ; there  is  also  a funnel  or 
sleeve  fitted  in  the  central  part  of  the  top,  through  which  the 
core-barrel  passes  and  fits  closely,  holding  it  firmly,  so  that  any 
movement  of  the  frame  will  produce  a change  in  the  position  of 
the  core. 

474.  The  Gauge,  for  centering  the  core,  consists  of  a long, 
wooden  rod,  on  the  end  of  which  a piece  of  board  is  fixed  at 
right-angles,  and  on  this  board  a light  is  placed. 

The  length  of  this  projecting  board,  previously  determined, 
is  the  distance  the  core  should  be  from  the  mold  when  in  the 
centre. 

Having  adjusted  the  core  in  the  mold,  by  means  of  the 
screws  fitted  in  the  legs  of  the  spider,  it  is  secured  firmly  by 
clamps,  FI  (Fig.  70),  made  to  fit  over  the  top  of  the  frame  and 
under  the  flange  of  the  flask. 

475.  Meeting  down  the  Charge. — The  mold  and  core-bar- 
rel being  in  readiness,  and  the  furnaces  charged,  the  fires  are 
started  and  regulated  so  that  the  iron  will  be  “ down  ” in  both 
furnaces  at  about  the  same  time. 

Particular  attention  is  paid  to  the  manner  of  firing,  that 
it  be  uniform  and  steady ; also  that  the  fires  be  kept  clean  to 
produce  not  only  the  best,  but  uniform,  results. 

The  length  of  time  required  to  obtain  complete  fusion  of 
the  charge  depends  in  a great  measure  upon  the  state  of  the 
atmosphere,  etc.,  being  from  five  to  eight  hours. 

476.  When  nearly  down^’’  it  is  necessary  to  work  or  pud- 
dle it,  that  any  lumps  or  balls  of  unmelted  iron  may  be  brought 
in  contact  with  the  flame.  This  is  done  by  inserting  long  iron 
rods  or  green  saplings  in  the  air-holes  of  the  metal-chamber. 
Saplings  are  preferred,  as  the  steam  generated  from  the  sap  in 
the  wood  causes  the  molten  iron  in  the  pool  to  boil,  and  the  more 
dense  iron  at  the  bottom  is  mixed  with  that  of  the  surface, 
while  many  of  the  impurities  are  dispelled  at  the  same  time. 


160 


NAVAL  ORDNANCE  AND  GDNNEET. 


477.  When  the  charge  is  “clown”  specimens  are  taken  out 
to  ascertain  if  the  iron  is  in  proper  condition,  or  sufficiently 
“ IvKjli  ” (Art.  351) ; that  is,  sntiiciently  decarbonized  ; these  spe- 
cimens are  run  in  dry-sand  molds,  and  are  about  six  inches  in 
length,  varying  in  size  from  one-quarter  of  an  inch  to  one  inch 
square.  When  cold  they  are  broken,  and  the  appearance  of  the 
fracture  indicates  whether  the  iron  is  sufficiently  ’■'■high''  (Art. 
356).  The  three-cpiarters  of  an  inch  specimen  is  required  to  he 
well  mottled. 

478.  As  the  density  and  tensile  strength  of  the  iron  depends 
in  a great  ineasui’e  upon  the  “highness  ” to  which  it  is  brought, 
extreme  care  is  required  in  this  operation.  Where  the  first  spe- 
cimens proved  are  unsatisfactory,  the  iron  is  kept  in  fusion  still 
longer,  during  which  time  it  is  puddled  v/ith  green-poles. 

476.  Tapping  the  Fuknace. — When  eveiy thing  is  in  readi- 
ness the  furnaces  are  tapped,  and  the  molten  metal  conducted 
by  runners  or  troughs  coated  with  fire-clay  directly  to  the  side- 
gates  of  the  mold,  EE.  It  flows  into  these  and  down  to  the 
bottom,  entering  the  mold  by  branch-gates,  b,  b,  b,  at  intervals 
of  one  foot  apart  from  bottom  to  muzzle. 

Tlie  branch-gates  are  cut  so  that  the  metal  will  enter  the 
mold  in  a direction  toward  the  axis,  upward,  care  being  taken 
to  keep  the  molten  iron  after  it  enters  the  mold  well  stirred 
with  long  poles  to  prevent  scoria  from  entering  the  trunnion- 
holes,  and  also  to  assist  in  mixing  the  metals  from  the  different 
furnaces. 

480.  When  the  mold  is  nearly  full  the  tap-holes  are  stopped, 
and  the  surface  of  the  metal  in  the  gun-head  covei-ed  by  a layer 
of  pulverized  charcoal,  to  prevent  its  chilling.  The  time  of  till- 
ing the  mold  is  about  fourteen  minutes. 

The  surplus  iron  remaining  in  the  furnaces  is  run  into  pigs, 
but  is  not  used  again  for  gun-metal. 

481.  Heating  the  Pit. — During  the  casting,  the  gas  which 
is  generated  and  passed  out  through  the  holes  in  the  flask  is 
ignited  by  dropping  small  quantities  of  molten  metal  into  the 
pit,  and  as  soon  after  the  “ cast  ” as  possible,  a fire  is  built  in 
the  pit,  about  the  bottom  of  the  flask — wood  and  bituminous 
coal  being  used  in  sufficient  quantities  to  burn  four  or  five 
days ; the  mouth  of  the  pit  being  covered,  after  the  mass  is 
thoroughly  ignited. 

482.  Cooling  the  Casting. — The  water  for  cooling  is  taken 
from  a hydrant,  where  the  supply  is  constant  and  uniform,  the 
connections  being  made  by  rubber  hose.  It  is  conducted  to  the 
bottom  of  the  core-barrel  by  means  of  a copper  tube,  one  and  a 
half  inches  in  diameter,  TT  (Fig.  70).  This  tube  passes  through 


CAST  GUNS. 


161 


a water-tiglit  joint  in  the  centre  of  the  cap,  and  extends  to 
vrithin  a few  inches  of  the  bottom  of  the  barrel ; being  open  at 
its  lower  end,  the  water  passes  ont  and  ascends  through  the 
aiinidar  space  between  the  tubes,  and  is  discharged  from  the 
core-barrel  at  a point  above  the  casting,  Y. 

483.  The  water  for  cooling  the  core  is  started  before  the 
furnaces  are  tapped,  and  allowed  to  run  through  the  barrel,  and 
off  by  the  discharge-pipe,  Y,  Y,  to  ascertain  if  every  part  is  per- 
fectly tight ; it  continues  thus  to  circulate  until  the  core  is  re- 
moved, at  about  the  rate  of  forty  gallons  per  minute. 

484.  Withdrawing  the  Core-harrel. — This  is  done  about 
eighteen  hours  after  the  casting,  as  soon  as  the  metal  becomes 
sufficiently  cool  to  permit  of  its  removal.  The  withdrawal 
causes  no  delay  or  trouble,  as  the  rope  with  which  it  is  wrapped 
is  consumed,  and  therefoi’e  leaves  the  barrel  detached  from  the 
composition  surrounding  it,  the  latter  adhering  to  the  bore  of 
the  gun. 

485.  Cooling  log  air. — After  the  withdrawal  of  the  core-bar- 
rel the  cooling  is  continued  by  forcing  a continuous  stream  of 
air  into  the  cavity  thus  left,  by  means  of  a rotary  blower,  driven 
by  a small  steam-engine,  the  air  being  conducted  from  the 
blower  to  the  gun  through  an  eight-inch  sheet-iron  pipe,  which  is 
introduced  into  the  bore  and  to  within  one  calibre  of  the  bottom. 

486.  A record  of  the  rate  of  cooling  is  kept  by  noting  at 
regular  intervals  of  time  the  temperature  of  the  water  or  air  on 
entering  and  leaving  the  core.  When  the  temperature  of  the 
air  in  the  bore  is  nearly  down  to  that  of  the  outside  atmosphere, 
the  blower  is  stopped,  and  the  pipe  removed. 

Time  of  Cooling. — The  time  of  cooling  is  about  eight  days. 

For  XY-iuch  guns  it  usually  varies  from  seven  to  nine 
days,  depending  mainly  upon  the  temperature  of  the  air  and 
the  speed  of  the  blower. 

487.  Removestg  the  Casting. — The  gun  is  hoisted  from  the 
pit  ten  days  from  the  time  of  casting.  Preparations  for  re- 
moving the  ffask  commence  the  day  before. 

Transporting-lugs  are  cast  on  the  sinking-head,  to  which 
slings  are  attached  for  hoisting  and  landing  the  casting  in  the 
foundry,  where  all  irregularities  are  chipped  off,  and  the  sur- 
face thoroughly  cleaned  of  sand  or  foreign  substances,  and  pre- 
pared for  the  lathe. 

Weight  of  rough  casting,  including  sinking- 


head,  etc 66,000  lbs. 

Weight  of  rough  gun. ...  61,000  “ 

Weight  of  finished  gun 43.000  “ 


488.  Condition  of  the  Casting. — This  mode  of  casting,  by 

11 


163 


NAVAL  ORDNANCE  AND  GUNNERY. 


means  of  side-gates,  is  resorted  to  in  order  to  preserve  the  form 
of  the  mold.  If  the  metal  was  conducted  into  the  upper  open- 
ing of  the  ixiold  itself,  its  fall  upon  the  sides  and  bottom  would 
injure  their  forms. 

The  condition  of  the  casting  in  reference  to  smoothness 
depends  in  a great  measure  upon  the  state  of  the  mold  when 
the  metal  is  run.  It  should  be  perfectly  dry  and  hard,  otherwise 
the  metal  mixes  with  the  sand,  and  adheres  in  clumps,  produc- 
ing a I’ough  and  irregular  casting,  the  cleaning  of  which  is  a 
dithcult  and  laborious  job. 

489.  TIeading-lathe. — The  easting  is  next  placed  in  what 
is  called  the  '■^heading-lathe  (Fig.  72),  where  it  is  prepared  for 
the  horing-lathe.  The  cascab el-bearing,  base  of  breech,  and  a 


section  of  the  chase  are  all  turixed  down  to  finished  dimensions 
while  in  this  lathe,  as  the  chase  and  rounded  part  of  the  cascabel- 
knob  form  the  bearings  for  the  boring-lathe. 

The  cut  at  the  muzzle,  or  place  Avhere  the  sinking-head  is 
to  be  broken  off,  is  also  made  in  this  lathe. 

A (Fig.  72)  represents  the  muzzle-ring  with  adjustable 
screws;  B,  the  bearing  in  which  the  muzzle-ring  revolves;  C, 
the  chuck,  or  mortise,  into  which  the  square  knob  of  the  casca- 
bel  is  inserted  and  secured  ; D,  the  tools  or  cutters  with  rests. 

The  bearing  in  which  the  muzzle-ring  revolves  is  a heavy  cast- 
ing, the  bottom  of  which  fits  into  grooves  in  the  rack,  andean  be 
moved  to  or  from  the  chuck,  being  adaptable  to  long  or  short  guns. 

400.  Ad.justmext  ix  Lathe. — The  gun  is  lowered  into 
place,  the  square  knob  in  rear  of  the  cascabel  fitting  into  the 
chuck,  while  the  muzzle  is  introduced  and  projects  several 
inches  beyond  the  face  of  the  muzzle-ring,  in  which  position  it  is 
approximately  centred,  and  held  firmly  in  place  by  adjustable 
screws  in  the  chuck  and  muzzle-ring. 

491.  The  breech  is  adjusted  by  placing  a shaiqx-pointed  in- 
strument in  the  rest,  and  bringing  it  in  contact  with  the  surface 
of  the  easting  near  the  base-line,  and  while  turni  112:  the  gun — 
which  is  done  by  machinery — -the  screws  in  the  chut^c  are  moved 
nntil  coincidence  of  the  line  around  the  gim  is  obtained. 


CAST  Guisrs. 


163 


492.  At  the  muzzle  a bar  of  iron  is  laid  upon  blocks,  so 
that  it  shall  be  just  inside  the  bore,  and  nearly  in  contact  with 
its  interior  siu’face.  As  the  gun  turns,  the  distance  between  this 
point  and  the  metal  of  the  bore  is  observed,  and  equalized  ap- 
proximately, by  the  screws  in  the  muzzle-ring  beariug. 

493.  A Avooden  disk  turned  to  fit  the  bore  accurately,  bear- 
ing a string  attached  to  its  centre,  is  then  pushed  to  the  bottom 
of  the  bore,  and  made  to  assume  a position  in  a plane  perpen- 
dicular to  its  axis.  The  string  from  the  centre  of  the  disk  is 
long  enough  to  reach  some  distance  outside  of  the  muzzle  ; the 
outer  end  being  made  fast  to  an  upright  the  same  height  as  the 
inner  end  or  centre  of  disk  ; the  string  is  now  hauled  perfectly 
taut,  and  the  gun  again  tuimed,  a square  being  placed  upon 
blocks  about  one  foot  in  front  of  the  muzzle,  close  to  the  string ; 
and  as  the  gun  revolves,  the  distaiiee,  if  any,  which  the  string 
deA'iates  from  the  square  is  observed  and  corrected  by  again 
moving  the  screws  in  the  muzzle-beariug. 

494.  When  properly  centred,  the  string  will  remain  in  the 
same  position  in  the  square  and  be  the  same  distance  from  the 
interior  surface  of  the  gun,  throughout  an  entire  revolution, 
showing  that  the  axis  of  the  gun  and  lathe  coincide. 

"With  the  holloAV  cast-gun  it  is  necessary  that  it  shoidd  be 
centred  from  the  bore,  as  it  sometimes  happens  that  its  axis 
does  not  coincide  with  the  axis  of  the  casting,  which  is  one  rea- 
son for  casting  them  above  the  true  size,  to  admit  of  being  fin- 
ished by  the  interior,  or  so  that  the  axis  of  the  cast  bore  shall 
coincide  Avith  that  of  the  gun  when  turned. 

495.  Measuring  the  Casting. — The  casting  is  next  meas- 
ured, taking  diameters  at  the  principal  points,  length  of  the 
casting,  sinking-head,  diameter  and  length  of  trunnions,  distance 
from  centre  of  trunnions  to  base-line,  size  of  lock  and  sight- 
masses  ; also  excess  of  metal  over  finished  dimensions  at  points 
ten  inclies  apart,  commencing  at  forty -five  inches  ahead  of  base- 
line. 

Shoidd  cavities  or  defects  of  any  kind  he  discovered,  their 
depth  and  full  extent  will  he  ascertained  and  noted,  thus  pre- 
venting useless  subsequent  labor  in  case  they  exceed  the  limits 
of  toleration. 

496.  Turning  down  the  Casting. — The  gun  being  centred, 
the  turning  commences  at  the  muzzle ; this  is  done  by  placing 
a tool  in  the  rest,  Avhich  is  brought  in  contact  with  the  surface 
at  the  desired  point,  the  metal  being  turned  off  as  the  gun  re- 
volves. The  rest^  or  support  which  holds  the  tool,  is  arranged 
to  move  in  two  directions,  one  toAvard  the  gun,  or  at  right  an- 
gles to  the  axis  of  the  lathe,  by  which  means  the  depth  of  cut  is 


16i 


NAVAL  ORDNANCE  AND  GUNNERY. 


regulated,  and  the  other  in  line  parallel  with  the  axis,  that  is, 
from  muzzle  to  breech. 

497.  This  last  movement  is  effected  by  means  of  s,fecd,  the 
motion  being  given  by  a fork  attached  to  one  of  the  trunnions, 
and  at  every  revolution  of  the  gun  the  rest  is  made  to  advance. 

The  first  cut  is  usually  an  inch  deep,  commencing  at  the 
muzzle  where  the  sinking-head  is  to  be  cut  off  and  extending 
thirty  inches  towards  tlie  trunnions. 

The  second  and  third  cuts  are  commenced  at  the  same  point 
as  the  first,  and  are  about  one  and  one-eightli  of  an  inch  deep  ; 
increasing  as  the  tool  advances  in  the  gun,  other  cuts  are  made 
until  the  metal  is  reduced  to  the  finishing  diameter. 

498.  Eemoving  the  Sinkixg-iiead. — The  cut  at  the  muzzle, 
or  the  place  where  the  “sinking-head”  is  to  be  broken  off,  is 
next  made ; its  depth  is  usually  about  seven  inches  or  to  within 
three  or  four  inches  of  the  cast  bore. 

The  gun  is  now  taken  from  the  lathe,  and  the  “ sinking- 
head  ” broken  or  wedged  off,  at  which  time  the  appearance  of 
the  metal  at  the  fracture  should  be  examined  as  to  color,  form, 
and  size  of  crystals,  texture,  and  whether  sharp  to  the  touch  ; 
it  is  also  necessary  to  ascertain  its  degree  of  hardness,  and  how 
the  metal  works  under  the  tools,  in  the  different  stages  of  its 
fabrication  ; all  of  which  should  be  duly  noted  and  form  part 
of  the  record  of  the  gun. 

499.  Cu'mxG  out  Specimens. — Three  specimens  for  densi- 
tj,  tensile  strength,  etc.,  are  taken  from  the  face  of  the  “ sink- 
ing-head,” next  the  muzzle,  at  points  equally  distant  from  each 
other  around  the  circle  and  as  near  as  possible  to  the  outer  crust 
of  the  casting  (about  one-fourth  of  an  inch),  the  axis  of  the  sam- 
ple being  parallel  to  the  axis  of  the  gun.  These  specimens  are 
of  the  standard  size,  and  are  marked  on  each  end  with  the  letter 
II,  to  denote  head-specimens ; also  number  of  gun  from  which 
taken,  and  the  number  of  specimen.  (Art.  3S0.) 

500.  IloRixG-LATUE. — Tliis  lathe  (Fig.  73)  consists  of  the 


rack,  EE,  two  journals,  AA,  and  the  boring-rod,  B,  the  supports 


CAST  GUNS. 


165 


of  wliicla  rest  upon  tlie  rack,  and  are  of  suck  a heiglit  tliat  the 
axes  of  the  journals  and  horing-rod  shall  be  in  the  same  hori- 
zontal plane. 

501.  The  gun  while  in  the  lathe  rests  in  the  journals  at  the 
cascabel  bearing  and  chase;  the  metal  at  these  points  having 
been  turned  down  to  the  finished  size  while  in  the  heading- 
lathe,  the  square  knob  or  cascabel  is  secured  in  the  chuck  by 
tightening  the  screws  equally  in  all  directions. 

502.  Adjustment  iisr  the  Latue. — The  boring-rod  is  first 
introduced  a short  distance  into  the  bore  of  the  gun,  and  the 
space  between  the  exterior  surface  of  the  boring-rod,  and  the 
exterior  surface  of  the  gnn  at  the  muzzle,  observed.  For  this 
purpose  a thin  wooden  gauge  is  used,  pointed  at  one  end  and 
having  a notch  at  the  other,  which  takes  the  outer  surface  of 
the  gun  at  the  muzzle,  the  gauge  being  laid  on  the  face  of  the 
mu^&zle,  and,  of  course,  perpendicular  to  the  axis  of  the  bore. 
As  the  gun  revolves,  the  distance  above,  below,  and  on  either 
side  is  observed,  thus  verifying  the  perfect  concentricity  of  the 
axis  of  the  gun  at  the  muzzle. 

The  adjustment  is  completed  at  the  breech,  by  slackening 
the  bolts  at  the  cascabel  bearing,  leaving  it  free  to  move  on  the 
rest ; and  should  any  lateral  motion  be  perceptible,  it  is  correct- 
ed by  adjusting  the  screws  in  the  chuck,  after  which  the  con- 
centricity is  complete  from  breech  to  muzzle. 

503.  Boring. — In  boring,  the  first  tool  or  cutter  used  is 
fourteen  inches  in  diameter,  being  secured  on  the  end  of  the 
boring- rod,  or  arbor,  C,  which  is  made  to  advance  by  machinery 
as  the  gun  revolves,  until  arriving  at  the  bottom  of  the  cylin- 
drical part  of  the  bore.  The  chamber  is  next  roughed  out,  and 
then  the  “ reamer,”  or  finishing-tool  (fifteen  inch),  for  the  bore 
is  used  ; and  lastly  the  chamber  “ reamer.” 

50i.  During  the  process  of  boring,  the  turning  continues, 
and  the  exterior  is  finished,  except  between  the  trunnions  and 
about  the  lock  and  sight-masses ; the  former  being  planed  off 
by  a machine  for  the  purpose,  and  the  latter  reduced  by  chip- 
ping and  filing.  To  insure  a smooth  surface  in  the  bore,  all 
the  work  on  the  exterior  surface  of  the  gun  is  suspended  while 
the  reamer,  or  finishing-tool,  is  being  used. 

505.  The  boring  being  completed,  the  cylinder-guage  is  in- 
serted before  removing  the  gun  from  the  lathe,  to  ascertain  if  it 
passes  freely  to  the  bottom  of  the  bore ; the  chamber-reamer 
should  also  be  measured  after  use  in  each  gun,  and,  if  found 
correct,  the  gun  is  moved  from  the  lathe. 

506.  Trunnion-lathe. — The  gun  is  next  placed  in  the 


166 


NAVAL  ORDNANCE  AND  GUNNERY. 


trunnion-lathe,  which  consists  of  the  rack,  two  journals,  and  the 
trunnion-head,  or  shaft. 

The  gun  is  placed  in  the  journals,  which  are  of  such  a height 
that  the  axis  of  the  gun,  when  properly  adjusted,  shall  be  level, 
the  gun  being  supported  at  the  chase  and  cascabel. 

507.  The  trunnion-head  consists  of  a hollow  shaft  in  which 
the  cutters  are  placed,  and  is  supported  irpon  a rack  previously 
placed  at  right  angles  to  the  axis  of  the  gun,  and  of  such  a 
height  that  it  shall  he  in  the  same  horizontal  plane  as  the  axis 
of  the  gun . 

508.  In  turning  and  finishing  the  trunnions,  the  hollow 
shaft  of  the  trunnion-machine  is  made  to  revolve  about  the 
trunnion,  the  gun  being  stationary ; and,  as  the  turning  pro- 
gresses, the  shaft  moves  on  its  rack  towards  the  gun,  its  speed 
being  regulated  as  circumstances  require.  One  trunnion  and 
rim-base  being  finished,  the  gun  is  turned  over,  bringing  the  other 
trunnion  in  the  same  position  as  the  first,  and  is  turned  in  like 
manner. 

509.  The  Planing-machine. — The  metal  in  excess  between 
the  trunnions  is  removed  by  the  planing-machine  (Fig.  TI), 


which  is  placed  on  the  side  opposite  the  trunnion-machine,  and 
is  so  arranged  that  the  movable  point  in  which  the  cutter  is  se- 
cured, A,  traverses  forward  and  back  in  a horizontal  plane 
over  that  portion  of  the  gun  between  the  trunnions  that  has  not 
been  turned  down.  The  cutter  is  secured  in  a spring-set,  B,  by 
which  means  it  cuts  only  while  moving  forward,  the  gun  being 
ttirned  the  tvidth  of  the  cut  after  each  passage  of  the  planer. 

510.  The  desired  curve  of  metal  is  obtained  by  introducing 
a guide-plate  of  tlie  proper  form,  C,  in  rear  of  the  cuttei’-rest. 

After  the  planing  is  finished,  the  gun  is  removed  from  the 


CAST  GUNS. 


167 


lathe,  and  placed  upon  the  skids,  where  the  surplus  metal  about 
the  rim-bases,  lock,  and  sight-masses  is  reduced  by  chipping,  and 
finished  by  hand. 

511.  Cutting-  PIole  for  Elevating-screw. — The  gun  being 
carefully  levelled,  and  the  trunnions  placed  horizontal,  the  po- 
sition of  the  centre  of  the  serew-hole,  which  in  the  guns  of  the 
Dahlgreii  pattern  is  tangent  to  the  radius  of  the  breech,  is 
marked  on  the  neck  of  the  cascabel  with  a centre-punch. 

512.  The  Boring  and  Screvycutting  Machine,  which  is  a con- 
venient, portable  hand-drill  press,  is  then  placed  on  the  cascabel, 
the  boring-shaft  inserted  in  the  hollow  leading-bar,  and  its  mova- 
ble centre  placed  in  the  mark.  The  instrument  is  then  set  verti- 
cal, by  a spirit-level,  on  the  cogged  driving-wheel  and  the  four 
pairs  of  set-screws  on  the  clamp-head  embracing  the  cascabel. 

513.  The  centre  is  then  removed,  and  a drill  inserted  in  the 
lower  extremity  of  the  boring-shaft,  which,  being  held  firmly  by 
a shoulder  and  turned  by  a four-armed  wrench,  while  pressed 
up  to  the  metal  by  slowly  turning  the  cogged  driving-wheel, 
cuts  the  hole.  This  is  successively  enlarged,  by  two  or  more 
counter-bits,  to  the  size  of  the  body  of  the  screw. 

The  cutter  is  then  inserted  in  the  leading-bar,  and  the  thread 
cut. 

514.  Drilling  the  Yent. — The  proper  position  for  the  ex- 
terior orifice  of  the  vent  having  been  determined  and  marked 
upon  the  base-line,  the  drill  is  set  at  the  required  angle  by  the 


\84T'  \70& 


yent-guide  (Art.  566),  and  held  in  position  by  a frame  of  cast- 
iron,  which  is  secured  on  the  gim. 


1G8 


NAVAL  ORDNANCE  ANT)  GENTNERT. 


After  the  vent  is  fairly  started,  the  g;im  is  tirmed  over,  that 
the  cutting  may  not  obstruct  the  drill.  The  left  vent  is  simply 
indicated,  being  bored  two  inches. 

The  scpiare  knob  of  the  cascabel  is  now  brohen  off  and  the 
end  of  the  cascabel  rounded  and  finished ; also  the  foundry 
number  is  stamped  on  the  right  rim-base  in  one-fom-th-ineh 
figures. 

515.  Marking  Guns. — Guns  for  the  ISfaval  service,  received 
by  authority  of  the  llureau  of  Ordnance,  are  to  be  marked  in 
the  following  manner,  viz. : 

On  the  cylinder,  in  the  line  of  sight  near  the  sight-mass,  all 
accepted  guns  are  to  have  stamped  an  anchor  two  inches  long. 

On  the  base  ring  or  line,  the  initials  of  tne  foundry,  the 
register  inamber,  and  weight  of  gun  in  pounds. 

On  the  right  trunnion,  the  calibre  and  year  of  fabrication. 
On  the  left  trunnion,  the  letter  P,  and  the  initials  of  the  In- 
specting Officer ; all  the  above  in  one-inch  letters. 

Oil  the  upper  jaw  of  the  cascabel,  the  preponderance  in 
pounds  to  be  stamped  lightly  with  half-inch  figures. 

On  the  end  ot  the  upper  jaw,  the  cascabel  block,  and  head  of 
pin,  the  foundry  number  in  quarter-inch  figures. 

The  foundry  number  is  also  to  be  marked  on  the  right  rim- 
base. 

Guns  rejected  for  imperfections  of  any  kind  will  have  the 
letter  0 stamped  on  the  anchor,  so  as  to  partiallv  obliterate  it. 

510.  PABEICATIOJI  OF  BEOAZE  IlOAVITZEES.— A 
model  or  pattern  of  the  gun  is  first  prepared ; to  do  this  it  is  first 
necessary  to  lay  down  on  paper  an  exact  draAviug  of  the  gun  de- 
sired ; showing,  on  a convenient  scale,  its  general  appearance  and 
the  relative  proportions  of  its  different  parts,  both  exterior  and 
interior  ; the  full  dimensions  being  put  down  opposite  each  part. 

517.  A drawing  of  the  gun  is  now  made  on  a smooth  board, 
full  size,  the  dimensions  taken  from  the  draught,  but  laid  down 
by  a rule,  Avhichfis  larger  than  an  ordinary  one  by  0.15  of  an 
inch  to  the  foot,  which  alloAvs  for  the  shrinkage  of  the  metal  in 
cooling. 

518.  Two  pieces  of  clear,  well-seasoned  white  pine  are  se- 
lected of  such  proportions  that,  Avheu  joined,  they  will  form  a 
sqiiare  piece  of  timber,  considerably  larger,  and  of  greater  di- 
ameter, than  the  gun  itself. 

The  two  corresponding  faces  being  smoothed,  so  that  a 
perfect  junction  may  be  formed,  four  holes  are  made  in  the 
face  of  one,  Avhile  corresponding  pins,  termed  steadijing-pim^ 
are  fitted  in  the  face  of  the  other ; this  is  for  the  purpose  of 
insuring  the  vCxaet  adjustment  of  the  parts  while  molding. 


CAST  GUXS. 


169 


The  pieces  are  then  joined  face  to  face,  the  extremities 
rounded  otf,  and  iron  bands  driven  over  the  ends,  for  the  pur- 
pose of  uniting  them  tirmlv. 

Thus  fitted,  the  wliole  is  carefully  adjusted  in  a lathe,  so 
that  the  axis  shall  fall  directly  in  the  plane  dividing  the  two 
parts.  It  is  then  turned  down  to  the  required  form.  _ 

519.  The  pattern  consists  of  three  parts:  the  model  of  the 
gun  itself,  the  sinking-head,  and  knob  of  the  cascabel,  which  is 
enlarged  to  form  a square  projection  by  which  the  piece  can  be 
held  while  being  turned  and  bored. 

When  the  pattern  is  detached  from  the  lathe  these  parts 
are  separated  with  a saw.  Pieces  of  wood  representing  tlie 
sight-masses,  the  lock-lug,  and  the  loop  are  tacked  on  in  their 
proper  places,  and  the  whole  is  sand-papered  and  varnished. 
The  pattern  is  now  complete,  and  the  parts  will  represent  the 
appearance  of  two  semi-cylindrical  bodies  exactly  similar  in  size 
and  shape. 

520.  The  Flask  is  a long,  rectangular  box,  P (Fig-  T6), 
made  of  iron-plates  bolted  together,  the  top  and  bottom  ones, 
whicli  are  movable  and  called  lids^  being  of  one-quarter  inch 
wrought-iron  and  the  sides  of  half-inch  cast-iron. 

It  consists  of  two  equal  parts,  each  of  which  is  large  enough 
to  contain  half  the  mold ; these  parts  are  each  fitted  with  a 
flange,  extending  entirely  around  the  flask,  and  perforated  with 
holes  for  screw-bolts  and  nuts  to  unite  the  two  parts  firmly. 

They  are  also  fitted  with  joimnals  at  the  ends  for  conveni- 
ence in  suspending  them ; and  with  eye-bolts  for  the  pur- 
pose of  moving  them  about,  lowering  the  flask  into  the  pit, 
etc. 

The  head  of  the  flask  has  a large  hole  and  two  small  ones, 
in  wliich  to  pour  the  metal  and  to  permit  the  escape  of  gases. 
The  flask  has  strengthening  pieces  at  different  places,  and  inside 
is  divided  into  compartments  by  iron  plates  having  a score  cut 
in  them  to  receive  the  pattern.  These  plates  serve  to  make 
the  mold  more  compact. 

521.  Moldixg. — A smooth,  flat  board,  whose  dimensions 
are  a little  larger  than  the  flask,  is  placed  on  the  ground,  and 
the  half-model  is  placed  upon  it  flat  side  down.  The  corre- 
sponding half-flask  with  its  lid  removed  is  then  placed  around 
it  and  clamped  to  the  board.  Molding-composition  is  intro- 
duced in  small  quantities  at  a time  and  rammed  compactly 
around  the  model.  This  is  continued  until  the  flask  is  fllled  ; 
the  lid  is  then  bolted  on,  the  flask  hoisted,  turned  over,  and 
again  deposited  on  the  ground  with  the  lid  down.  The  board 
is  then  undamped ; the  face  of  the  mold  then  brushed  off,  and 


170 


NAVAL  ORDNANCE  AND  GUNNERY. 


sprinkled  with  a kind  of  wdiite  sand,  called  parting-sand,  to 
kee]3  the  two  parts  of  the  mold  from  sticking  together. 

The  other  ha  If -model  is  then  placed  in  position  on  top  of 
the  first,  and  tlie  corresponding  half-flask  with  its  lid  removed 
secured  in  place  to  the  under  one. 

The  sand  is  again  introduced  and  rammed  compactly 
around  the  upper  half-model  as  before,  the  steadying-pins  hold- 
ing it  firmly  in  jflace  ; when  the  flask  is  filled  the  second  lid  is 
bolted  on. 

The  half-flasks  are  now  separated  and  each  is  found  to  con- 
tain one-half  of  the  mold  with  the  corresponding  parts  of  the 
model  embedded. 

The  latter  are  then  carefully  withdrawn  and  all  imperfec- 
tions on  the  face  of  the  mold  are  repaired,  w’hen  it  is  coated 
with  a composition  of  brick-dust,  pipe-clay,  molasses,  and  water, 
which  gives  the  interior  of  the  mold  a smooth,  hard  surface. 

522.  A runner  is  made  on  one  side  with  a single  branch  at 
the  bottom  for  the  purpose  of  introducing  the  molten  metal. 
This  channel  is  made  by  embedding  a rod  in  the  sand  between 
the  two  half -flasks  in  molding  the  piece.  The  branch  runner 
enters  the  mold  in  an  oblicpie  direction. 

The  entrance  of  the  metal  to  the  mold  at  its  bottom  is  at 
an  angle  which  gives  a rotary-motion  to  the  liquid,  the  effect 
being  to  produce  a depression  in  the  centre  and  a gravitation  to 
it  of  all  scoria. 

A narrow  channel  is  cut  in  the  molding-composition  some- 
what larger  than  the  small  hole  in  the  head  of  the  flask,  and 
leading  from  it  to  the  channel  left  by  the  rod.  Another  nar- 
row channel  is  cut  from  the  other  small  hole,  intersecting  the 
mold  about  a foot  from  the  top,  by  which  the  height  of  the 
metal  in  the  mold  can  be  ascertained  during  the  casting. 

523.  The  drying-oven  is  a rectangular  apartment  built  of 
brick,  with  an  arched  roof  and  iron  doors,  having  tracks  led 
into  it  for  the  ears  upon  which  the  flasks  rest.  It  is  heated  by 
an  open  fireplace  which  is  fed  from  the  outside  with  coal. 

521.  Drying  the  JSLold. — The  half-flasks  are  securely  bolted 
together,  when  the  whole  is  placed  upon  a car  and  run  into  the 
oven  or  drying-room,  where  it  is  allowed  to  remain  three  or 
four  days,  or  until  it  is  perfectly  dry.  The  temperature  of  the 
oven  ranges  from  200°  to  250°  F. 

525.  The  Pit. — The  pit  is  of  a circular  form  and  lined 
throughout  with  water-proof  cement.  It  is  situated  directly  in 
front  of  the  furnace,  and  is  fitted  with  an  adjustable  apparatus 
for  receiving  the  flask,  and  sustaining  it  in  an  upright  position. 

526.  Plachstg  the  Flask. — The  flask  is  lowered  uito  the  pit, 


CAST  GUNS. 


in 


breecli  down,  until  tlie  upper  end  is  about  twelve  inches  below 
the  spout  at  the  mouth  of  the  furnace ; it  is  then  secured  in  this 
position,  and  boards  are  placed  over  the  mouth  of  the  pit  for 
the  convenience  of  the  founder. 

527.  Chaegestg  the  Fuehace. — A reverberatory  furnace  is 
used. 


The  proportions  of  the  metals  selected  for  this  species  of 
bronze  are  such  as  to  produce  the  toughest  and  most  inde- 
structible alloy.  It  consists  generally  of  ninety  parts  of  copper 
and  ten  of  tin.  Lake  Superior  copper  is  preferred  on  account 
of  its  toughness,  ^nd  German  tin  for  its  purity.  The  greatest 
care  is  necessary  to  keep  the  compound  free  from  sulphur,  lead, 
iron,  and  arsenic,  for  any  of  these  would  lessen  the  value  of 
the  alloy  for  the  required  purpose.  (Art.  135.) 

528.  In  consequence  of  the  different  fusibility  of  copper 
and  tin,  the  perfection  of  the  alloy  depends  much  upon  the 
treatment  of  the  melted  metal.  If  the  tin  be  not  quickly  uni- 
ted with  the  copper,  it  will  be  burned,  and  converted  into 
scoria ; but  such  are  the  affinities  of  the  metals,  that  the  loss 
which  might  be  expected  from  the  burning  of  the  tin  is  pre- 
vented by  its  being  retained  by  the  more  stable  copper.  It  is 
very  essential  that  the  metals  be  thoroughly  incorporated,  for 
the  tin,  being  the  lighter,  would  remain  on  the  surface,  and 
there  would  be  no  union  of  the  metals  whatever. 


172 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  copper  is  first  introduced  into  the  furnace  through  the 
side-door,  I),  in  the  form  of  ingots  of  about  eighteen  pounds 
Aveight : tAvo  tliousand  pounds  of  copper  being  required  in  cast- 
ing the  lieavy  twelve-pounder  howitzer  of  seven  hundred  and 
fiity  pounds  Aveight. 

523.  Melting  down  the  Chaege. — The  fuel  used  for  melt- 
ing is  spruce  pine,  three-fourths  of  a cord  being  required  for 
each  ton  of  copper ; Avood  is  used  in  preference  to  coal,  because 
the  gases  evolved  are  not  so  injurious  to  the  copper. 

The  furnace  being  closed,  the  fire  is  started ; from  three  to 
four  hours  are  required  to  fuse  the  copper,  depending  upon 
the  force  and  direction  of  the  wind  and  the  state  of  the  atmos- 
phere. 

530.  At  the  moment  at  which  fusion  takes  place,  the  tin, 
Avhich  is  prepared  in  the  form  of  ingots,  each  Aveighing  about 
seven  pounds,  is  throAvn  into  the  furnace  through  a door,  one 
at  a time ; care  being  taken  to  submerge  the  ingot  thus  intro- 
duced ill  order  that  it  may  not  spread  itself  on  the  surface  of 
the  copper  and  become  oxydized ; the  Avhole  mass  being  kept 
in  a state  of  agitation  bv  means  of  a rabble  introduced  through 
the  same  door. 

The  molten  mass  is  thus  puddled  until  the  metals  arc  thor- 
oughly incorporated,  Avhich  operation  requires  about  four  min- 
utes ; the  rabble  is  then  AvithdraAvn,  the  door  closed,  and  the 
damper  raised. 

531.  The  compound  is  uoav  subjected  to  an  intense  heat  for 
about  thirty  minutes,  or  until  the  founder  is  satisfied  that  the 
mass  has  been  reduced  to  the  required  state  of  liquefaction. 
It  is  almost  impossible  to  give  any  rule  as  to  Avhen  the  metal  is 
ready  for  running,  as  those  Avho  are  experienced  in  the  matter 
tell  by  its  color  and  general  appearance  ; Avhich  is  defined  as  a 
yellow-red  color. 

532.  When  the  pure  metals  are  not  used,  the  charge  is 
made  up  of  remnants  of  other  castings  and  shaAungs  from  the 
lathe,  etc.,  Avliich  are  re-melted  Avith  a sufficient  quantity  of 
zinc  and  tin  to  preserve  the  proper  proportions.  (Art.  138.) 

In  a light  12-pdr.,  cast  in  1871,  the  furnace  was  charged 
with : 


One  2I-pdr.,  Howitzer 1,280  lbs. 

Lake  Copper 75  “ 

A gun  muzzle 100  “ 

Ingots  (Bronze) 115  “ 


Total 1,600  “ 


CAST  GUNS. 


173 


In  a light  12-pdr.,  cast  in  1872,  the  furnace  was  charged 


with : 

Two  Heads 1,420  lbs. 

Ingots  (Bronze) 205  “ 

Tin 2 “ 

Zinc 2 ‘‘ 


Total 1,G29  “ 

In  a heavy  12-pdr.,  cast  in  1865,  the  furnace  was  charged 
with : 

Lake  Copper 800  lbs. 

Ingots  (Bronze) 1,000  “ 

One  Head GOO  “ 


Total 2,400  “ 


533.  Casting. — In  casting  it  is  customaiy  to  allow  the 
melted  metal  to  run  first  through  the  side-runner  until  it  rises 
two  or  three  inches  above  the  loop  ; the  stream  is  then  trans- 
ferred directly  through  the  top  of  the  mold  and  allowed  to  run 
in  until  the  mold  is  filled.  This  is  done  to  prevent  the  upper 
part  of  the  casting  from  cooling  too  rapidly,  and  thereby  ctius- 
mg  an  unequal  distribution  of  the  tin,  this  metal  being  found 
always  in  the  greatest  quantities  in  that  part  of  the  casting 
which  retains  heat  the  longest.  (Art.  137.)  It  is  considered 
impossible  to  render  the  alloy  perfectly  homogeneous,  because 
of  the  difference  of  fusibility  and  specific  gravity  of  the  con- 
stituent metals.  (Art.  140.) 

534.  To  ti’ansfer  the  stream  of  melted  metal,  a simple  device 
is  resorted  to.  It  consists  of  two  rionner-hoxes  of  cast-iron.  A,  B 
(Fig  7G).  The  lower  one  has  a partition  dividing  it  into  two 
chambers,  with  an  orifice  in  the  bottom  of  each,  so  fitted  that 
Avhen  it  is  placed  on  the  flask,  F,  one  orifice  Vvdll  lead  fair  into 
the  runner,  and  the  other  directly  into  the  mold. 

535.  The  upper  runner-box  slides  on  the  upper  edge  of  the 
lower  one,  and  is  furnished  with  handles  to  facilitate  the  opera- 
tion. Its  bottom  is  pierced  with  a single  orifice  to  allow  the 
stream  of  metal  to  flow  successively  into  the  inner  and  outer 
chambers  of  the  lower  one. 

The  upper  runner-box  is  also  fitted  with  a spout,  which, 
when  they  are  in  position,  comes  directly  under  the  spout,  S, 
at  the  gate  of  the  furnace  ; it  is  long  enough  to  allow  for  the 
distance  between  the  first  and  second  positions  of  the  upper 
runner-box. 


174: 


NAVAL  ORDNANCE  AND  GUNNERY. 


536.  Tlie  spouts  and  runner-boxes,  well  lined  with  clay,  be- 
ing secured  in  position,  and  tbe  furnace  ready  to  tap,  an 
orifice  is  made  in  its  gate  and  tbe  metal  allowed  to  run  in  tbe 
mold.  From  the  gate  it  is  conducted  by  the  spoilt  into  the 
upper  runner-box ; flowing  from  thence  through  the  orifice,  it 
passes  into  the  inner  chamber  of  the  lower  runner-box,  and 
down  through  the  side-runner  and  its  branch  into  the  bottom 
of  the  mold. 

537.  At  the  moment  the  founder,  who  is  looking  down  into 
the  mold,  discovers  that  the  metal  has  arisen  above  the  loop, 
he  causes  the  upper  runner-box  to  be  shifted,  so  that  the  stream 
is  transferred  to  the  outer  chamber  of  the  lower  runner-box. 
When  the  mold  is  filled  the  gate  is  plugged  up,  the  runner- 
boxes  are  removed,  and  the  casting  allowed  to  cool.  When  the 
casting  has  become  sufficiently  solid  to  be  removed,  the  mold  is 
hoisted  out.  The  remaining  metal  in  the  furnace  is  drawn  ofl; 
in  ladles,  and  cast  into  rough  ingots  for  future  use. 

The  casting  having  become  sufficiently  cool  to  be  handled, 
the  flask  is  opened,  the  gun  taken  out,  and  with  a hammer  and 
chisel  the  sand  and  rough  projections  removed.  The  gun  is  then 
ready  for  the  lathe. 


Section  IV. — Inspection. 

538.  Inspection  of  New  Guns.— New  guns  are  to  be  closely 
examined  and  measured  inside  and  out,  for  defects  of  metal  or 
manufacture,  as  soon  after  being  finished  as  possible,  if  it  has 
not  already  been  done  in  the  various  stages  of  manufacture. 

For  this  purpose  the  gun  is  placed  on  skids,  so  that  it  may 
be  easily  moved,  and  its  foundry  number  is  noted  so  as  to 
identify  the  jiiece. 

As  rust  tends  to  conceal  defects,  this  examination  is  to  take 
place  before  exposure  to  the  weather ; and  previously  to  the 
final  examination  and  proof  of  the  guns,  they  are  not  to  be 
covered  with  paint,  lacquer,  oil,  or  any  material  which  may 
conceal  defects  of  metal. 

539.  If  it  is  ascertained  that  any  attempt  has  been  made  to 
conceal  defects,  the  gnus  so  treated  are  to  be  rejected  without 
further  examination. 

The  water-proof,  which  is  of  great  importance  in  detecting 
defects  of  metal,  not  otherwise  developed,  necessarily  succeeds 
immediately  the  powder-proof,  and  can  only  be  effectively  em- 
ployed in  fine  weather,  and  when  the  temperature  is  above 
the  freezing-point;  final  inspections  are  to  be  made  at  such 
times  only. 


INSPECTION  OF  GUNS. 


175 


540.  THE  IHSPECTIHG-IHSTRUMENTS.— The  in- 
specting-instruments  are  first  carefully  verified  before  any 
measurements  are  taken.  Tliey  may  be  described  and  their 
uses  explained  as  follows : 

541.  A Mieeoe,  for  reflecting  the  sun’s  raj^s. 

TJse. — The  interior  of  the  bore  fs  to  be  examined  by  reflect- 
ing the  rays  of  the  sun  into  it  from  the  mirror  or  mirrors  ; or, 
if  the  sun  is  obscured,  and  there  can  be  no  delay,  by  means  of 
a spirit-lamp  or  of  a wax-taper  on  the  end  of  a rod,  taking  care 
not  to  smoke  the  sui’face  of  the  bore. 

542.  The  Seaechee  consists  of  a long  staff  of  wood,  fitted 
with  a head  of  six 

or  seven  steel  points 
(Fig.  77).  The  points 
are  arranged  at  equal 
intervals  around  the 
head,  and  attached 
with  a tendency  to 
spring  out  and  increase 
their  diameter ; this  ten- 
dency is  restrained  by 
a hoop  of  iron  embrac- 
ing them,  and  capable 
of  being  worked  in  and 
along  the  staff. 

543.  TJse. — The  searcher  is  used  for  detecting  the  presence 
of  small  cracks  or  flaws.  To  use  the  instrument  the  hoop  is 
pushed  out  on  the  head,  thus  contracting  the  points;  it  is  then 
introduced  in  the  gun  to  the  bottom  of  the  bore,  and  the  hoop 
being  pidled  back  allows  the  points  to  spring  out  and  take 
against  the  surface  of  the  bore.  The  searcher  is  then  slowly  with- 
drawn, turning  it  at  the  same  time  ; if  one  of  the  points  catches, 
its  distance  from  the  muzzle  is  measured  on  the  staff,  and  its 
position  in  the  bore  noted,  and  marked  on  the  exterior  of  the 
gun.  The  size  and  figure  of  the  cavity  is  then  determined  by 
taking  an  impression  of  it  in  wax. 

544.  The  Cyltndee-gauge. — This 
is  a hollow  cylinder  of  iron,  turned 
to  the  least  allowed  diameter  of  the 
bore,  and  one  calibre  in  length  (Fig. 

78).  It  has  a cross-head  at  each 
end,  one  of  which  has  a smooth  hole 
through  its  axis  to  fit  the  staff,  and  the 
other  is  tapped  to  receive  the  screw 

in  the  end  of  it.  Fig.  78. — Cylinder-gauge. 


176 


NAVAL  ORDNANCE  AND  GUNNERY. 


545.  Use. — The  cylinder-gauge  is  introduced  in  the  hore  of 
the  gnn,  and  must  pass  freely  to  the  bottom  of  the  hore. 

This  instrument  shows  that  the  bore  is  not  too  small. 

546.  A Measuking-staff. — This  is  a stalf  of  steel  or  iron 
(Fig.  79),  in  joints  of  suitable  lengths,  connected  togetlier  by 
screws.  Each  joint  is  provided  with  a light  brass  disk,  DD,  the 
diameter  of  which  is  0.05  inches  less  than  that  of  the  bore. 


Through  the  centre  of  the  disk  there  is  a hole  which  fits  upon 
the  shoulder  at  the  joint ; the  whole  is  so  arranged  that  udien 
the  joints  are  screwed  together  the  disks  between  them  ai’e  held 
firmly  in  place,  while  tlie  length  of  the  staff  is  not  affected  by 
them.  A steel  point,  P,  is  screwed  on  to  the  end.  When 
pushed  to  the  bottom  of  the  bore,  the  staff  coincides  very  nearly 
with  its  axis.  The  outer  joint  is  graduated  to  inches  and  tenths. 

A slide,  S,  is  made  to  play  upon  it  with  a vernier  scale, 
graduated  to  hundredths  of  an  inch.  On  the  inner  end  of 
the  slide,  a branch,  B,  projects  at  a right  angle,  sufficiently  long 
to  reach  across  the  muzzle-face,  and,  when  in  contact  with  it,  to 
indicate  the  precise  length  obtained  from  that  point  to  the  end 
of  the  measuring-point  on  the  other  end  of  the  staff. 

547.  Use. — The  instrument  is  introduced  until  the  point 
reaches  the  bottom  of  the  boi-e,  and  the  branch  placed  so  that  it 
takes  across  the  muzzle-face,  and  the  reading  shows  the  length 
of  the  bore  of  the  gun. 

548.  CiiAjiBEK-GAUGE. — The  head  should  be  made  of  close- 
grained,  well-seasoned  wood,  and  of  the  exact  dimensions  of 
the  chambe]’. 

Two  planes  crossing  each  other  at  a right  angle,  coinciding 
with  the  vertical  and  horizontal  central  sections,  have  been 
found  better  than  a solid  block.  The  edge  should  be  bevelled. 
A socket  in  its  centre  connects  it  with  the  measuring-stiiff. 

549.  Use. — Being  pushed  to  the  bottom  of  the  bore,  if  the 
length  coincides  with  that  obtained  by  the  point,  it  is  obvious 
that  the  chamber  is  large  enough,  provided  the  cylindrical  pare 
has  not  been  bored  too  deep,  in  which  case  a shoulder  would  be 
found  at  the  junction. 


I 


INSPECTION  OF  GUNS.  177 

The  edges  of  the  gauge  should  he  chalked  before  inserted. 
When  withdrawn,  if  the  chalk-marks  are  visible  all  around  the 
chamber,  it  is  evident  the  chamber  is  not  too  large. 

An  e.xamination  of  the  chamber-reamer  (Art.  503)  will  be 
very  satisfactory,  and  if  found  correct  in  size  and  shape,  the 
impossibility  of  making  the  chamber  too  large  will  be  apparent. 

550.  Stak-gauge. — This  instrument  is  composed  of  the 
staff,  the  head,  and  the  handle  (Fig.  80). 


Fig.  80. — Star-gauge. 

The  staff  is  a brass  tube,  S,  made  in  three  pieces,  for  con- 
venience of  storage,  and  connected,  when  required,  by  screws. 
It  is  graduated  to  inches  and  cj^uarters,  so  that  the  distance  of 
the  head  from  the  muzzle  of  the  gun  may  always  be  known. 

A centre-line,  starting  from  the  centre  of  the  upper  socket 
in  the  head,  is  marked  upon  the  statf  throughout  its  length. 

551.  The  Head. — The  inner  end  of  the  staff  expands  into 
a head,  H (Figs.  81  and  82),  in  which  are  placed  four  steel 


Fig  81. — Head  of  Star-gauge. 

sockets,  K,  at  equal  distances  from  each  other ; two  of  the  sock- 
13 


178 


NAVAL  OKDNANCE  AND  GUNNERY. 


ets  opposite  to  eacli  other  are  secured  permanently,  and  the 
other  two  are  movable. 

552.  A wedge,  or  tapering  plate,  "W,  the  sides  of  which  are 
cylindrical,  runs  through  a slit  in  the  head  (Fig.  82) ; an  aper- 


Fig.  83. 


tnre  in  the  inner  end  of  the  movable  sockets,  AA,  embraces  the 
cylinders,  so  that  when  the  wedge  is  moved  forward  or  back- 
ward, the  sockets  are  projected  or  withdrawn. 

The  tapering  of  the  wedge  has  a certain  known  proportion 
to  its  length,  so  that  if  it  is  moved  in  either  direction  a given 
distance,  a proportional  movement  is  imparted  to  the  sockets. 
The  sides  of  the  wedge  incline  0.35  inch  in  a length  of  2.2 
inches,  so  that  by  pushing  it  the  thirty-fifth  part  of  this  dis- 
tance (about  0.06  inch),  the  distance  between  the  two  sockets 
is  increased  .01  inch. 

553.  There  are  four  steel  measuring-points,  P,  for  each  cal- 
ibre, fitted  with  strong  shoulders  at  one  end,  below  which 
threads  are  cut  for  screwing  into  the  sockets  in  the  head.  A 
wrench  is  made  to  fit  the  shoulders,  so  as  to  turn  the  points 


INSPECTION  OF  GUNS, 


179 


firmly  into  tlieir  places  ; when  two  of  these  are  screwed  into  the 
fixed  sockets,  the  distance  between  their  extremities  is  equal  to 
the  true  diameter  of  the  bore. 

551.  A square  steel  sliding-rod,  R,  is  connected  with  the 
wedge  in  the  head,  and  runs  through  the  whole  length  of  the 
staff,  projecting  some  inches  beyond  the  outer  end.  This  rod 
has  as  many  parts  as  there  are  joints  in  the  staff  (three),  and, 
like  them,  connects  by  screws. 

555.  The  Handle  (Fig.  83)  is  attached  to  the  projecting 
end  of  the  sliding-rod.  It  is  a short  hollow  tube  of  brass,  MB, 
made  to  fit  over  the  outer  end  of  the  staff,  S,  and  connect  with 
the  sliding-rod,  R,  by  a screw  at  its  outer  extremity  fitted  with 
a large  milled-head,  M.  The  handle  is  divided  into  two  parts, 


one  fitting  and  working  closely  over  the  other.  On  each  side 
of  the  inner  part  is  a small  tube,  CD  ; a thread  is  cut  in  one,  D, 
through  which  a fine  screw,  held  by  a stud  on  the  outei’  part,  E, 
works  and  gives  it  motion  ; a guide,  F,  runs  through  the  other. 
A slit,  Gr,  through  the  inuer  part  of  the  handle  permits  a part 
of  the  staff  near  the  end  to  be  seen  beneath,  and  a scale  is 
placed  on  one  side  of  the  slit  graduated  with  the  distance  that 
the  wedge  moves  to  throw  the  points  .01  inch  apart. 

556.  Adjusting  the  Instrument. — There  is  a steel  adjusting- 
ring  (Fig.  84)  for  each  calibre,  reamed 
out  to  the  exact  minimum  diameter  of 
the  bore.  The  fixed  measuring-points  of 
the  head  will  just  pass  into  the  adjusting- 
ring of  the  corresponding  calibre ; the 
movable  points  are  made  to  touch  the  in- 
ner circumference  of  the  ring  by  pressing 
in  the  wedge;  and  this  is  accomplished  by 
moving  in  the  handle.,  which  works  the 
sliding-rod.  Seen  through  the  slit  of  the 
handle,  G,  is  a small  plate  of  silver,  I,  in- 
serted in  the  staff,  and  a fine  mark  upon 
it  to  show  the  place  of  zero  when  the  measuring-points  are 
adjusted. 


180 


KAVAL  ORDA^ANCE  AAD  GUA'XEET. 


The  zero-mark  on  the  scale  along  the  slit  is  made  to  cori'e- 
spond  with  it  by  means  of  the  line  screw,  ED. 

557.  A Muzzle-rest  in  the  form  of  T is  employed  to  keep 
the  staff  of  the  star-gange  in  the  axis  of  the  Lore  while  it  is  be- 
ing used  (Fig.  85).  It  contains  a groove,  A,  in  the  centre  of  the 

transverse  branch,  to 
receive  the  lower  half 
of  the  staff,  and  can  be 
used  with  any  c<alibre, 
as  there  is  a movable 
slide  on  each  branch, 
S,  which  can  be  ad- 
justed to  marks  for  the 
calibre,  so  that  points 
projecting  from  the 
rear  will  enter  the 
muzzle  and  hold  the 
rest  in  place.  In  this 
position  the  upper  edge  of  the  transverse  branch  coincides  with 
the  diameter  of  the  boi’e.  A hook  is  secm’ed  on  the  inner  side 
of  the  transverse  branch,  on  one  side  of  the  groove,  and  so  fitted 
that  when  the  star-gauge  is  in  the  gun,  it  embraces  one-half  of 
that  portion  of  the  staff  which  is  above  the  groove.  Therefore, 
if  the  transverse  branch  be  placed  so  as  to  coincide  with  the  axis 
of  the  trunnions,  the  hook  thrown  over  the  staff,  and  the  latter 
turned  so  that  the  centre-line  just  meets  the  end  of  the  hook, 
two  of  the  measuring-points  will  be  in  a plane  perpendicular  to 
the  axis  of  the  trunnions  (Art.  550).  If  the  staff  is  then  drawn 
out  carefully,  without  turning,  measurements  may  be  taken  in 
the  same  plane.  A notch  in  the  end  of  the  hook,  made  to  coui- 
cide  with  the  face  of  the  muzzle,  will  mark  the  distances  on  the 
staff. 

558.  A dish  for  circular  measurements  is  employed  when  it 
is  desired  to  take  the  diameter  of  the  bore  at  many  points  of  the 
circle.  There  is  a brass  tompion,  V,  to  tit  the  muzzle  of  the  gun, 
with  a hole  through  its  centre  to  receive  the  staff  of  the  star- 
gauge  (Fig.  86). 

It  is  turned  to  fit  snugly  the  bore  of  the  piece,  into  which  it 
enters  two  or  three  inches,  to  hold  it  firmly  in  place ; and  has  a 
projecting  flange  or  face  to  jarevent  it  going  in  too  far.  The 
face  is  a plane  surface  with  its  circumference  divided  into  as 
many  equal  parts  as  may  be  thought  desirable,  and  numbered  in 
regular  order. 

559.  On  the  staff  of  the  star-gauge  a brass  slide,  X,  is  fitted, 
having  a thumb-screw  to  hold  it  in  any  position  ; from  its  inner 


I^"SPECTIOX  OF  GUI^S. 


181 


end  an  arm,  Z,  extends  at  right  angles  to  the  staff,  of  sufficient 

length  to  meet  the 
points  on  the  circum- 
ference of  the  disk  and 
having  a centi-e  line 
marked  upon  it.  This 
slide  is  secured  at  any 
distance  on  the  staff  at 
which  a chcnlar  meas- 
nrement  is  desired, 
and  with  the  centre- 
line of  the  arm  coin- 
ciding with  the  centre- 
line of  the  staff ; when 
the  arm  will  indicate 
the  direction  of  the 
pair  of  measnring- 
points ; being  in  the 
same  plane  with 
them. 

560.  The  disk  is  secured  in  the  muzzle,  with  its  zero-mark 
coinciding  with  a light  punch-mark  on  the  muzzle-face  directly 
helow  the  line  of  sight,  so  that  it  is  in  a j^lane  passing  throngli 
the  axis  of  the  piece  and  perpendicular  to  the  axis  of  the  trun- 
nions. To  take  the  measurements,  press  the  staff  home  imtil  the 
arm  of  the  slide  comes  in  contact  with  the  face  of  the  disk,  and 
turn  it  to  coincide  with  the  various  divisions  of  the  disk  at  which 
measurements  are  desired. 

661.  The  disk  is  divided  into  halves,  and  tlie  centre-hole  is 
reinforced  on  the  inside  by  a projection,  which  is  turned  to 
receive  a collar  that  fits  closely  around  it,  and  holds  the  two 
halves  together  when  they  are  placed  on  the  staff. 

562.  Use. — The  star-gauge  is  used  to  obtain  the  exact  diame- 
ter of  the  bore.  Tt  is  obvious  that  the  determinations  will  not 
be  absolutely  accurate,  for  when  the  gun  is  worn,  should  the 
stationary  points  be  perpendicular,  the  movable  points,  being 
then  horizontal,  would  fall  below  the  true  horizontal  diameter, 
and  measurements  would  be  more  in  error  than  it  would  be 
with  the  points  in  any  other  direction.  Still  if  care  is  taken  to 
preserve  the  points  at  the  greatest  length  possible,  a very  toler- 
able degree  of  accuracy  may  be  attained. 

563.  In  the  inspection  of  guns  arranged  on  skids,  the  gun 
itself  should  be  turned,  which  will  insure  accurate  measure- 
ments. Care  must  also  be  taken  not  to  allow  the  joints  of  the 
staff  to  become  so  loose  that  the  coincidence  of  the  centre-line 


Fig.  86. 


182 


NAVAL  ORDNANCE  AND  GUNNERY, 


is  destroyed  wlien  they  are  screwed  together.  If  this  should 
occur,  however,  a few  turns  of  thread,  placed  between  them  at 
the  time  of  putting  the  instrument  together,  would  remedy  the 
difficulty. 

561.  The  bore  must  he  measured  at  intervals  of  one-quarter 
inch  from  the  bottom  of  the  cylindrical  part  to  the  seat  of  the 
projectile;  of  one  inch  from  that  point  to  the  trunnions;  and^ 
of  live  inches  from  the  trunnions  to  the  muzzle.  If  any  marks 
of  the  reamer^  or  other  defects  are  seen  in  the  bore,  they  are  to 
be  searched  for,  and  their  depths  and  positions  noted. 

These  results  are  to  be  tabulated  according  to  the  blank 
forms  furnished  by  the  Bureau  of  Ordnance. 

565.  In  recording  the  measurements  of  the  bore  in  extreme 
proof  and  after  service,  it  is  necessary  to  distinguish  between 
“ indentation,”  that  is,  the  depression  at  the  “ seat  of  the  shot,” 
which  is  always  below,  the  “ wear  of  the  bore,”  which  is  gener- 
ally above,  and  the  increase  of  bore,  or  “ enlargement  ” from 
any  other  cause  (Art.  608.) 

566.  A Vekt-guide,  to  be  used  with  vents  in  guns  of  the 
Dahlgren  pattern  (Fig-  87). 

This  instrument  is  made  of  bronze  or  composition.  When 
placed  upon  tlie  gun,  one  of  its  branches  coincides  with  the 

curve  of  the  cylinder,  and  the 
other,  starting  from  its  centre,  lies 
along  the  cylinder  in  contact  with 
it  longitudinally.  The  lower  edges 
of  the  branches  are  a right  line  and 
a curved  line,  making  two  right 
angles  with  each  other.  The  length 
of  that  of  the  transverse  branch  is 
equal  to  the  distance  between  the 
centre  of  the  two  vents.  The  rear 
surface  of  the  transverse  branch  is  curved  and  quadrilateral.  Its 
sides  are  inclined  so  that  their  rear  edges,  YV,  show  the  exact 
direction  of  the  vents.  Every  point  in  the  upper  edge  lies  in 
the  same  horizontal  plane.  The  height  is  sufficient  to  permit  the 
edges  to  give  an  accurate  direction  to  the  drill.  The  upper  edge 
of  the  other  branch  runs  off  in  a sloping  curve  to  its  extremity. 

A centre-line  is  drawn  through  the  lower  edge  of  the  longi- 
tudinal branch,  and  is  continued  upwards  on  the  rear  smffaceof 
the  transverse  branch  to  the  top. 

567.  Use. — The  guide  being  placed  with  its  centre  upon  the 
centre-mark  of  the  gun,  and  the  centre-line  of  the  longitudinal 
branch  being  made  to  coincide  with  the  centre  scribed  upon  the 
cylinder,  the  rear  lower  end  of  the  transverse  branch  will  tlieu 


Fig.  87. — Vent-guide. 


msPECTioisr  of  ouisrs. 


183 


coincide  with  the  base-line,  its  extremities  will  indicate  the  cen- 
tres of  the  vents,  and  the  rear  edges  of  the  sides  will  show  their 
true  direction. 

568.  An  instrument  for  verifying  the  interior  position  of 
vents.  , 

A head  of  well-seasoned  wood,  which  fits  the  chamber,  is‘ 
attached  to  a wooden  disk  of  the  diameter  of  the  main  bore. 
The  surface  of  the  head  corresponds  with  a longitudinal  central 
section  of  the  chamber ; at  the  point  where  the  projection  of  the 
vent  would  meet  it  a piece  of  hard  wood  is  inserted.  A central 
line  drawn  through  its  length,  crossed  at  a right-angle  by  an- 
other line  at  any  known  point  from  the  smaller  end,  will  afford 
convenient  points  to  measure  from. 

A stout  wooden  staff  is  attached  to  the  axis  of  the  head ; at 
a distance  equal  to  the  length  of  the  bore,  the  end  is  jogged 
into  the  centre  of  a half -disk  of  wood,  which  is  fitted  to  the  bore. 

The  whole  is  so  constructed  that  the  straight  edge  of  the 
half-disk  (or  the  cord)  is  in  the  same  plane  as  a horizontal  sec- 
tion of  the  head.  A few  holes  are  bored  through  the  disk 
attached  to  the  half-head,  to  allow  the  instrument  to  pass  freely 
into  the  gun  and  out  of  it. 

669.  A wire  of  untempered  steel,  of  the  size  of  the  vent, 
with  a sharp,  well-centred  point,  and  a small  spirit-level.,  are 
required  to  use  with  this  instrument. 

570.  Use. — The  gun  being  levelled,  and  the  instrument  being 
pushed  to  the  bottom  of  the  bore,  the  upper  edge  of  the  half- 
disk near  the  outer  end  of  the  staff  is  then  brought  to  a level. 

The  siirface  of  the  half-head  then  corre- 
sponds with  the  horizontal  central  section  of 
the  chamber.  The  point  of  the  wire  being 
pushed  gently  to  meet  it,  will  show  very 
accurately  the  interior  position  of  the  vent. 

571.  Vent-gauges  of  untempered  steel- 
wire,  with  shoulders  to  prevent  them  from 
slipping  into  the  vent  (Fig.  88).  One 
should  be  of  the  proper  diameter  of  the 
vent,  one  of  the  greatest,  and  one  of  the 
least,  diameter  allowed. 

572.  Use. — The  diameter  of  the  vent  is 
measmed  by  the  gauges,  the  smallest  of 
which  must  enter  freely,  and  the  largest 
not  at  all. 

573.  A Yent-seaecher,  a steel  wire  of  the 
vent,  bent  to  a right  angle  at  the  lower  end  and  poiiited. 

Use. — The  vent  is  examined  for  roughness  or  for  cavities  in 


i 


Fig.  88. — Vent-gauges. 


length  of  the 


18i 


NAVAL  ORDNANCE  AND  GUNNERY. 


tlie  metal  by  means  of  the  searcher,  the  point  of  which  should 
feel  every  portion  of  it  carefully. 

57d.  A Semicieculae  Peoteactoe  of  metal  for  measuring 
the  inclination  of  vents,  or  for  ascertaining  their  deviation  from 
the  guide. 

575.  Peofile-boaeds,  for  distances  in  front  and  rear  of  base- 
line. 

Their  lower  edges  are  adapted  to  the  shape  of  the  gun,  and 
the  upper  ones  are  parallel  to  the  axis  of  the  bore. 

The  distances  from  the  base-line  of  the  several  parts,  and  of 
points  at  which  diameters  are  to  be  measured  (Fig.  24),  are  laid 
otf  aecui’ately  on  the  upper  edge,  and  then  marked  in  lines  per- 
pendicular to  it  on  the  sides  and  lower  edges  of  the  profile.  An 
iron  strap  is  attached  to  the  upper  edge  to  prevent  warping,  and 
the  whole  is  well  coated  with  shellac-varnish  to  keep  it  from 
absorbing  moisture. 

57G.  The  following  instruments  are  used  in  connection  with 
the  profile-boards  : 

A ride,  for  verifying  the  marks,  of  such  a length  that  not 
more  than  one  fleeting  may  be  necessary,  to  be  graduated  deci- 
mally according  to  the  standard. 

A small  square  of  steel,  to  be  used  in  referring  the  marks 
on  the  board  to  those  on  the  rule. 

A steel  straight-edge,  long  enough  to  extend  across  the  muz- 
zle-face and  several  inches  on  the  board,  to  ascertain  the  ex- 
treme length  from  base  to  muzzle.  It  is  also  used  for  the  same 
purpose  at  the  extreme  end  of  the  cascabel. 

A steel  scr atelier,  to  mark  the  gun  at  points,  not  otherwise 
indicated,  where  diameters  are  to  be  measured. 


577.  A Be.ui-calipek,  for  measuring  diameters,  is  a square 


185 


I 

INSPECTION  OF  GUNS. 


of  steel  or  iron  (Fig.  89),  with  two  branches,  one  of  which  is 
fixed  and  the  other  sliding. 

The  inner  edges  of  the  two  branches,  when  pushed  together, 
lie,  of  course,  in  contact  with  each  other  throughout  their  length. 
The  beam  is  graduated  to  inches  and  tenths.  A vernier  is  at- 
tached to  the  slidino;-branch,  graduated  to  hundredths  of  an  inch. 


The  latter  is  provided  with 
any  point. 


a thumb-screw  to  fasten  it  at 


The  lengtii  of  the  beam  must  he  rather 


greater  than  the 


diameter  ; and  that  of  the  branches  than  the  semi-diameter  of 
the  gims  to  be  inspected,  at  their  largest  points. 

578.  A Cascabel-block  is  a wooden  cylinder  of  the  proper 
, diameter  of  the  breeching-hole,  the  size  of  which  it  is  used  tb 

verify. 

The  opening  between  the  jaws  may  he  ascertained  by 
measuring  the  iron  block  wiiich  is  fitted  to  go  between  them,  or 
by  a template. 

579.  A Tbuxnion-gatjge  is  an  iron  ring  of  the  proper  diam- 
eter of  the  trunnions  (Fig.  90).  Its  outer  edge  coincides  with 
the  diameter  of  the  rim-bases. 

Use. — To  verify  the  position  and  alignments  of  the  trun- 
nions of  a gun,  it  is  first  necessary  to  ascertain,  by  means  of  the 
trunnion -gauge  and  of  the  calipers,  their 
cylindrical  form  and  their  diameters, 
which  should  be  the  same,  or  allowance 
must  be  made  for  half  the  difference  in 
measuring  their  axial  distances  from  the 
base-line,  by  the  Uunnion-rule,  wdiich 
should  next  be  done.  These  distances 
should  be  equal,  or  their  axes  do  not  co- 
incide, an  error  not  tolerated. 

The  lengths  of  the  trunnions  are 
measured  with  the  foot-ride,  and  the 


Fig.  90. — Trunnion-g'auge. 


diameters  of  the  rim-bases  by  that  of  the  exterior  rim  of  the 
trunnion-gauge. 

580.  A TkunniojST-squaee  (Fig.  91)  of  steel  or  iron  for  ascer- 
taining the  position  of  the  trunnions,  with  reference  to  the  axis 
of  the  bore.  This  instrument  is  a square,  with  twm  branches, 
one  of  which  is  fixed,  and  the  other  movable. 

The  foot  of  each  branch,  TT,  is  in  the  same  plane,  and  is 
parallel  to  the  upper  edge  of  the  main  piece  ivhieh  connects 
them.  The  latter  is  graduated  to  inches  and  tenths.  The  mov- 
able branch,  B,  slides  on  the  main  piece,  and  may  be  secured  to 
it  by  two  thumb-screws,  S.  It  is  provided  with  a vernier-scale 
graduated  to  hundredths  of  an  inch. 


186 


NAVAL  ORDNANCE  AND  GUNNERY. 


Between  the  branches  there  is  a slide,  B,  also  provided  with 
a vernier,  graduated  as  before,  with  a thumb-screw  to  secure  it 
firmly  ; in  its  centre  there  is  a sliding  point,  P,  moving  verti- 
callyj  with  a tlmmh-screw  to  fasten  it.  Above  the  foot  of  each 
branch  there  is  a slit  to  receive  the  shank  of  a plate,  H,  on  the 
end  of  which  a thread  is  cut ; the  lower  edge  of  the  plate  forms 
a right  angle  with  the  branch,  and  the  plate  is  fastened  to  the 
branch  by  a nut,  at  a point  from  the  end  equal  to  the  semi- 
diameter of  the  trunnion  which  is  marked  on  each  branch. 

A graduated  steel  Avedge,  W,  is  used  to  measure  the  devia- 
tion of  the  trannions  from  the  feet  of  the  square. 

581.  Use. — ^When  the  feet  of  the  branches,  or  the  lower 
edce  of  the  plates,  rest  upon  the  trunnions,  the  upper  edge  of 


the  main  y)iece  is  parallel  to  their  axis,  if  their  alignement  is 
correct.  When  in  the  latter  position,  the  edges  of  the  feet  Avill 
lie  close  agamst  the  sides  of  the  trunnions. 

The  trunnion-square  is  placed  upon  the  trunnions  in  the 
plane  of  their  axis.  The  feet  of  its  branches  should  coincide 
with  the  surfaces  of  both  trunnions,  throughout  their  length, 
above  and  in  rear,  and  then'  inner  edges  with  the  faces  of  the 
rim-bases. 

582.  Then,  Avith  the  heam-com/pass  (Fig.  92),  scribe  on  the 


Fig.  93. — Beam-compasses. 


upper  surface  of  the  gun  the  distance  of  the  axis  of  the  trun- 


INSPECTION  OF  GUNS. 


18T 


nions  from  the  base-line,  and  pnsli  the  sliding-point  of  the  square 
down,  till  at  that  distance  it  touches  the  surface  of  the  gun,  and 
screw  it  fast. 

Turn  the  gun  over,  and  again  scribe  on  it  the  same  distance 
from  the  base-line.  The  square,  being  again  applied,  will  deter- 
mine whether  the  trunnions  are  above  or  below  the  axis  of  the 
bore,  which  will  coincide  with  that  of  the  gun,  if  accurately 
bored,  and  turned  on  the  same  centres  and  bearings.  If  the 
branches  rest  upon  the  trunnions  before  the  point  of  the  slider 
touches  the  gun  at  the  scribe,  their  axis  is  below,  but  if  the 
point  touch  first,  above  the  axis  of  the  bore  by  half  the  space 
between.  The  graduated  wedge,  being  placed  under  the  verti- 
cal sliding-point,  wnll  determine  the  amount.  If  both  touch  at 
once,  both  axes  are  in  the  same  plane. 

ISTo  gun  can  be  received,  the  axis  of  the  trunnions  of  which  is 
above  the  axis  of  the  bore. 

583.  A Tkunnion-kule  (Fig.  93). — To  measure  the  distance 
of  the  trunnions  from  the  base-ring  or  hne.  This  is  an  iron  rod 


with  a head  at  one  end,  through  which  passes  one  branch  of  a 
small  square,  A.  The  centre  of  the  rod  is  marked  on  the  end, 
and  the  square  is  set  so  that  the  inner  edge  of  the  branch  which 
is  parallel  to  the  rod  is  at  a distance  equal  to  the  semi-diameter 
of  the  trunnion  from  the  centre.  It  is  secured  in  this  position 
by  screws  and  clamps. 

The  upper  side  of  the  rod  is  graduated  to  inches  and  tenths. 
A slide,  B,  with  a slot  through  it,  to  show  the  graduation  be- 
neath, traverses  upon  it,  and  is  kept  from  turning  by  a guide  on 
the  lower  slide.  There  is  a vernier  on  the  slide,  graduated  to 
hundredths  of  an  inch ; a thumb-screw  serves  to  secure  the  slide 
at  any  point  on  the  rod.  That  end  of  the  slide  from  which  the 
graduation  of  the  rod  commences  has  both  of  its  sides  drawn 
out,  to  form  knife-edges ; the  knife-edges  and  the  end  of  the 
slide  are  in  the  same  plane. 

584.  Use. — When  the  square  at  the  end  is  placed  on  the 
trunnions,  the  end  of  the  rod  will  touch  its  side  at  the  point  of 
its  greatest  diameter.  The  rod  being  held  parallel  to  the  axis 
of  the  bore,  with  the  side  of  the  head  pressing  the  rim-base,  the 


188 


NAVAL  ORDNANCE  AND  GUNNERY. 


knife-edge  will  be  in  a proper  positioii  to  fall  into  tlie  base-line 
wbeu  moved  to  find  it. 

585.  Line  of  Sight. — If  tire  alignement  of  tire  trunnions  be 
correct,  it  will  serve  as  a means  of  determinating  the  correctness 
of  the  line  of  sight.,  which,  before  the  gnn  is  removed  from  the 
lathe,  shonlcl  be  distinctly  traced  on  the  sight-masses  and  the 
swell  of  the  muzzle,  and  should  be  at  right  angles  to  the  base- 
line, to  the  axis  of  the  trunnions,  and  to  the  connecting-piece  of 
the  trunnion-square,  when  its  branches  rest  against  their  rear, 
with  the  plates  across  their  upper  surfaces. 

The  Inspector  will  further  satisfy  himself  of  the  correct  tracing 
of  the  line  of  sight  on  the  gun,  by  examining  the  lathe  and  the 
manner  of  tracing  it  in  the  plane  of  the  axis  of  the  bore,  at  right 
angles  to  the  axis  of  the  trunnions,  as  by  it  are  placed  the  sights 
and  vent,  and  in  their  absence  it  serves  as  a line  of  metal  sight. 

58G.  A Set  of  Templates  (big.  91),  for  verifying  the  shape 
of  Ipck-higs,  the  angle  of  the  rear  sight-mass,  the  curve  between 


the  rnuzzl e-swell. 

If  the  inspection  should  take  place  at  the  foundiy,  the  tem- 
plates used  for  chipping  might  be  verihed  and  used  for  inspection. 

For  guns  of  liahlgren’s  pattern,  a bronze  model,  showing 
the  shape  of  the  lugs  and  rear  sight-mass,  and  the  position  of 
the  vents,  is  furnished  as  a guide  to  the  contractors. 

587.  A standard  foot-rule  for  verifying  measures. 

A foot-rule  of  steel  for  measuring  the  masses,  the  length  of 
the  trunnions,  and  for  other  purposes.  The  graduation  should 
be  extended  to  each  end. 

588.  A set  of  ring-gauges,  large,  medium,  and  small,  for 
inspecting  the  projectiles  used  in  proof. 

589.  A small  heam-caUper,  with  outside  edges,  for  examin- 
ing the  adjusting-rings  and  the  ring-gauges. 

The  measures  are  to  be  taken  by  scales  corresponding  with 
the  standard  measures  of  the  United  States. 

If  tw'O  or  more  cavities  should  be  near  each  other  on  the 
exterior,  the  gun  may  be  rejected,  though  the  cavities  should  be 
of  less  depth  than  tolerated  in  the  table.* 

590.  If  the  trunnions  are  placed  within  the  Ihnits  of  tolera- 


Fig.  93.— Templates  for  Sight-masses. 


the  base-line  and  the  front 
of  the  rear  sight-mass,  that 
at  the  end  of  the  cascabel, 
the  bevel  of  the  breeching- 
hole,  the  opening  of  the 
cascabel,  and  the  shape  of 


* Ordnance  Instructions. 


INSPECTION  OF  GUNS. 


1S9 


tion,  the  preponderance  must  not  vary  more  than  five  per  cent., 
more  or  less,  from  that  fixed  in  the  contract. 

591.  Impkessiox-t AKER  ' FOE  Yents. — This  consists  of  a 
wooden  head,  one  half  of  which  is  cylindrical,  and  the  other 
half  is  of  the  shape  of  the  chamber,  both  being  rather  smaller 
than  the  parts  of  the  bore  for  which  they  are  intended.  A 
staff,  fiat  on  its  tipper  sides,  and  rounded  on  its  niider  side  to  fit 
the  curve  of  the  bore,  is  mortised  into  the  cylindrical  portion  of 
the  head.  A mortise  is  cut  through  the  chamber  part  of  the 
head,  extending  several  inches  in  rear  and  front  of  the  position 
of  the  vent.  Into  this  mortise  a loose  piece  is  fitted,  capable  of 
free  motion  upwards  and  downwards,  the  top  of  which  is  pierced 
with  holes  to  secure  the  wax  or  composition  which  is  spread  over 
its  surface.  This  movable  piece  rests  on  a wedge  attached  to  a flat 
rod  running  through  a slot  in  the  head  ; there  is  a slot  in  this 
rod  about  four  inches  long,  a pin  passing  through  it  into  the  staff. 

592.  Use. — To  use  the  instrument,  withdraw  the  rod  as  far 
as  the  slot  will  permit,  which  will  allow  the  movable  piece  upon 
which  the  composition  has  been  spread  to  drop  below  the  sur- 
face of  the  head,  and  protect  it.  Push  the  head  to  the  bottom 
of  the  chamber  and  arrange  the  position  of  the  staff,  so  that  the 
movable  piece  will  cover  the  vent,  then  press  the  end  of  the  rud 
home.  This  motion  will  throw  out  the  composition,  an  ! a dis- 
tinct impression  of  the  vent  and  of  fire-cracJcs  (should  there  be 
any)  will  be  left  upon  its  surface  ; draw  the  rod  back  as  far  as 
the  slot  will  allow,  and  withdraw  the  instrument ; the  impression, 
being  protected  thereby,  will  come  out  uninjured.  Impressions 
of  injuries  or  cavities  in  the  bore  may  easily  be  taken  by  a simi- 
lar contrivance. 

593.  Gutta-percha  Iaipressions.— Impressions  are  also 
taken  of  the  interior  of  the  bores  of  cannon  on  softened  strips 
of  gutta-gercha. 

The  following  method  is  used  in  the  English  Service  : * 

A set  of  instruments  are  jirovided  consisting  of  a semi-cylin- 
drical iron  frame,  about  two  feet  long,  connected  with  an  iron 
tube  in  such  a manner  that  by  screwing  up  a rod  which  passes 
through  the  tube,  the  frame  can  be  worked  up  or  down  ; upon 
this  frame  an  iron  plate,  corresponding  to  each  calibre  of  gun,  is 
screwed,  and  when  an  impression  is  taken  gutta-percha  is  spread 
on  the  plate,  and  by  means  of  the  rod  is  pressed  against  the 
defective  part. 

591.  In  the  absence  of  special  instruments  for  the  purpose, 
the  following  method  may  be  used  : 

* Text-book  of  Eifled  Ordnance. 


190 


NAVAL  OEDNANCE  AND  GUNNERY. 


The  blocks  of  wood,  as  shown  in  Fig.  95,  are  of  a wedo-e- 
shape,  they  can  be  made  by  any  carpenter,  but  re'juire  some 
practice  to  work  with  them  so  as  to  get  perfect  impres- 
sions. 


Breech-loaders. 

A 


Muzzle-loaders. 


Fig.  95.— Wood  Blocks  for  taking  Impressions  of  the  Bores  of  Guns. 

The  blocks,  A,  tapering  from  the  centre  for  breech-loading 
guns,  and  from  the  breech  for  muzzle-loading  guns,  -\rfth  their 
wedges,  B,  should  be  made  to  suit  the  diameters  of  the  bores  to 
be  taken,  leaving  room  for  about  .25  incli  of  gutta-percha,  when 
the  wedge  or  wedges  are  driven  home,  and  proceed  to  take  the 
impression  as  follows : 

A sufficient  quantity  of  gutta-percha,  having  been  softened 
in  water  just  below  the  boiling-point,  is  well  kne.ided  and 
worked  to  expel  the  air  and  water,  and  is  laid  along  the  block, 
A,  which  has  been  previously  prepared  by  rubbing  it  over  with 
a little  soft' soap. 

The  gun  is  so  placed  that  the  impression  required  will  be 
taken  upwards,  the  block.  A,  is  inserted  into  the  bore,  and  the 
wedge,  B (if  a breech-loading  gun,  by  simultaneous  blows  at 
both  ends),  is  driven  well  home  with  mauls ; a small  wedge,  C, 
is  then  forced  between  the  ends  of  the  blocks  A and  B. 

This  can  be  easily  withdrawn  in  about  ten  ortifteen  minutes, 
according  to  the  weather,  when  the  impression  has  become  cold, 
and  thus  gi\  es  slackness  to  the  wedge,  B,  and  the  block.  A, 
which  are  withdrawn  in  the  order  named,  together  with  the 
impression,  which  can  be  readily  removed  from  the  block,  being 
prevented  from  sticking  by  the  soft  soap. 

Before  impressions  are  taken  the  bore  should  be  clean,  but 
slightly  greasy ; if  quite  dry  the  gutta-percha  will  adhere  to  it. 


INSPECTION  OF  GUNS. 


191 


and  the  impression  he  damaged  in  the  removal.  The  impres- 
sion shoidd  be  reduced  to  the  smallest  dimensions  compatible 
with  showing  the  whole  of  the  defect. 

595.  The  impressions  of  any  defects  are  cut  off,  the  position 
in  the  gun  is  marked  on  the  back,  and  they  are  registered  and 
preserved  for  future  reference. 

The  defects  are  noted  in  the  following  manner : 

The  distance  is  recorded  in  inches  from  the  muzzle,  and  the 
position  round  the  gun  is  recorded  in  all  cases  according  to  the 
diagram  (Fig.  96),  looking  from  the  muz- 
zle, as  “ up,”  “ D,”  “R,”  “ L,”  or  in  inter- 
mediate positions,  as  “ R of  D,”  “ L of  up,” 
etc.,  etc.  If  a defect  extends  any  length  it 
is  noted  as  in  the  follov/ing  examples  : “ 36 
in.,  D to  L,”  which  means  a defect  thir- 
ty-six inches  from  the  muzzle  running 
roimd  the  bore  from  “ down  ” to  “ left ; ” 
or  “49  inches  to  56  in.  up,”  meaning  a 
defect  running  along  the  top  of  the  bore 
from  forty-nine  inches  to  fifty-six  inches; 
or,  in  other  words,  seven  inches  long. 

5t)6.  Yent  IirPEESsioNS. — The  implements  required  for  tak- 
ing permanent  vent  impressions  in  lead  are  a soft  wire  about 
0.07  in.  in  diameter,  and  3 or  4 fathoms  long. 

A lever  about  twice  the  length  of  the  bore,  about  3 inches 
in  diameter,  and  shod  to  suit  the  curve  of  the  bore  nearly.  A 
small  hutton  of  soft  lead,  judged  to  be  of  sufficient  size  to  fill 
the  vent  at  least  one  inch  from  the  bore.  This  is  to  be  pierced 
lengthwise  to  receive  the  wire. 

597.  To  Take  the  Impression. — Shove  the  wire  through  the 
vent ; let  it  pass  along  tlie  bore  and  out  at  the  muzzle ; put  it 
through  the  leaden  button  and  tie  a knot  at  the  end. 

Draw  the  wire  back  through  the  vent  until  the  leaden  but- 
ton is^  mtroduced  firmly  into  the  inner  orifice.  Apply  the 
lever,  making  its  shoe  bear  on  the  button,  and  force  it  well  in 
by  repeated  blows,  the  muzzle  being  the  fulcrum.  This  done, 
disengiige  the  button  by  pushing  in  the  priming-wire. 

In  taking  impressions  of  the  vent  and  cracks,  each  button 
in  turn  is  used  as  a pattern  for  molding  its  successor,  allowing 
for  the  progressive  enlargement  of  the  vent  or  the  cracks  ema- 
nating from  it.  When  the  crack  shows  itself,  the  head  of  the 
button  should  bo  so  enlarged  as  to  include  it. 

These  examinations  should  take  place  after  every  twenty 
fires,  at  least,  and  more  frequently  when  any  unusual  enlarge- 
ment of  the  vent  or  extension  of  cracks  are  developed,  and  indi- 


192 


NAVAL  ORDNANCE  AND  GUNNERY. 


cate  its  speedy  destruction.  Before  each,  examination  tlie  bore 
of  the  gun  is  carefully  washed  and  dried. 

598.  PowDER-PEOOF.— The  powder-proof  is  based  on  the 
highest  charge  which  the  gun  will  fire  in  service,  and  bears  a 
certain  relation  to  it. 

The  proof-charges  are  as  follows  : 


CALIBRE  AND 

CLASS  OF  GUN. 

CHARGE  OF 
POWDEli,  LBS. 

PROJECTILE. 

yo.  OF 

FIRES. 

Founds. 

( 35 

Shell 

330  lbs. 

3 

XV-inch 

. .48,000  lbs. 

^ 45 

U 

. 

u 

|> 

I 55 

Cored  Shell 

400 

“ 

3 

Xl-indi. . . 

..10,000  “ 

(25 

( 

Solid  Shot 

Shell 

100 

127 

(( 

(( 

1 

10 

X-inch . . . . 

..12,500  “ 

jl8 

112 

Sohd  Shot 

Shell 

124 

05 

U 

ii 

1 

10 

IX-inch.... 

...9,000  “ 

jl5 

(10 

Solid  Shot 

Shell 

90 

08 

u 

1 

10 

Vlll-inch  of. . 

...0,500  “ 

10 

Shot 

, 65 

(( 

10 

32-pdr.  of  . . . 

...4,500  “ 

8 

Shot 

32 

(( 

10 

The  cannon-powder  for  pi’oof  is  of  not  less  than  1,500  feet 
initial  velocity.  It  is  tilled  in  service-cylinders  and  well  settled. 

For  chambered  pieces  the  increased  charges  should  fill  the 
chamber  and  necessary  portion  of  the  bore. 

The  projectiles  are  of  full  weight,  and  not  below  the  mean 
gauge ; the  shells  filled  with  a mixture  of  sand  and  ashes,  to 
'bring  them  up  to  the  weight  of  the  filled  shells.  Sabots  for 
the  shell,  and  a grommet  wad  over  the  shot. 

The  gun  should  be  fired  on  skids  or  a proving-carriage  to 
test  the  trunnions. 

If  five  per  cent,  out  of  any  lot  offered  for  ordinary  proof 
under  a contract  fails  to  sustain  it,  the  whole  may  be  rejected, 
as  may  be  stipulated  in  the  contract. 

599.  Water-pkoof. — The  pressure  to  be  applied  in  the 
water-proof  is  two  atmospheres,  or  thirty  pounds  to  the  square 
inch. 

The  penetration  of  water  in  this  proof  through  the  metal 
of  the  piece,  in  any  place,  will  cause  the  rejection  of  the  gun  ; 
and  if,  on  examination  after  the  water-jjroof,  there  are  any 
defects  indicated  by  weeping  or  dampness  in  the  bore,  the  gun 
is  rejected. 

The  water-proof  is  alone  to  be  depended  on  to  detect 
minute  clusters  of  cavities  in  the  bore,  which  for  this  jiurpose 


INSPECTIOjST  of  guns. 


193 


should  be  perfectly  dry,  and  examined  by  sunlight.  All  in- 
spections, consequently,  sliould  take  place  in  fair  weather,  and 
when  the  temperature  is  above  the  freezing-point. 

600.  IlydmuliG  Pump  and  Apparatus  for  the  water-proof, 
— Any  of  the  various  patterns  of  this  macliiue  may  be  applied 
to  the  proof  of  guns.  An  iron  cross-head  is  secured  to  a stout 
wooden  block  which  fits  into  the  muzzle,  and  which  has  a 
flange  or  shoulder  to  cover  the  muzzle-face ; rings  of  gutta- 
percha are  plncecl  between  them ; an  iron  rod  with  a ring  in 
one  end,  to  lit  over  the  trunnion,  and  with  a thread  cut  on  the 
other  end,  is  used  on  each  side  of  the  gun,  to  connect  the  trun- 
nions with  the  cross-head.  The  whole  is  set  up  Avith  nuts,  and 
the  pressure  on  the  rings  makes  a tight  joint ; a coupling  on 
the  cross-head  receives  the  hose,  and  the  water  is  forced  into 
the  gun  through  a hole  in  the  Avooden  block.  Care  should  be 
taken  that  the  valve  is  loaded  Avith  the  proper  Aveight  for 
proof. 

In  the  construction  of  the  huilt-tcp  steel-lined  cannon  of  the 
English  service,  the  steel  tubes  are  subjected,  after  toughening 
in  oil,  to  a water-pressure  in  the  interior  of  8,000  lbs.  per 
square  inch,  to  detect  any  latent  cracks  ; and  after  the  powder- 
proof  they  are  subjected  to  a presstire  of  120  lbs.  on  the  square 
inch,  to  make  sure  that  the  end  has  not  been  split  at  proof. 

601.  Extreme  Pkoof  of  Tkial-gujsts.— The  extreme  proof 
of  guns  intended  for  trial  of  metal  is  conducted  as  follows  : 

A suitable  butt  is  erected  to  arrest  the  flight  of  the  projectiles 
used  in  proof,  and  to  admit  of  their  easy  recoAmry,  and  a bomb- 
proof, readily  accessible,  for  the  protection  of  the  tiring-party. 

After  undergoing  the  ordinary  proof  established  for  its 
calibre'  and  class,  the  gun  selected  for  extreme  proof  is  subjected 
to  at  least  1,000  rounds  Avith  service-charges. 

It  may  be  tired  from  skids  or  suspended. 

During  the  trial  the  gun  is  frequently  and  critically  exam- 
ined, inside  and  out,  for  cracks  or  defects,  especially  about  the 
interior  orifice  of  the  A^ent,  of  which  impressions  are  taken  in 
Avax  at  regular  intervals. 

If  they  show  that  the  vent  is  corroded  in  furroAvs,  and  en- 
larged considerably  in  diameter  at  its  juncture  with  the  bore,  a 
permanent  impression  is  to  be  taken  in  lead,  to  show  the 
conical  enlargement. 

602.  Enlargement  of  Yents. — When,  from  the  appear- 
ance of  the  bore  at  the  interior  orifice  of  the  vent,  it  is  evident 
that  the  latter  has  enlarged  beyond  the  limit  of  safety,  and  es- 
pecially Avhen  a crack  or  cracks  appear  to  be  extending  rapidly, 
the  vent  so  enlarged  may  be  filled  with  melted  tin  or  zinc ; a 

13 


194 


NAVAL  OEDNANCE  AND  GUNNEKT. 


tiglit-fitting  sponge-liead  being  pnsbed  to  tbe  bottom  of  the 
cbamber  to  close  the  interior  orifice — and  the  other  vent  bein'^ 
drilled  through  for  the  pui-pose  of  continuing  the  firing.  The 
precise  time  at  which  this  is  to  be  done  will  vary  according 
to  circumstances ; such  as  quality  of  metal,  charge,  and  eleva- 
tion. 

603.  The  endurance  of  a smooth-bored  gun  with  seiwice- 
charges  may  be  surely  predicted  by  oljservation  of  the  progres- 
sive wear  of  the  interior  orifice  of  the  vent.  There  are  certain 
general  forms  in  which  this  enlargement  takes  ]3lace.  They 
may  be  classed  as  triangular,  lozenge,  quadrilateral,  star,  circu- 
lar, and  elliptic.  (See  Plates  in  Ord.  Ins.) 

With  the  lateral  vent  of  the  Dahlgren  system,  it  usually 
takes  the  lozenge  form'^  the  cracks  extending  from  the  opposite 
angles  lengthwise  of  the  bore. 

AVith  those  rifled-cannon  in  which  the  vent  is  bouched,  the 
cracks  appear  around  the  bouching,  and  although  the  bouching 
preserves  the  vent,  yet  the  formation  of  fissures  around  the  en- 
larged orifice,  when  once  commenced,  causes  a greater  tendency 
to  rapture.  AYith  the  vent  not  bouched,  the  wear  in  rifle-can- 
non is  about  double  that  of  the  smooth  bore. 

So  long  as  the  wear  of  the  vent  is  regular  and  without 
cracks,  a mere  enlargement  is  not  indicative  of  danger;  but 
when  it  reaches  a diameter  of  four-tenths  of  an  inch,  the  vent 
should  be  closed  and  a new  one  opened. 

604.  A gun  of  ^ large  calil^re  should  not  in  service  be 
expected  to  stand  more  than  400  or  500  rounds  before  it  will 
be  necessary  to  open  the  new  vent,  which,  ho^rever,  Avill  be  of 
no  advantage  unless  the  old  one  be  closed  at  its  interior  orifice, 
on  which  the  gases  otherwise  would  continue  to  act  as  a wedge. 

The  first  distinct  appearance  of  the  cracks,  as  shown  by  the 
button,  is  the  proper  limit. 

After  the  gun  bursts,  a sketch  or  draft  is  made  showing  the 
lines  of  fracture,  and  specimens  are  reserved  for  trial  of 
density  and  tensile  strength ; and,  if  practicable,  a photograph 
is  taken. 

605.  Exdtjeakce  of  Guxs  in  Service. — The  principal  in- 
juries caused  by  service  are  internal,  arising  from  the  separate 
action  of  the  powder  and  the  projectile.  They  increase  in 
extent  with  the  calibre,  whatever  may  be  the  nature  of  the  gun, 
but  are  modified  by  the  material  of  Avhich  it  is  made. 

606.  In,iueies  from  the  Powder. — The  injuries  from  the 
powder  generally  occur  in  rear  of  the  projectile.  They  are, 
1st.  Enlargement  of  that  portion  of  the  bore  vdiich  contains 
the  poAvder,  arising  from  the  compression  of  the  metal.  This 


INSPECTION  OF  GUNS. 


195 


injury  is  more  marked  when  a sabot  or  wad  is  placed  between 
the  powder  and  tlie  projectile,  and  is  greatest  in  a vertical 
direction.  2d.  Cavities  produced  Ijy  the  melting  away  of  a 
portion  of  the  metal  by  the  beat  of  combustion  of  the  charge.^ 
3d.  Cracks  arising  from  the  tearing  asunder  of  the  particles  of 
the  metal  at  the  surface  of  the  bore.  At  first  a crack  of  this 
kind  is  scarcely  perceptible,  but  it  is  increased  by  continued 
firmg  until  it  extends  completely  tbrougb  the  side  of  the  piece. 
It  generally  commences  at  the  junction  of  the  chamber  with 
the  bore,  as  this  portion  is  less  supported  than  the  others.  4th. 
Furrows  or  scoring  produced  by  the'  erosive  action  of  the 
inflamed  gases.  Tliis  injury  is  most  apparent  where  the  cur- 
rent of  the  gas  is  most  rapid,  oi‘  at  the  interior  orifice  of  the 
vent,  and  on  the  surface  of  the  bore,  immediately  over  the  seat 
of  the  projectile. 

607.  Scoring  commences  very  early  in  large  guns  ; at  first, 
it  is  only  a mere  roughness,  which  gradually  increases  in  depth 
and  forms  lines  along  the  bore ; but  it  is  not  until  a gun  has 
been  fired  very  considerably  that  it  becomes  of  importance. 

The  impressions  of  deep  scoring  resemble  the  bark  of  an  old 
elm-tree,  the  metal  being  eaten  awtay  into  irregular  furrows  and 
ridges.  Even  when  it  has  reached  this  extreme  case,  however, 
scoring  has  not  caused  the  destruction  of  the  gun,  though  in 
some  instances,  acting  like  a wedge,  it  has  split  the  bore  at  that 
part. 

Some  experimental  guns,  excessively  scored  on  the  upper 
side  of  the  bore,  have  been  turned  over,  vented  and  sighted  on 
the  under  side,  but  this  has  not  been  found  necessary  until  the 
gun  has  been  used  more  than  is  probable  under  ordinary  cir- 
cumstances. 

608.  Injuries  feow  the  Projectile.— The  injuries  ailsing 
from  the  action  of  the  projectile  occur  around  the  projectile  and 
in  front  of  it.  They  are  : 

1st. — Indentation  in  the  lower  side  of  the  bore,  pro- 
duced by  the  pressure  on  the  projectile  by  the  escape  of  gas 
through  the  windage,  before  the  ball  has  moved  from  its 
seat.  The  elasticity  of  the  metal,  and  the  burr,  or  crowd- 
ing up,  of  the  metal  in  front  of  the  projectile,  cause  it  to 
rebound,  and,  being  carried  forward  by  tlie  force  of  the  charge, 
to  strike  against  the  upper  side  of  the  bore,  a short  distance  in 
front  of  the  trunnions.  From  this  it  is  reflected  against  the 
bottom,  and  again  reflected  against  the  top  of  the  bore,  and  so 
on  until  it  leaves  the  piece. 

The  first  is  called  “ indentation,”  and  the  others  are  called 
“ enlargements.” 


196 


NAVAL  ORDNANCE  AND  GITNNERT. 


In  pieces  of  ordinaiy  length,  there  are  generally  three  en- 
largements when  this  injury  tii'st  makes  its  appearance,  but 
their  number  is  increased  as  the  “indentation  ” is  depressed  and 
the  angle  of  incidence  increased.  The  effect  of  this  bounding 
motion  is  alternately  to  raise- and  depress  the  y^iece  in  its  trun- 
nion-holes, and  to  diminish  the  accuracy  of  fire,  until  finally 
the  piece  becomes  unfit  for  service. 

It  is  principally  from  this  injury  that  bronze  guns  become 
unserviceable.  Mortars  and  howitzers  are  not  much  affected 
by  it. 

The  principal  means  used  to  prevent  this  injury  are  to  wrap 
the  projectile  with  cloth  or  paper,  and  to  shift  the  seat  of  the 
projectile.’  v. 

The  latter  may  be  done  by  a wad  or  lengthened  sabot,  or  by 
reducing  the  diameter  and  increasing  the  length  of  the  cartridge. 
The  last  of  these  methods  is  considered  tlie  most  practical  as 
well  as  the  most  effective  ; and  it  has  the  additional  advantage 
of  decreasing  the  strain  on  the  bore,  by  increasing  the  space  in 
which  the  charge  expands  before  the  ball  is  moved. 

2d.  Scratches  or  furrows  made  upon  the  surface  of  the 
bore  by  rough  projectiles,  or  by  case-shot. 

3d.  Cuts  made  by  the  fragments  of  projectiles  which  break 
in  the  bore. 

4th.  AVearing  away  of  the  lands  of  rifle-cannon,  especially 
at  the  dividing  edges.  A little  rubbing  of  the  side  of  the 
grooves  from  the  filction  of  hard  bearings  is  of  little  importance. 

5th.  Enlargement  of  the  muzzle,  arising  from  the  forcing 
outAvard  of  the  metal  by  the  strikiiig  of  the  projectile  against 
the  side  of  the  bore  as  it  leaves  the  piece.  By  this  action  the 
shape  of  the  muzzle  is  elongated  in  a vertical  direction. 

Gth.  Cracks  on  the  exterior.  Tliese  arc  formed  by  the  com- 
pression of  the  metal  Avithin,  generally  at  the  chase,  where  the 
metal  is  thinnest.  This  portion  of  a bronze  gun  is  the  first  to 
give  Avay  by  long  firing,  Avhereas  cast-iron  guns  usually  burst  in 
fear  of  the  trunnions,  and  the  fracture  passes  through  the  vent, 
if  it  be  much  enlarged. 

609.  Dkscriptiv]':  List  of  Guxs. — Before  sailing,  the  In- 
spector of  Ordnance  furnishes  the  Commander  with  a descrip- 
ti\  e list  of  his  battery,  together  with  a statement  of  the  number 
of  times  each  gun  on  board  has  been  fired,  in  the  following 
form  (a  copy  of  Avdiieh  the  Commander  transmits  to  the  Bu- 
reau of  Ortlnance  before  sailing;  this  list  is  returned  to  the  In- 
spector of  the  yard  to  which  she  may  return,  Avith  all  additional 
firing,  noted  opposite  the  number  of  each  gnu,  certified  correct 
by  the  Commander) ; 


INSPECTION  OF  GUNS, 


197 


Class  of 

Marks  on  ba.se-ring. 

Trunnions. 

Pivot  or 

' 

Where 

No.  of  fires 

Gun. 

Kegr.  No.  j Weight. 

Fouatiry. 

Right. 

Left. 

Broadside. 

Received. 

to  date. 

610.  Set  of  Vent  Impressions. — The  Inspector  also  fur- 
nishes the  Commander  with  a set  of  leaden  impressions  of  the 
interior  orifice  of  the  vents  of  the  guns,  secured  in  a suitable 
box,  that  he  may  be  able  to  compare  the  wear  and  gradual  en- 
largement. These  are  transferred  with  the  guns  to  other  ships, 
or  when  landed.  (Fig.  97.) 

611.  Inspection  at  Termination  of  a Cruise. — At  the  ter- 
mination of  a cruise  the  guns  are  carefully  examined  by  the 
Ordnance  Officer  of  the  Yard,  and  such  others  as  may  be  di- 
rected, with  the  view  to  discover  and  report  any  injuries  which 
they  may  have  sustained  in 
service,  or  any  defects 
which  may  not  have  been 
developed  in  the  original 
■proof. 

Before  proceeding  to  ex- 
amine a gun  the  bore  should 
be  thoroughly  cleaned;  it 
will  generally  be  sufficient- 
ly prepared  for  examina- 
tion by  washing,  sponging, 
and  drying. 

If,  however,  there  be 
hard  rust  or  a coating  of 
any  kind  on  the  surface  of 
the  bore,  it  may  be  cleansed  either  by  firing,  if  circumstances 
admit,  one  or  two  scaling-charges,  about  one-third  the  full 
charge,  without  projectiles,  which  will  usually  loosen  the  scale ; 
or  the  bore  may  be  scrubbed  out  with  hot  water  and  potash. 

Ho  sharp-edged  or  pointed  scraper  should  be  employed  for 
cleansing  the  bores  of  rifled-guns,  as  they  are  unnecessary  and 
liable  to  injure  the  rifling. 

612.  In  this  examination  the  attention  of  the  Inspecting 
Officers  is  directed  to  the  following  points,  viz. : 


Fig.  97. — Vent  Impressions. 


198 


NAVAL  ORDNANCE  AND  GUNNERY. 


Enlargement  of  the  interior  orifice  or  exterior  orifice  of  the 
vent. 

Indentations  or  hollows  produced  by  the  projectile  Ijollot- 
ing  against  the  surface  of  the  bore,  or  by  the  action  of  the 
gases. 

Cuts  or  scratches  in  the  bore,  produced  by  fragments  of 
broken,  or  roughness  of  imperfect,  projectiles. 

Roughness  or  corrosion  of  the  metal  on  the  exterior,  pro- 
duced by  neglect  or  exposure. 

Similar  injuries  in  the  bore,  or  any  enlargement  of  the  bore, 
which  is  to  be  ascertained  by  measuring  with  the  star-gauge,  at 
every  one-fourth  of  an  inch,  from  the  bottom  of  the  cylindrical 
part  to  the  seat  of  the  projectile,  every  inch  from  that  point  to 
the  trunnion,  thence  every  five  indies  to  the  muzzle,  and  the 
results  recorded  in  the  usual  form,  and  reported  to  the  Bui-eau, 
that  they  may  be  compared  with  those  noted  at  the  original  in- 
spection. 

In  rified-cannon,  cracks  or  injuries  produced  by  firing,  or  the 
mpture  of  shells,  are  to  be  sought  for,  around  and  in  the  rear 
of  the  vent  bouching ; on  the  top  of  the  bore,  between  the 
trunnions  and  reinforce-band  ; on  the  lower  side  of  the  bore, 
near  the  seat  of  the  projectile,  at  the  junction  of  the  lands  and 
the  grooves ; near  the  inside  of  the  muzzle,  caused  by  explosion 
of  shells. 

Care  is  to  be  taken  that  the  distinguishing  marks  and  num- 
bers are  always  accurately  noted,  that  the  correct  history  of  each 
gun  may  be  preserved. 

613.  Inspection  of  Vents.  — As  the  best  indication  of  the 
amount  of  fii'ing  to  which  any  smooth-bored  gun  has  been  ex- 
posed, when  it  is  not  otherwise  known,  is  given  by  the  enlarge- 
ment of  the  vent ; particular  attention  is  paid,  in  the  re-inspection 
of  the  guns,  to  this  point.  The  standard  gauge  is  used  to  ascer- 
tain the  general  enlargement,  and  the  searcher  to  detect  defects 
which  may  have  been  developed  in  firing.  Impressions  are 
taken  of  the  lower  orifice  of  the  vent  with  softened  wax,  and  if 
they  show  that  the  vent  is  corroded  in  furrows  and  enlarged 
considerably  in  diameter  at  its  junction  with  the  bore,  a perma- 
nent impression  is  to  be  takeli  in  lead  to  show  the  conical  en- 
largement. 

01-1.  When  the  number  of  rounds  fired  is  not  known,  an 
estimate  may  be  made  from  an  examinaiion  of  the  vent  by  cy- 
liudricad  gauges,  difl'eriug  from  each  other  by  .01  inch,  passed 
through  it. 

In  all  the  guns  of  the  Dahlgren  pattern  the  vents  are  two- 
tenths  of  an  inch  in  diameter. 


INSPECTION  OF  GUNS. 


199 


Observation  of  the  wear  of  the  vent  in  proof-firing  of 
smooth-bored  guns  gives  tlie  following  as  the  average  diameter 
of  the  vent,  after  the  under-mentioned  number  of  fires : 

No.  of  Eounds 100,  200,  300,  400,  500. 

Diameter  of  Vent 24,  .26,  .30,  .35,  .40. 

These  combined  with  examination  of  the  interior  orifice, 
will  enable  a very  correct  judgment  to  be  formed  of  the  proba- 
ble number  of  fires  sustained  and  duration  of  the  gun. 

The  larger  the  calibre  and  the  heavier  the  charge,  the  more 
promptly  the  wear  is  manifested  on  the  interior  and  exterior. 

The  enlargement  does  not  extend  very  far  from  the  lower 
orifice  until  the  enlargement  of  the  exterior  has  reached  a di- 
ameter of  .3  of  an  inch.  So  long  as  the  wear  is  regular,  and  the 
cracks,  although  numerous,  do  not  exceed  .5  of  an  inch  in 
length,  the  indications  are  good.  If  the  cracks  are  but  few  or 
diminish  in  number,  running  into  each  other  and  extending 
rapidly,  it  is  a very  unfavoi’able  sign.  In  the  rifie-cannon  (Par- 
rott’s) cracks  athwart  the  bore,  either  running  into  the  benching 
or  into  the  rear  of  it,  are  very  unfavorable  to  the  gun’s  endu- 
rance. 


CHAPTEE  lY. 


BUILT-UP  GUNS.* 

Section  I-^Princijples  of  Construction. 

615.  GEYEEAL  COJ^SIDEEATIOISrS. — modern  the- 
ory of  constructing  guns  can  be  called  new,  since  guns  are  in 
existence  that  have  been  either  recovered  from  wrecks,  or  pre- 
served in  other  ways,  showing  every  variety  of  coils,  hoops, 
casting,  wire-binding,  and  so  on,  as  far  as  the  appliances  then 
in  use  could  furnish  the  quondam  inventors  with  means  of  car- 
rying their  inventions  into  effect. 

That  in  which  novelty  has  been  attained,  is  the  improve- 
ment of  processes  by  which  large  castings  or  forgings,  accurate 
turning  and  boring,  can  be  secured,  or  by  which  chemical 
knowledge  can  be  brought  to  bear  on  the  manipidation  of 
metals  ; but  no  such  progress  can  make  a built-up  gun,  or  ma- 
chine of  any  sort,  stronger  than  a perfectly  homogeneous  one, 
in  which  the  varying  strains  are  closely  calculated  and  properly 
met  by  the  scientific  disposition  of  the  necessary  strength. 

616.  DEFINITION. — The  terms  ‘■^huilt-vp’’^  and  ‘•'hoojped'' 
are  applied  to  those  cannon  in  which  the  principal  parts  are 
formed  separately,  and  then  united  in  a peculiar  manner.  They 
are  not  necessarily  composed  of  more  than  one  kind  of  metal ; 
some  of  the  most  important  are  made  of  steel  alone ; and  they 
may  be  made  by  welding  or  by  screwing  the  parts  together,  and 
by  shrinking  oi’  forcing  one  part  over  another. 

617.  OBJECT. — The  object  of  this  method  of  manufacture 
is  to  correct  the  defects  of  one  material  by  uniting  with  it  op- 
posite qualities  of  the  same  or  other  materials.  The  defects 
Avhich  follow  tlie  working  of  large  masses  of  iron  or  steel,  such 
as  crystalline  structure,  false  welds,  cracks,  etc.,  are  avoided  by 
first  forming  the  parts  in  small  masses  of  good  quality  and  then 
uniting  them  separately. 

618.  Nature  of  the  Eokce  to  be  kestkatned. — In  consider- 
ing the  effect  upon  a yielding  material  of  any  force  which  may 
be  applied,  the  rate  of  application  of  the  force,  or  the  time 
which  elapses  from  the  instant  when  the  force  begins  to  act, 
until  it  attains  its  maximum,  should  not  be  neglected;  for,  with 
equal  ultimate  pressures  per  square  inch  of  surface,  that  force 

* Compiled  by  Lieutenant  J.  C.  Solcy,  U.  S.  Na\y. 


il 


BiriLT-UP  GUNS. 


201 


■will  be  most  severe  upon  the  gun  which  attains  this  pressure 
in  the  shortest  period  of  time.  (Chap.  II.) 

619.  HOW  TO  INCREASE  THE  STRENGTH  OF  A 
GUN. — The  most  obvious  method  of  enabling  a gun  to  sustain 
a greater  elastic  pressure  is  simply  to  thicken  its  side?,  thus  in- 
creasing the  area  of  the  parts  to  be  torn  asunder.  This  rule  has 
been  found  to  work  practically  with  guns  of  small  calibre,  but 
in  larger  guns  it  does  not  work,  from  the  fact  that,  in  cast  guns, 
of  whatever  metal,  the  outside  helps  but  very  little  in  restrain- 
ing the  explosive  force  of  the  powder,  the  strain  not  being 
communicated  to  it  by  the  intervening  metal.  The  consequence 
is  that,  in  large  guns,  the  inside  is  split  while  the  outside  is 
scarcely  strained.  This  split  rapidly  increases,  and  the  gun 
ultimately  bursts. 

620.  Example.  — If  we  make  equidistant  ch’cular  marks  on 
the  end  of  an  India-rubber  cylinder  (Fig. 

98),  and  stretch  if, 
we  can  plainly  see 
how  much  more 
the  inside  is 
strained  than  the 
outside,  or  even 
the  intermediate 
parts ; the  spaces 
between  the  marks 
will  become  thin- 
ner, each  space  he- 
coming  less  than 
that  outside  of  it ; 
but  the  inner  spaces,  much  thinner  than 
the  others  (Fig.  99),  showing  that  when 
the  inside  is  strained  almost  to  breaking, 
the  intermediate  parts  are  doing  much  less  work,  and  those  far 
removed  almost  none. 

621.  Limit  to  TnicKisrEss  of  Metal. — Now,  if  we  take  any 
transverse  section  of  a gun,  any  unit  in  length,  and  suppose 
the  metal  to  be  divided  into  any  number  of  concentric  rings,  it 
will  be  evident  that  the  greater  the  distance  of  any  ring  from 
the  axis  of  the  gun,  the  less  will  it  be  stretched  by  the  expansion 
of  the  bore  when  the  piece  is  discharged,  and  consequently  the 
less  will  it  contribute  to  the  general  strength  of  the  gun.  If  the 
strain  upon  the  bore  from  the  discharge  he  considered  merely 
as  a pressure, — statical  force, — the  resistance  offered  to  it  by  any 
two  rings  will  be  inversely  proportional  to  the  square  of  then* 
cu’ciunferences  or  distances  from  the  axis  of  the  ffun. 


Fig.  98. — India-rabber 
cylinder,  with  equi- 
distant concentric 
marks. 


Fig.  99.  — The  same  cyiin- 
der,  stretched  by  inter- 
nal pressure  ; the  con- 
centric marks  show  the 
inferior  stretch  of  the 
exterior. 


202 


NAVAL  ORDNANCE  AND  GUNNERY. 


G22.  It  will,  therefore,  appear  that  there  is  a certain  limit 
beyond  M'hich  it  would  be  useless  to  increase  the  thickness  of  the 
metal,  viz. ; When  the  force  exerted  on  the  surface  of  the  bore 
would  be  sufficient  to  rupture  the  interior  portions  of  the  metal 
before  the  strain  acted  to  any  extent  upon  the  exterior  parts. 
Any  arrangement  of  the  parts  by  which  the  explosive  strain  is 
distributed  equally  over  the  entire  thickness  of  the  piece, 
necessarily  brings  a greater  amount  of  resistance  into  play.  In 
order  to  obtain  the  requisite  resistance,  and  with  a moderate 
thickness  of  metal,  it  is  desirable  to  equalize,  as  far  as  possible, 
the  strain  upon  every  portion  of  the  metal. 

C23.  METHODS  OF  EQUALIZING  THE  STEAINS. 
— There  are  two  general  methods  of  accomplishing  this,  viz. : 
First,  l)y  giving  the  exterior  portions  a certain  initial  tension, 
gradually  decreasing  and  passing  into  compression  towards  the 
interior,  which  is  done  by  shiinking  heated  iron  bands  or  tubes 
around  the  parts  to  be  compressed,  or  by  slipping  a tube  into 
the  bore,  which  has  been  slightly  enlarged  by  heat. 

Secondly,  by  means  of  the  system  of  varyiluj  elasticity ; 
this  is  accomplished  by  placing  that  metal  which  stretches  most 
within  its  elastic  limit  around  the  surface  of  the  bore,  so  that, 
by  its  enlargement,  the  ex])losive  strain  is  transmitted  to  the 
other  parts. 

These  two  methods  of  ecpializing  strains  without  an  inordi- 
nate increase  of  thickness,  are  so  important  that  they  deserve 
more  than  a passing  notice.  They  are  called  tire  systems  of  In- 
itial Tension  and  Varying  Elasticity.  Some  gun-makers  use 
the  one,  some  the  other,  some  a combination  of  the  two,  and 
even  in  our  own  hollow-cast  guns  the  idea  of  Initial  Tension  is 
one  of  primary  importance. 

02i.  PuixciPLKS  OF  System  of  Ixttial  Texsiox. — The  sys- 
tem of  Initial  Tension  consists  in  making  a gun  of  concentric 
tubes,  by  putting  (.m  each  snccessive  layer,  proceeding  outward 
from  the  centre,  with  an  initial  tension  exceeding  that  of  those 
below  it ; in  other  words,  so  that  each  hoop  shall  compress  the 
one  within  it.  The  inner  layer  is  thus  in  compression  while  the 
outer  layer  is  in  the  highest  tension.  The  innei’  layer  is  able  to 
sustain  the  tii’st  and  greatest  stretch,  and  the  outer  layer, 
although  sti'etched  less  by  the  explosion  of  the  powder,  has 
already  been  stretched  into  high  tension,  and  thus  has  to  do  an 
equal  amount  of  work.  The  intermediate  layers  bear  the  same 
relation  to  the  initial  strain,  and  to  the  strain  of  the  powder,  so 
that,  in  short,  all  the  layers  contribute  equally  of  their  tensile 
strength  to  resist  the  strain  of  the  explosion. 

625.  Defects  of  tue  System. — Each  hoop,  or  tube,  has  this 


BUILT-UP  GUNS. 


203 


element  of  weakness  that  its  inner  circumference  is  more 
stretched  than  its  onter  one.  Absolute  perfection  would 
necessitate  infinitely  thin  hoops,  and,  practically,  the  thinner 
the  layei’s  the  greatei'  will  be  the  strength,  provided  the  mechan- 
ical difficulties  in  constracting,  and  more  especially  in  applying, 
a great  number  of  thin  strata  with  the  proper  tension  do  not 
outweigh  the  advantages. 

G26.  M]5thods  of  Application. — The  two  principal  methods 
of  applying  the  system  are  by  shrinliing  on,  or  by  forcing  on, 
the  hoops. 

627.  SJirinldng. — If  the  hoops  are  put  on  by  shrinking,  two 
embarrassments  arise : Firsts  the  hoops  must  be  accurately 
bored,  and  after  each  layer  has  been  put  on,  the  gun  must  be 
put  in  a lathe  and  tlie  outside  turned.  Great  accuracy  of  labor 
is  required — labor  of  tbe  most  expensive  class. 

Secondlg,  the  process  of  shrinking  on  is  not  to  l)e  depended 
upon ; not  only  is  there  a difliculty  in  insuring  the  exact  tem- 
perature required,  but  scai’cely  any  two  pieces  of  iron  will 
shrink  identically.  The  fitting  of  hoops  Avith  nice  adjustment 
Avoiild  be  difficult,  theoretically;  practically,  it  Avould  not  bo 
done.  But  the  chief  embarrassment  is  the  unequal  effect  of 
heat. 

In  the  first  place,  heating  the  layers  over  a fire  to  expand 
them  subjects  one  part  to  more  heat  than  another  ; the  tempera- 
ture of  the  surface  and  interior  are  unequal,  thus  causing 
irregular  strains.  This  may  be  remedied  by  boiling  the  hoops 
in  oil,  Avhich  Avould  toughen  as  Avell  as  expand  the  lioops.  in 
the  second  j)lace,  the  hoops  are  often  heated  to  redness  Avhen 
oxydation  takes  place.  The  internal  diameter  of  the  hoop  is 
increased,  and  scale  is  left  betAveen  some  parts  and  not  betAveen 
others.  In  the  third  place,  cast-iron  and  steel  sensibly  and  per- 
manently eidarge  in  proportion  to  the  amount  of  carbon  they 
contain  Avheii  subjected  to  the  heat. 

628.  Forcing  on. — WhitAvorth  and  Blakely  advocate  the 
method  of  forcing  the  hoops  on  Avith  hydrostatic  pressure.  The 
forcing  of  a slightly  conical  ring  over  a correspondingly  conical 
tube  obviates  the  necessity  of  great  accuracy  in  the  diameter  of 
either  pieces.  The  truth  of  the  cone  depends  upon  the  correct- 
ness of  the  lathe.  Tbe  truth  of  the  surfaces  is  also  a question 
of  good  tools.  The  tension  of  the  ring  depends  on  the  distance 
to  Avhich  it  is  forced  in  the  conical  tube,  and  this  may  be  regu- 
lated by  the  saf ety-Auil ve  of  the  hydrostatic  press.  With  special 
tools,  and  Avhen  correctness  depends  upon  the  mechanical 
appliances,  Avhich  can  be  adjusted  Avith  the  utmost  nicety,  an 
inexpert  Avorkman  could  hardly  fail  to  do  Avell. 


204 


NAVAL  ORDNANCE  AND  GUNNERY. 


629.  Principles  of  Syste^i  of  Yaeting  Elasticity. — Lotus 
now  suppose  the  hoops  or  tubes  forming  a gun  to  be  fitted  to- 
gether accurately,  but  without  tension.  If  the  inner  hoop 
is  very  elastic,  and  the  next  less  elastic,  and  so  on  throughout 
the  series,  the  outer  hoops  being  the  least  elastic,  and  the 
degree  of  elasticity  being  exactly  proportioned  to  the  degree  of 
elongation  by  internal  pressure,  all  the  hoops  will  be  erpially 
strained  by  the  powder,  and  none  of  their  strength  wasted.  If 
the  inner  hoops  be  stretched  by  the  powder-pressure  of  an 
inch,  and  the  outer  hoop  of  an  inch,  the  material  of  the  in- 
ner hoop  should  have  such  elasticity  that  it  should  be  no  nearer 
its  breaking-point  when  stretched  -jL  of  an  inch  than  the  less 
elastic  outer  hoop  when  stretched  -yj-y  of  an  inch.  Both  hoops 
would  then  be  equally  strained  by  the  powder,  and  oppose  an 
equal  resistance  to  it. 

630.  Defects  of  the  System. — It  has  been  found  difficult 
to  obtain  materials  having  the  respective  ranges-  of  elasticity 
necessary  to  perfectly  cany  out  this  system.  For  this  reason 
the  outer  tube  or  tubes  are  sometimes  put  under  an  initial  ten- 
sion equal  to  the  working  load,  in  order  that  the  work  done  may 
be  equal  for  all.  This  severe  and  permanent  strain  on  the 
outer  tube,  of  course,  tends  to  relax  it;  but  if  the  inner  tube  can 
stretch  very  much  without  injury,  and  the  outer  tube  can  only 
stretch  a little,  the  permanent  strain  upon  all  parts  of  the  gun, 
in  order  that  it  may  be  uniformly  strained  under  fire,  will  be 
slight,  and  the  tendency  to  relaxation  limited. 

631.  Longitudinal  Steength. — Care  must  be  taken  to  have 
sufficient  longitudinal  strength.  The  theoretical  resistance  of 
a cylinder  under  internal  pressure  to  cross  fractui-e  is  four 
times  as  great  as  its  resistance  to  splitting  longitudinalh’,  if  the 
tenacity  of  the  metal  is  the  same  in  all  directions.  To  obtain 
strength  in  this  direction,  some  circumferential  strength  may 
be  sacrificed  by  making  one  part  the  length  of  the  entire  gun. 
and  of  adequate  thickness.  It  is  probably  better  that  this 
single  large  piece  should  be  inside,  and  this  is  the  general 
practice. 

632.  Length  of  Hoops. — Hoops  of  considerable  length  are 
desirable  to  add  to  the  frictional  surface,  thus  giving  longitudinal 
strength  to  the  gun.  But  length  or  continuity  is  chiefly  desir- 
able to  transfer  the  strain  upon  one  point  to  a large  resisting 
area. 

633.  Huviber  of  Hoops. — An  obvious  disadvantage  of  a 
large  number  of  hoops  is  that  the  transverse  strength  of  the  gun 
is  much  reduced. 

634.  Want  of  Continuity. — A hooped  gim  must  always 


BUILT-UP  GUNS. 


205 


possess  the  defect  of  want  of  continuity  of  substance.  How- 
ever perfect  the  workmanship  at  first,  in  large  guns  the  jar  of 
repeated  firing  would  soon  shake  them  loose.  The  great  defect 
in  the  Armstrong  guns  Avas  developed  in  the  shaking  loose  and 
fracturing  of  some  of  the  hoops  under  the  tremendous  vibration 
due  to  filing  large  charges. 

635.  Yibeation. — Both  the  means,  that  have  been  con- 
sidered, of  increasing  the  resistance  of  a gun  to  mere  pressure, 
are  perfected  only  in  proportion  to  the  number  of  separate 
tiihes  or  layers  employed ; hut  on  the  other  hand,  increasing 
the  number  of  parts  lessens  the  resistance  of  the  body  - to 
tlie  effect  of  sudden  strain.  When  a gun  is  fired  the  shock  is 
propagated  from  layer  to  layer  in  a wave;  if  the  layers 
are  already  detached  tubes,  the  outer  one  has  no  help  from  the 
rest  in  i-esisting  the  Aubration,  and  the  only  way  to  modify  the 
effect  of  the  Avave  of  force  upon  the  outer  lajmr  is  to  give  that 
layer  great  mass  and  thence  inertia. 

636.  CONCLUSIONS. — To  sum  up  briefly  tlie  principles  of 
gun  construction,  merely  thickening  the  walls  of  a gun  beyond  a 
certain  point  adds  very  little  to  its  resistance  to  internal  pressure. 
A homogeneous  gun,  in  a state  of  initial  repose,  hoAvever  thick  it 
may  be,  cannot  sustain  permanently  a pressure  per  square  inch 
greater  than  the  tensile  strength  of  a square  inch  of  the  metal 
of  Avhich  it  is  conqAosed.  The  reason  is  that  the  inner  layers 
of  metal  are  more  stretched  and  strained  by  an  internal  press- 
ure than  the  outer  layers,  in  the  inverse  ratio  of  the  squares  of 
their  diameters.  Therefore,  the  layers  must  be  placed  under 
such  initial  strain,  or  must  possess  such  A^arying  elasticity  that  all 
parts  of  the  gun  will  he  equally  Avorked  at  the  instant  of  firing. 

Both  these  conditions  are  perfectly  carried  out  in  proportion 
to  the  number  of  separate  layers  or  tubes  thus  treated ; but  the 
AA^ave  of  force  (in  distinction  from  statical  pressure),  and  the 
effects  of  unequal  vibration,  distress  a gun  in  proportion  to  the 
number  of  its  parts,  so  that  the  building-up  principle  cannot  be 
carried  far  Avithout  depriving  the  gun  of  the  necessary  mass  and 
continuity  of  substance. 

637.  The  system  of  hoops  Avith  initial  tension,  although  the- 
oi’etically  perfect  and  an  acknowledged  improvement  in  the 
construction  of  ordnance,  involves  certain  practical  difficulties. 
When  several  thicknesses  of  hoops  are  used,  it  is  difficult  to 
maiiitaiiA  the  proper  longitudinal  strength,  and  it  has  been  found 
that  a gun  composed  of  tAvo  or  three  tubes,  although  not  so 
strong  to  resist  statical  pressure  as  one  composed  of  five  or  six 
tuh<es,  Avould  ]’esist  a greater  number  of  heavy  charges  of  gim- 
poAvder  aud  prove  a more  trusty  weapon. 


206 


NAVAL  OEDNANCE  AND  GUNNERY. 


633.  With  thepresent  materials,  it  would  be  almost  impossible 
to  insure  uniformly  a degree  of  elasticity  in  the  different  layers, 
exactly  proportional  to  their  respective  elongations  under  fire. 
The  Initial  Tension  system,  slightly  modified,  may  be  brought 
to  the  aid  of  the  system  of  Varying  Elasticity.  If  the  internal 
tube  of  a gun  cannot  stretch  to  the  extent  required  without  in- 
jury, placmg  the  external  tube  in  slight  tension  will  remedy  the 
defect ; then  the  inner  tube  will  have  a greater  range  of  safe 
elongation,  and  the  outer  tube  will  take  a greater  share  of  the 
strain . 

Section  II — The  Parrott  Gun. 


639.  General  Description. — The  Parrott  Guns  used  in  the 
United  States  Uavy  are  chiefly  the  100-pdr.  and  60-pdr.  They 
were  fabricated  exclusively  by  Capt.  Parrott,  at  the  West  Point 
Foundry ; none  have  been  manufactured  since  1865. 

The  peculiaidty  consists  in  the  fact  that  the  gun  fs  a cast-iron 
piece  strengthened  by  shrinking  a coiled  hoop  of  wrought-iron 
over  that  portion  of  the  body  which  surrounds  the  charge. 

6-10.  The  Barrel. — The  cast-iron  main  portion,  or  body, 
A (Fig.  100),  is  made  like  any  ordinary  cast-iron  gun,  except 
that  it  is  a little  lighter  at  the  breech.  The  body  of  tjie  lUO- 
pdr.  is  cast  on  a core,  that  of  the  60-pdr.  is  cast  solid.  The 


body  having  been  bored,  has  that  portion  of  its  exterior  which 
is  to  recei\'e  the  reinforce  turned  to  a cylindrical  form,  and 
of  a diameter  about  yU  fo  n foot  larger  than  the  inte- 

rior diameter  of  the  reinforce  when  cold. 

611.  The  Hoop,  B,  is  formed  by  bending  a rectangular  bar 
of  iron  spirally  round  a mandrel  and  then  welding  the  mass  to- 
gether by  hammering  it  in  a strong  cast-iron  cylinder.  In 
bending  the  bar,  the  outside,  becoming  more  elongated  than  the 
inner  one,  is  diminished  in  thickness,  giving  to  the 
cross  section  of  the  bar  a v, -edge-shape  which  pos- 
sesses the  advantage  of  allowing  the  cinder  to  escape 
through  the  opening,  thereby  securing  a mom  per- 
Fi(i.  101.  feet  weld. 


BUILT-UP  GUN’S. 


207 


642.  Placing  the  Pehstfoece. — The  body  is  placed  in 
nearly  a horizontal  position  npon  bearings  which  permit 
it  to  be  rotated  on  its  axis,  and  which  will  permit  the  rein- 
force to  be  put  on  when  sufficiently  expanded  by  heating  it ; a 
pipe  is  introduced  into  the  muzzle  for  conveying  a constant 
stream  of  cold  water  to  the  bottom  of  the  bore.  AV^hen  the  re- 
inforce has  been  properly  heated,  and  so  expanded  as  to  enable 
it  to  pass  loosely  on  to  the  body,  it  is  placed  in  its  position  on 
the  body,  and  cold  water  is  introduced  into  the  bore  and  the 
body  is  rotated  on  its  axis.  By  this  rotary  movement,  the  rein- 
force, while  hanging  loosely  on  the  body,  is  pi’evented  from 
remaining  in  contact  with  it  at  any  one  point,  and  so  prevented 
from  cooling  first  at  this , point.  By  the  introduction  of  the 
water  which  likewise  passes  out  at  the  muzzle,  the  heat,  imparted 
to  the  body  by  the  reinforce,  is  carried  off,  and  the  body  is  pre- 
vented from  being  materially  expanded,  and  so  lessening  the 
pinch  or  force  with  which  the  reinforce  finally  binds  ujion  it. 

643.  As  soon  as  the  reinforce  is  found  to  bind  npon  the 
body,  it  is  covered  with  sand  or  some  other  non-conductor  of 
heat,  the  flow  of  water  continuing  until  the  gun  is  entirely  cold. 
The  object  of  so  covering  up  the  reinforce  is  to  prevent  the 
outer  jiortion  from  cooling  and  contracting  quicker  than  the  in- 
ner portion,  and  to  cause  the  reinforce  to  bind  more  firmly 
upon  fhe  body.  The  thickness  of  the  reinforce  when  finished 
by  boring  the  interior  and  turning  the  exterior  is  about  equal 
to  from  .4  to  .5  the  calibre  of  the  giin,  and  its  length  sufficient 
to  cover  the  usual  charge  of  powder  extending  a distance  of  one 
calibre  in  rear  of  the  bottom  of  the  bore  and  one  calibre  in 
front  of  the  seat  of  the  charge.  The  principle  of  construction 
is  that  of  Initial  Tension. 

644.  The  Yent  is  bored  perpendicularly,  and  enters  the  bore 
at  the  distance  of  half  a calibre  from  the  bottom  of  the  bore. 
It  is  made  in  a bouching  of  pure  copper  screwed  into  the  gun. 
The  upper  portion  of  the  copper  is  i-eplaced  by  steel  f in.  thick, 
to  obtain  a harder  surface  for  the  blow  of  the  hammer. 


Section  III. — British  Naval  Guns. 

645.  THE  AEMSTROHG  SYSTEM.— To  Sir  William 
Armstrong  is  undoulitedly  due  the  merit  of  employing  wrought- 
iron  coils  shrunk  together  to  form  a gun. 

Ills  main  principles  of  gun  architecture  consist  essentially  : 
640.  First.,  in  arranging  the  fibre  of  the  iron  in  the  several 
parts  of  the  gun  so  as  best  to  resist  the  strain  to  which  they 


208 


NAVAL  ORDNANCE  AND  GUNNERY. 


are  respectively  exposed  ; thus  the  walls  or  sides  of  a gun  are 
composed  of  coils  with  the  tibre  running  round  the  gun,  so  as 
to  enable  the  gun  to  bear  the  transverse  strain  of  the" discharge 
without  bursting;  whilst  the  breech  is  fortified  against  the 
longitudinal  strain  or  tendency  to  blow  the  breech  ofP,  by  a 
solid  forged  breech-piece  with  the  fibre,  running  along  the  gun. 

647.  Secondly^  in  shrinking  the  successive  parts  of  the 
gun  together  so  that  not  only  is  cohesion  throughout  the  mass 
insured,  but  the  tension  may  be  so  regulated  that  the  outer 
coils  shall  contribute  a fair  share  to  the  strength  of  the  gun. 

With  regard  to  the  first  principle,  a gun  may  be  destroved 
either  by  bursting  the  barrel  or  by  blowing  off  the  breech. 
Now  wrought-iron  in  the  direction  of  its  fibre  is  about  twice  as 
strong  as  it  is  in  the  cross-direction ; hence  the  best  way  to  em- 
ploy it  to  resist  the  transverse  strain,  is  to  wrap  it  round  and 
round  the  piece  like  a rope.  This  is  the  foundation  of  the 
Armstrong  Coil  System. 

For  a shnilar  reason  the  best  way  to  resist  the  longitudinal 
strain  is  to  place  the  fibre  lengthways ; so  a breech-piece  was 
made  from  a solid  forging  wuih  the  iibre  in  the  required  direc- 
tion. 

With  regard  to  the  second  principle,  it  has  been  shown  that 
the  strength  of  a gun  is  not  proportional  to  its  thickness,  and 
the  gun  should  be  constructed  so  that  each  part  of  its  mass 
would  do  its  proportion  of  work  at  the  instant  of  firing. 

648.  The  Armstrong  Gun.  — The  Armstrong  System  is  the 
basis  of  the  system  now  in  use  in  Great  Britain,  and  a descrip- 
tion of  the  9-inch,  12-ton  gun  is  given,  as  a type  of  the  Arm- 
strong System,  although  it  is  nearly  obsolete.  It  was  the 
method  of  construction  up  to  April,  1867,  for  all  heavy  eruns. 
(Fig.  102.) 


649.  Number  of  Parts. — The  gun  consists  of  a solid  ended 


BUILT-UP  GUNS. 


209 


steel  barrel,  a forged  breech-piece,  a cascabel,  a B tube,  a trun- 
nion-ring, and  seven  coils  : twelve  separate  parts. 

650.  The  Barrel^  or  A Tvhe. — The  steel  cjdinder,  having 
been  bored  for  a barrel,  and  toughened  in  oil,  is  turned  on  the 
exterior  to  suit  the  interior  of  the  breech-piece. 

651.  The  Breech-piece  is  built  by  a series  of  wrought-iron 
slabs  being  successively  molded  together,  and  then  drawn  out, 
bored,  and  turned.  The  breech-piece  will  not  fit  on  the  steel 
tube  when  both  are  cold,  the  difference  in  size  being  the  de- 
signed shrinkage.  The  breech-piece  must  then  be  expanded 
by  heat  until  it  is  sufficiently  large  to  go  over  the  end  of  the 
steel  tube,  where  it  is  allowed  to  cool  and  shrink. 

652.  Cascabel. — The  screw  is  then  cut  for  the  cascabel  in  the 
breech-piece,  the  end  of  the  screw  fitting  evenly  against  the  end 
of  the  barrel.  The  cascabel  is  a solid  forging  of  wrought-iron. 

653.  Shrinking  on  the  Coils. — The  mass  is  now  turned 
down  for  the  B coil,  which  is  shrunk  on.  The  coils  are  heated 
over  a wood-fire  and  placed  in  position  as  soon  as  they  are  suffi- 
ciently expanded,  jets  of  water  being  turned  on  to  assist  in 
shrinking  them.  The  B tube  is  then  shrunk  on,  and  so  on,  coil 
by-coil,  until  the  whole  gun  is  shrunk  up. 

65d.  Coils  and  Tubes. — To  make  a coil,  a bar  is 
taken  of  the  shape  shown  in  the  figure  (103),  heated, 
and  drawn,  while  hot,  upon  a revolving  mandrel  and 
coiled  into  a close  spiral  of  any  required  diameter, 
the  narrower  side  of  the  bar  being  placed  next  to  Fig.  i03. 
the  mandrel ; in  winding,  the  section  of  the  bar  is 

changed  to  rectangular.  The  spiral  is 
heated,  placed  on  end  under  a hammer, 
and  upset  into  a hoop  (Fig.  104),  the 
sides  of  all  the  adjacent  coils  being  thus 
welded  together.  The  hoop  is  also 
patted  on  the  outside  to  preserve  its  cylin- 
drical form.  The  rear  coils  are  flanged 
Fig.  104. -Bar  coiled  to  hook  over  the  breech-piece.  Two- 
make  a hoop.  coils  or  hoops  form  the  B tube  ; one  of 

these  is  turned  down  at  one  end  form- 
ing a shoulder  half  an  inch  long,  and 
the  other  has  a corresponding  recess  (Fig. 

105).  This  last,  having  been 
expanded  by  heat,  is  fitted 
to  the  other,  and  the  recess 
contracts  on  to  the  shoulder 
Fig.  106.— Sec-  (Fig.  106).  They  are  then 
tion  of  weld,  heated,  slipped  over  a loose 
14 


Fig.  105. — Hoop  re- 
cessed to  fit  others.. 


210 


NAVAL  ORDNANCE  AND  GUNNERY. 


mandrel,  and  hammered  to  perfect  the  weld,  thus  forming  the 
B tube. 

655.  The  Trunnion-ring  is  made  of  slabs  of  iron  consec- 
utively welded  together  on  the  flattened  end  of  a porter-har^ 
and  gradually  formed  into  a ring  by  slitting  the  pile  with  a 
small  iron  wedge,  and  then  with  a series  of  taper  mandrelr. 
The  trunnions  are  hammered  at  the  same  time  out  of  the 
ends  of  the  pile.  It  is  then  cut  off  from  the  end  of  the  porter- 
bar,  the  ring  bored  and  slightly  recessed  to  fit  a corresponding 
projection  on  the  coil  beneath  it,  and  is  slipped  over  when 
sufiiciently  expanded  by  heat. 

656.  THE  FRAZER  SYSTEM. — Mr.  Frazers  plan  is  an 
important  modiflcation  of  Armstrong’s,  from  which  it  differs 
principally  in  building  up  a gun  of  a few  long  double  and  triple 
coils,  instead  of  several  short  single  ones,  and  a forged  breech- 
piece.  (Fig.  107.) 


657.  Great  expense  is  saved  by  this  means,  as  there  is  much 
less  surface  to  be  bored  and  turned.  IVith  respect  to  theory, 
it  may  be  urged  in  its  favor,  in  the  first  place,  that  a forged 
breech-piece  (which  is  comparatively  expensive  and  liable  to 
fly  into  fragments,  should  the  gun  hurst)  is  not  required  with  a 
solid  ended  steel-barrel  and  long  thick  coils,  although  it  is 
necessary  with  several  short  coils  to  compensate  for  the  longi- 
tudinal weakness  of  their  joints.  The  whole  of  the  wrought- 
iron,  therefore,  can  be  coiled  round  the  barrel,  and  thus  give 
extra  transverse  strength.  Again,  the  trunnion-ring,  which 
was  shrunk  on  in  the  original  construction,  is  welded  on  to  the 
breech  coil  in  the  Frazer  plan,  so  that  there  is  no  fear  of  slipping. 

658.  IVith  regard  to  the  second  Armstrong  principle, 
although  a series  of  thin  coils  helps  us  to  distribute  the  in- 
duced strain  upon  a gun  by  shrinking  on  each  coil  separately, 
the  method  is  open  to  the  serious  objection,  that  it  is  practi- 
cally difliciilt  to  calculate  the  respective  proportionate  amount 
of  extension,  and,  consequently,  the  greater  the  number  of 
pieces  in  a gun,  the  more  likely  that  some  weakness  will  exist 
in  the  mass  owing  to  the  undue  strain  on  some  of  its  parts. 


BUILT-UP  GUNS. 


211 


659.  Shrinking  on  tiie  coils  successively  was  adopted  by 
Sir  lyilliam  Armstrong,  as  a convenient  mode  of  adhesion, 
and  not  on  the  distribution  theory.  In  the  formation  of  a 
triple  coil,  it  is  generally  a manufacturing  necessity  to  have 
the  first  coil  cold  before  the  second  bar  is  wound  round ; but 
the  third  bar  is  wound  on  while  the  second  coil  is  hot ; the  sec- 
ond and  third  layers,  therefore,  contract  nearly  simultaneously, 
and  are  kept  in  a state  of  tension,  by  the  first  which  they  com- 
press to  a certain  degree,  thus  carrying  out  the  theory  of  Initial 
Tension. 

660.  But  the  grand  decisive  fact  bearing  upon  this  question, 
was  the  favorable  result  of  the  trials  for  comparative  endur- 
ance, which  the  64-pounder  and  9-inch  s|>ecimen  guns  under- 
went, and  in  virtue  of  which  the  Frazer  system  superseded  the 
original  single  coil  system  of  Armstrong,  towards  the  close  of 
1866. 

661.  THE  "WOOLWICH  GUH. — The  name  “ Woolwich 
Gun  ” is  the  term  applied  to  all  the  guns  manufactured  in  England 
since  1866.  The  term  is  a comprehensive  one,  and  might  be 
expanded  into  “ Wrought-iron-muzzle-loading-guns,  built  on 
Sir  William  Armstrong’s  principle,  modified  by  Mr.  Frazer, 
improved  by  Mr.  Anderson’s  method  of  hooking  the  coils 
with  solid-ended  steel  tubes  toughened  in  oil,  rifled  on  the 
French  system,  modified  as  recommended  by  the  Ordnance 
Select  Committee,  for  projectiles  studded  according  to  Major 
Palliser’s  plan.” 

662.  Details  of  the  Gun. — The  gun  consists  of : 

(1.)  An  A tube. 

(2.)  A B tube. 

(3.)  A breech-coil. 

(4:.)  A cascabel. 


663.  (1.)  The  A tube,  or  inner  barrel  (Fig.  109),  is  made 
from  a solid  forged  cylinder  of  cast-steel,  which  is  supplied  to 
the  Royal  Gun  Factory  bjr  Messrs.  Firth,  of  Shefiield.  Cast- 
ing is  necessary,  not  only  for  the  purpose  of  obtaining  a suffi- 
ciently large  block  of  steel,  but  also  of  making  the  block  homo- 


212 


NAVAL  ORDNANCE  AND  GUNNERY. 


Fig.  109. 


geneoiis  and  uniform  in  density.  Forging  imparts  to  it  tlie 
properties  of  great  solidity  and  density. 

A piece  is  cut  from 
the  block  at  the  breech 
end,  and  divided  into 
small  pieces  which  are 
tested  for  tensile 
strength  and  elasticity 
in  the  natural  state, 
and  also  to  ascertain  at 
what  temperature  the 
block  can  be  immersed 
in  oil  to  the  best  ad- 
vantage. 

A steel-block  which  stands  all  the  tests,  is  rough-turned,  in 
which  operation  a lip  is  foianed  on  the  muzzle  to  farilitate  lift- 
ing the  tube  into  or  out  of  the  furnace  or  oil-bath.  It  is  then 
bored  roughly  from  the  solid. 

The  tube  thus  formed  is  heated  from  four  to  six  hours  to 
the  approved  temperature  in  a vertical  furnace,  and  then 
plunged  into  an  adjacent  bath  of  oil,  in  which  it  is  allowed  to 
cool  and  soak,  generally  twelve  hours.  It  must  then  be  turned 
and  bored  to  make  it  straight  inside  and  outside,  and  to  re- 
move any  flaws. 

It  is  then  subjected  to  the  water-test  of  8,000  pounds  per 
square  inch,  and,  if  no  flaw  is  detected,  the  barrel  is  considered 
safe,  and  remains  in  this  condition  until  the  B tube  is  ready  to 
be  shrunk  over  it. 

CGI.  (2.)  The  B tube  is 
composed  of  two  single  and 
slightly  taper  coils  united 
together  (Fig.  110).  The 
two  coils,  being  made  and 
welded  in  the  usual  man- 
ner, are  faced  and  recipro- 
cally recessed  to  the  depth 
of  about  one  inch,  and  then 

united  together  endways  by  expanding  the  recess  of  a 
heat,  and  allowing  it  to  shrink 
the  shoulder  of  the  other  (Fi 


coil  by 
around 
111). 


This  holds  the  two  coils  together 
enough  to  allow  the  tube  thus  formed, 
to  be  placed  upright  in  a furnace  ; when 
it  arrives  at  welding-heat,  it  is  removed 
to  a steam-hammer,  and  receives  on  its  end  six  or  seven  blows, 


Fig.  110. 


Fig.  111. 


BUILT-UP  GUNS. 


213 


Fig.  112. 


wliicli  weld  tlie  joint  completely.  The  tube  is  next  rough- 
turned,  in  which  process  a rim  is  left  near  the  muzzle  for  con- 
venience in  lifting,  and  then  rough  and  fine  bored  (Fig.  112). 
The  interior  of  the  B tube  having  been 
brought  to  the  required  smoothness  for 
contact  with  the  steel  barrel,  it  is  gauged 
every  twelve  inches  down  the  bore,  and  at 
the  shoulder. 

To  the  measurement  the  calculated 
amount  of  shrinkage  is  added,  and  the  exterior  of  the  A tube 
is  turned  so  that  it  shall  be  exactly  larger  than  the  interior  of 
the  B tube  by  the  recpiired  amount  of  shrinkage. 

665.  (3.)  The  Breech-coil  is  composed  of  a triple-coil,  a 
douUe-coil,  and  a trunnion-ring.  The  triple-coil  (Fig.  IIS')  is 
made  of  three  bars,  all  of  the  same 
section,  but  diliering,  of  course,  in 
length ; the  middle  one  is  coiled  in 
a reverse  direction  so  as  to  break 
joints.  To  weld  the  folds,  it  is 
raised  to  welding-heat  in  a furnace, 
and  hammered  on  end  ; then  a man- 
drel is  forced  down  inside  from  either 
end,  and  it  is  hammered  on  the  out- 
side, being  heated  before  each  opera- 
tion. When  cold,  the  ends  are  faced, 
and  the  outer  coil  is  turned  down  at 
the  muzzle  end  to  form  a shoulder 
for  the  reception  of  the  trunnion-  fig.  113. 

ring. 

The  double  coil  (Fig.  114)  is  made  of  two  bars  of  the 
same  section  as  those  of  the  triple  coil,  but  of  dilferent  lengths. 
It  is  made  in  the  same  manner  as  the  triple  coil,  and  it  has  a 
shoulder  formed  at  its 
lower  end,  so  that  it 
may  overlap  the  trun- 
nion-ring. 

The  trunnion-ring 
(Fig.  115)  is  made  like 
all  wrought-iron  trun- 
nion-rings, being  built 
up  on  the  end  of  a porter-bar. 

All  these  parts,  triple-coil,  double-coil, 
and  trunnion-ring,  being  thus  prepared, 
the  trunnion-ring  is  heated  to  redness 
and  dropped  on  the  shoulder  of  the  triple- 


Fig.  114. 


214 


NAVAL  ORDNANCE  AND  GUNNERY. 


Fig.  116. 


coil,  whicli  is  placed  upright  on  its  breecli  end  for  this  pni-pose  ; 
while  the  trunnion-ring  is  still  hot,  the  douhle-coil  is  dropped 
down  on  the  front  of  the  triple-coil  through  the  upper  portion 
of  the  trunnion-ring,  which  thus  forms  a band  over  the  joint, 

and  in  cooling  grips  the  two 
coils  (Fig.  116)  sufficiently  to 
admit  of  the  whole  mass  being 
placed  bodily  in  the  furnace, 
where  it  is  raised  to  welding- 
heat.  It  is  then  placed  on  its 
breech  end  under  a heavy  ham- 
mer ; six  or  seven  blows  suffice 
to  amalgamate  all  the  parts;  hut 
to  make  the  weld  more  perfect 
in  the  interior,  a_cast-iron  man- 
drel is  forced  down  the  bore  to  within  20  inches  of  the  breech. 
The  mass  is  then  reversed,  and  the  mandrel  driven  out 
again.  It  is  then  turned  and  bored.  The  front  of  the  d.ouble 
coil  is  recessed  to  a distance  of  nine  inches,  and  deep  enough  to 

overlap  the  B tube.  Finally  the 
thread  is  cut  for  the  cascabel. 
(Fig.  117.) 

6G6.  (4.)  The  eascaljel  is  made 
of  the  best  scrap-iron.  It  is  first 
forged  into  a single  cylinder, 
then  turned,  and  a bevel  thread 
cut  on  it.  A hole  which  is  after- 
ward enlarged  to  a loop  is  drilled 
through  the  end.  (Fig.  IIS.) 

One  round  of  the  thread  is 
turned  off  at  the  end  of  the  cas- 
cabel,  so  that  there  may  be  an 
annular  space  there,  which,  in 
connection  with  the  channel  now 
cut  along  the  cascabel  and  across 
the  threads  inch  in  depth, 
forms  the  gas-escape  which  comes  out  at  the  right  side  of  the 

loop.  This  will  give  notice,  in  ease 
FORGED  SCREWED  ^hc  stecl  tiibe  should  split. 

667.  Buildeng  up  the  Gun. — The 
A tube  and  the  B tube,  being  pi’e- 
pared  as  described,  are  shrunk  together 
in  the  following  manner  : the  B tube 
is  placed  over  a grating,  and  heated  for  about  two  hours  by  a 
wood-fire,  for  which  the  tube  itself  forms  the  flue,  until  it  is 


Fig.  118. 


BUILT-UP  GUNS. 


215 


Fig.  119. 


sufficiently  expanded  to  drop  easily  over  tlie  muzzle-end  of 
the  A tube,  which  is  placed  upright  in  a pit  ready  to  receive 
it.  The  B tube  is  then  raised,  the  ashes  brushed  from  its  in- 
terior, and  it  is 
dropped  over  the 
steel  barrel  (Fig.  119). 

During  the  process  of 
shrinking,  a stream  of 
cold  water  is  poured 
into  the  ' steel  barrel 
by  means  of  a pipe  and  sj^ihon — to  keep  it  as  cool  as  possible. 
A ring  of  gas  is  placed  at  the  muzzle-end  of  the  B tube  to  pre- 
vent its  coohug  prematurely,  and  jets  of  cold  water  play  on  the 
other  end,  and  are  gradually  raised  to  the  muzzle  for  the  pur- 
pose of  cooling  the  whole  tube  consecutively  from  the  breech 
end,  which  it  is  desirable  should  grip  first.  The  method  of 
cooling  the  tube  prevents  it  from  being  drawn  out  into  a state 
of  longitudinal  tension. 

The  A and  B tubes,  shrunk  up,  are  placed  in  a lathe,  and 
while  one  cutter  fine-turns  the  B tube  to  its  proper  shape,  an- 
other cutter  fine-turns  the  breech  end  of  the  A tube  according 
to  the  plan  of  the  breech-coil. 

The  half-formed  gun,  composed  of  the  A and  B tubes,  is 
placed  on  its  muzzle  in  the  shrinking-pit,  and  the  breech-coil 
is  heated  and  shrunk  on  in  the  same  manner  as  the  B tube  ; 
it  is,  however,  being  nearly  of  the  same  thickness  throughout, 
allowed  to  cool  naturally,  and  cold  water  is  forced  up  into  the 
bore  of  the  gun  by  a jet  round  which  the  muzzle  rests. 

The  cascabel  is  next  screwed  in,  which  operation  requires 
great  care,  as  the  front  of  it  must  bear  evenly  against  the  steel 
barrel.  After  it  is  screwed  in,  it  is  splined  to  prevent  it  from 
turning. 

668.  The  above  method  of  construction  is  now  applied  to 


Fig.  120. 

the  7-inch  and  8-inch  guns  (Fig.  120).  It  has  been  modified 


216 


NAVAL  ORDNANCE  AND  GUNNERY. 


for  the  9-inch  guns  (Fig.  121),  and  upwards,  hy  using  a slightly 
thinner  steel  tube  and  two  double  coils  on  the  breech  instead  of 
one  tri])le  coil. 


Fig.  121. 


The  higher  natures  have  an  intermediate  B noil  in  addition 
(Fig.  122),\nd  the  12-inch  35-ton  gun  has  a button  instead  of 
a cascabel  hole. 


r—1—; 


669.  Yent. — The  vent  enters  at  a point  two-fifths  the 
length  of  the  seiwice-cartridge  from  the  end.  The  vents  are 
lined  with  copper,  specially  hardened,  and  bored  vertically  in 
the  7-inch,  8-inch,  and  9-inch  guns;  but  in  the  10-inch  and  12- 
iiicli  gnus  they  are  bored  at  an  angle  of  45°  with  the  vertical, 
and  on  the  right  side  of  a broadside  gun,  but  on  the  most  con- 
venient side  in  a turret-gun. 

670.  Nomenclature. — The  guns  are  named  as  follows  : 


The  12-inch 

12-inch 

10-inch 

400-pdr. 

9-inch 

12-ton 

S-inch 

......  ISO-pdr. 

7-inch 

115-pdr. 

BUrLT-HP  GTJXS. 


217 


671.  PALLISEE  SYSTEM  OE  COEYERSIO]Y.— This 
system  of  Major  Palliser  depends  on  the  principle  of  Yarying 
Elasticity,  and  recourse  has  been  had  to  it  in  order  to  utilize 
the  smooth-bore  cast-iron  guns.  Some  smooth-bore  6d-pdrs. 
are  the  only  ones  which  have  been  converted. 

672.  Tlieorxj  of  the  System. — A barrel  or  hollow  cylinder 
of  coiled  wrought-u’on  is  introduced  into  a cast-iron  gun,  the 
barrel  being  of  such  thickness  in  proportion  to  its  calibre  that 
the  residual  strain  borne  by  this  tube  shall  bear  a relation  to 
the  strain  it  transmits  to  the  surrounding  cast-iron  which  shall 
be  best  proportioned  to  their  respective  elasticities.  The  pre- 
cise proportions  will  depend  on  various  circumstances,  the  prin- 
cipal of  which  are  the  excessive  expansion  of  wrought-iron  due 
to  heat,  and  great  range  between  the  limits  of  elasticity  and 
rupture. 

The  cast-iron  will  have  to  do  nearly  all  the  longitudinal 
work.  By  varying  the  thickness  of  the  tube,  the  transmitted 
strains  can  be  regulated  to  the  greatest  nicety. 

673.  Method  of  Gonsteuctiox. — The  gim  having  been 
bored,  a coiled  wrought-iron  tube  is  inserted  (Fig.  123).  The 


tube  consists  of  two  thin  wrought-iron  ban-els,  the  outer  one 
being  much  shorter  than  the  inner  one,  and  shrunk  to  it  at  the 
breech  end.  Two  are  used  for  the  pui-pose  of  obtaining  the 
benefit  of  the  tension,  and  also  to  break  the  continuity  of  any 
internal  fracture.  The  end  of  the  tube  is  closed  by  a solid 
wrought-iron  breech-screw.  The  tube  is  made  slightly  taper, 
and  the  bore  of  the  gun  is  tapered  correspondingly ; the  tube  is 
placed  in  the  bore,  and  as  soon  as  it  comes  in  contact  through- 
out its  length,  a screw-locking-ring  A,  which  takes  against  a 
shoulder  on  the  tube,  is  screwed  into  the  muzzle,  and  sets  the 
tube  home ; and  since  in  practice  it  has  been  found  that  the 
elasticity  of  the  wrought-iron  inner  tube  is  not  proportioned  to 
its  greater  elongation,  the  deficiency  is  supplied  by  putting  the 
tube  under  a slight  compression,  which  is  effected  by  perma- 
nently stretching  the  wrought -u’on  in  the  gun  by  heavy  proof- 


218 


NAVAL  ORDNANCE  AND  GUNNERY. 


charges.  The  tube  is  further  secured  in  the  gun  by  means  of 
a screw  which  passes  through  the  cast-iron  shell  a short  distance 
before  the  trunnions  at  right-angles  to  the  bore,  and  screws 
into  the  tube. 

674.  PAKSOdd’S  SYSTEM  OF  CONYEESIOX.— Mr. 
Parsons  has  proposed  that  the  tube  should  be  made  of  steel, 
having  a solid  breech,  A (Fig.  124),  the  ingot  not  being  bored 


through  its  entire  length.  He  proposes  to  reinforce  the  tube 
M'ith  jackets  of  steel  shrunk  on,  B,  and  to  insert  the  whole, 
tube  and  jacket,  from  the  rear  of  the  iron  casting,  the  cast-iron 
gun  being  so  bored  out  as  to  recpiire  force  to  insert  the  tube  in 
its  place.  The  tube  being  inserted,  a steel  plug,  C,  is  to  be 
screwed  in  from  the  rear,  which  presses  against  the  rear  of  the 
tube,  and  the  breech  is  then  closed  by  a cast-iron  plug  repre- 
senting the  cascabel  of  the  piece,  I). 

Various  projects  have  been  brought  forward  to  convert  our 
present  smootii-bore  guns  into  rifles,  but  these  are  all  make- 
shifts. All  of  our  smooth-bore  guns  are  of  too  high  a calibre, 
I’elative  to  their  length  of  bore  and  weight,  to  be  usefvdly  con- 
verted. 

675.  EXPEPIMENTAL  GUXS. — TheMhitwoeth  Gux 
is  made  of  a substance  called  compressed  steely  which  is  said  to 
be  obtained  by  melting  short  bars  of  Swedish  iron  with  a small 
quantity  of  carbonaceous  matter  in  crucibles,  after  which  it  is 
cast  into  round  ingots  and  compressed  by  hydraulic  presses 
while  fluid.  The  smaller  Whitworth  guns  are  forged  solid; 
the  larger  ones  are  built  up  with  hoops  (Fig.  125).  The  barrel 
is  made  by  casting  an  ingot  hollow.  A taper  mandrel  is 
inserted  in  the  hole,  and  the  whole  tube  is  hammered  until  it  is 
of  the  desired  size  and  shape.  The  hoops  are  flrst  cast  hollow, 
and  then  hammered  over  a steel  mandrel  or  rolled  in  a revolv- 
ing-machine. Before  receiving  their  flnal  finish  they  are  an- 
nealed. The  hoops  are  screwed  together  to  form  a tube,  and 


BUILT-UP  GUNS. 


219 


the  tubes  are  bored  with  a slight  taper  and  forced  on  over  each 
other  by  hydraulic  presses,  in  order  to  secure  initial  tensiou. 
In  the  larger  guns  the  breech  is  hooped  with  a harder  and  a 


higher  steel  than  the  barrel.  The  breech-plug  is  made  with 
offsets  in  such  a way  as  to  screw  into  the  barrel  and  the  two 
adjoining  hoops. 

676.  The  Blakely  Gun. — The  most  approved  pattern  of 
the  Blakely  Gun  combines  in  its  construction  the  principles  of 
Initial  Tension  and  Varying  Elasticity,  in  order  to  call  all  the 
metal  of  the  piece  into  simultaneous  play  (Fig.  126).  The 


inner  tube  is  made  of  low  steel  having  considerable  elasticity, 
but  not  quite  enough.  The  next  tube  is  made  of  high  steel 
with  less  elasticity,  and  is  shrunk  on  to  the  inner  tube  with 
just  sufficient  tension  to  compensate  for  the  want  of  elasticity. 
It  is  hooked  at  the  breech  end  over  the  inner  tube.  The  outer 
cast-iron  jacket,  to  which  the  trunnions  are  attached,  is  the  least 
elastic  of  all,  and  is  put  on  only  with  the  shrinkage  obtained 
by  warming  it  over  a lire.  It  is  hooked  over  the  tube  within. 
The  steel  tubes  are  cast  hollow  and  hammered  over  steel  man- 
drels, by  which  the  tenacity  of  the  metal  is  much  increased. 
All  the  steel  parts  are  annealed. 


220 


NAVAL  ORDNANCE  AND  GUNNERY. 


677.  The  Yavasseur  Systeji  consists  of  a steel  tube  with 
hoops  of  the  same  material.  The  strength  is  cast  more  upon 
the  hoops  and  less  upon  the  tube,  Avhich  is  quite  thin  and 
jacketed  from  the  breech  to  a short  chstance  in  front  of  the 
trunnions,  with  a second  tube  shrunk  upon  it ; the  hoops  en- 
circle the  jacketed  and  unjacketed  parts,  extending  to  the 
muzzle.  (Fig.  127.) 

The  figure  represents  a 7-inch  gun  of  this  make.  It  is  built 
entirely  of  Fiidh  steel,  except  the  trunnion-band,  F,  which  is 


Fig.  137. — ^VavasBeur  7-inch  [steel]. 


made  of  wrought-iron.  The  tube.  A,  the  jackets,  B,  C,  D, 
and  the  breech-plug,  G,  are  of  cast-steel,  the  tube.  A,  being  oil- 
tempered.  The  exterior  rings,  E,  are  forged  and  rolled  like 
railway  tires  (Art.  706).  The  A'ent  is  at  a distance  from  the  bot- 
tom of  the  bore  eqtial  to  two-fifths  length  of  the  cartridge. 


Section  IV. — French  JVavcd  Guns. 


678.  General  Description. — ^Breech-loading,  rifled  cast- 
iron  guns  liooped  with  steel  Avere  introduced  into  the  French 
navy  about  1860.  On  these  being  considered  deficient  in 
poAver,  elforts  to  olitain  increased  strength  AA’ere  made,  which 
resulted,  in  1871,  in  the  adoption  of  the  system  now  in  use. 

679.  Model  of  1871. — The  model  of  1871  comprises  the 
calibres  of  12.18  inches,  9.36  inches,  7.32  inches,  and  5.16 


Fig.  128. 


inches.  They  are  all  cast-iron  breech-loading  guns,  hooped 
and  lined  with  steel. 


BUILT-UP  GLWS. 


221 


680.  Casting. — Second-fusion  gray  cast-iron  is  used  exclu- 
sively in  the  manufacture  of  these  guns.  They  are  cast  in  a 
mold  with  a hollow  core,  and  cooled  from  the  interior.  The 
chase  occupies  the  lower  part  of  the  mold. 

681.  Lining. — The  tubes  to  line  the  bore  are  made  of  Bessemer 
steel,  forged  and  tempered  in  oil,  furnished  by  Messrs.  Petin  & 
Gaudet.  The  tube  is  introduced  into  the  gun  from  the  rear  or 
breech  end,  and  has  welded  on  its  after-end  a collar  having  a 
thread  on  the  outside  which  screws  into  the  metal  of  the  gun ; 
on  the  inside  of  the  collar  is  the  thread  for  the  breech-screw. 

The  tube  is  introduced  into  a lodgment  about  .007  inches 
less  in  diameter  than  the  exterior  diameter  of  the  tube ; the 
length  of  the  lodgment  is  also  about  .007  inches  less  than  that 
of  the  tube. 

682.  To  insert  the  tube,  that  part  of  the  gun  which  is  to 
contain  it,  is  raised  to  a certain  heat  which  will  insure  the  right 
amount  of  expansion.  The  tube  is  inserted  cold  and  screwed 
up,  and  the  cast-iron  in  cooling  compresses  it,  both  longitudinally 
and  transversely.  The  greatest  objection  is  the  difficulty  of 
making  the  joint  tight.  Tubes  extending  the  whole  length  of 
the  gnu  have  been  used,  but  without  such  good  results. 

683.  The  Hoops. — The  hoops  are  rings  of  puddled  steel, 
very  strong  and  elastic  ; mild  steel,  homogeneous,  with  a regu- 
lar libre,  is  generally  chosen.  The  body  of  the  gun  is  turned 
perfectly  cylindrical,  and  of  a diameter  slightly  greater  than 
the  interior  diameter  of  the  hoops ; they  are  then  heated  and 
shrunk  on,  and  the  gun  is  cooled  interiorly  by  running  water 
through  the  bore. 

68d.  The  gun  is  cast  without  trunnions,  and  they  are  built 
upon  one  of  the  hoops,  which  is  called  the  trunnion-hoop.  The 
larger  calibres  have  a double  row  of  hoops  breaking  joints. 

685.  Gxis-CHECK. — The  Broadmell  Ming  forms  the  gas- 
check  for  these  guns.  This  is  the  invention  of  Mr.  Broadwell, 
an  American,  and  it  is  adopted  generally  as  the  gas-check  in 
all  successful  breech-loading  systems. 

686.  The  Broadwell  Ring  is  an  arrangement  illustrated 
by  Pig.  129.  It  consists  of  a curved  ring,  I,  and  flat  bearing- 
plate,  II.  The  curved  ring  is  fitted  in  a correspondingly 
shaped  chamber,  and  like  a steam-valve,  for  instance,  may  be 
made  perfectly  gas-tight,  independently  of  the  expansive  force 
of  the  gas,  by  being  pressed  tightly  into  the  chamber  by  the 
breech-closing  apparatus. 

The  curved  self-adjusting  gas-ring  and  adjustable  bearing- 
plate  are  exceedingly  simple, — the  ring  completely  filling  the 
chamber,  and  being  free  to  move  in  any  direction  that  may  be 


222 


NAVAL  ORDNANCE  AND  GLTNNERY. 


necessary  in  order  to  bear  accurately  upon  the  plate,  witbout 
in  the  least  impairing  its  mechanical  ht  in  its  chamber. 


Fig.  129. 


687.  The  French  Gum  of  old  model  had  the  gas-check 
fixed  to  the  axis  of  the  breech-plug,  but  this  led  to  difiiculties 
of  Avorldng,  particularly  when  using  very  quick  powder,  and 
when  the  initial  velocities  became  considerable.  Tliese  guns 
had  two  lodgments  for  the  gas-check,  the  one  nearest^  the 
breech  being  reserved  for  the  time  when  degradations  of  the 
bore  at  the  other,  had  occurred  sufiiciently  to  prevent  a com- 
plete closure. 

This  change  was  very  efficacious  in  prolonging  the  life  of  the 
piece,  and  only  required  a shorter  axis  for  the  new  gas-check. 

688.  In  the  model  of  1871,  only  one  lodgement  is  made  in 
the  gun  ; the  gas-check,  DE  (Fig.  130),  is  of  the  same  shape,  but 
is  i^iaced  by  hand  in  the  lodgement,  and  driven  up  by  the 
breech-screw,  S.  It  remains  in  place  throughout  the  tirina’. 
The  central  opening  is.made  of  the  same  diameter  as  the  pow- 
der-chamber, and  the  side  is  strengthened  b}’'  a projection.  It 
freely  admits  the  passage  of  the  ammunition.  In  the  larae 
guns  the  gas-checks  are  made  of  copper,  and  in  the  small  ou"es 
of  steel.  If  destroyed,  they  are  easily  renewed. 

689.  Beeecii-sceew. — The  breech  is  closed  with  a screw- 
plug  of  cast-steel,  having  fourteen  threads,  which  is  screwed 
into  the  rear  part  of  the  bore. 

Were  it  necessary  in  firing  to  screw  and  unscrew  the  whole 
length  of  this  plug  at  every  round,  much  time  would  be 


BUILT-UP  GUNS. 


223 


wasted ; but  tliis  is  obviated  by  dividing  the  screw  into  six 
parts,  in  the  direction  of  its  axis,  the  threads  being  removed 


Fig.  130. 


from  every  other  one,  both  from  the  ping  and  from  the  breech 
of  the  gnn.  When  the  breec-h  is  to  be  closed,  the  threaded 
portions  of  the  ping  are  presented  so  that  they  come  opposite 
the  smooth  parts  of  the  breech-hole.  The  plug  is  then  pushed 
in,  when  a sixth  of  a turn  with  a handle  brings  the  screw  of 
both  parts  together.  (Fig.  132.) 

690.  This  system  of  closing  the  breech  by  means  of  a 
slotted  screw,  or  one  having  interrupted  threads,  was  first  pro- 
posed by  an  American  named  Eastman,  and  has  been  adopted 
by  the  French  with  excellent  results. 

691.  In  the  model  of  1871  the  threads  are  inclmed  so  that 
the  plug  will  be  better  supported  from  the  rear.  (Fig.  130.) 
There  is  a slight  hollow  in  the  front  end  of  the  plug  opposite 
the  central  opening  of  the  gas-check.  To  make  the  closm-e 
still  more  complete,  a cop]jer  ring,  AB,  projecting  .01  inches,  is 
sunk  into  the  front  end  of  the  plug.  This  ring,  on  which  the 
bottom  of  the  gas-check  rests,  oilers  a surface  of  softer  metal, 
and  assists  in  making  the  contact  more  perfect. 

692.  The  ring,  as  well  as  the  base  of  the  gas-cheek,  has 
three  concentric  grooves,  .05  inches  wide  and  deep,  which  fur- 
nish lodgements  for  any  gas  that  may  escape,  and  prevent  it  from 


224 


NAVAL  ORDNANCE  AND  GUNNERY. 


reacliing  tlie  metal  of  the  gun.  To  reserve  a place  of  deposit 
for  the  residuum  from  the  bore,  the  part,  AC,  between  the 
lodgement  of  the  gas-cheek  and  the  threads  of  the  collar,  is 
bored  out  to  the  same  diameter  as  the  bottom  of  the  thi-eads. 

693.  To  close  the  Breech. — A strong  cranked  lever  serves  to 

manipulate  the  hreech-plug,  by 
turning  which  the  threads  of  the 
screw  enter  the  corresponding 
grooves.  The  movement  in  the 
contrary  direction  disengages 
them. 

694.  The  breech  being  closed, 
the  lever-handle  is  prevented 
from  moving  back,  and  thus  al- 
lowing the  plug  to  he  unscrewed 
by  a short  metal  catch,  a (Fig. 
131),  working  freely  on  a stud 
placed  in  the  upper  part  of  the 
right  side  of  the  breech.  This 
catch  lifts  as  the  lever-handle 
reaches  it,  and  allows  it  to  pass, 
hut  drops  by  the  action  of  a spring  when  the  handle  has 
passed,  and  thus  prevents  the  lever  from  moving  to  the  left,  a 
stud  on  the  breach  prevents  it  from  moving  to  the  right. 

695.  To  open  the  Breech. — The  weight  of  the  breech-plug  for 
a 9-|-inch  gun  is  about  500  pounds ; therefore  a support,  or  col- 
lar, is  used  to  hold  it,  when  withdrawn.  This  is  a metallic 
frame  carrying  a bracket,  A (Fig.  132),  hinged  to  the  side  of 

the  breech  near  the  open- 
ing. It  has  a kind  of  gut- 
ter in  which  slides  the 
screw  portion  of  the  plug. 
This  support  being  placed 
in  a line  with  the  bore,  the 
hand  gripe  at  the  mid- 
dle of  the  breech-plug  is 
seized,  and  the  screw  being 
disengaged,  a strong  pull 
will  bring  the  whole  to  the 
rear.  The  impulse  given 
swings  it  open,  the  breech- 
screw  remaining  fixed  in 
its  support,  or  collar.  A 
safety-catch  held  by  a 

spring  secures  the  collar  fair  in  a line  with  the  bore. 


BUILT-UP  GXmS. 


225 


696.  Loading. — The  breech-plug  being  swung  round  at 
right  angles  to  the  bore  on  its  support,  an  iron  bearer  is  intro- 
duced to  facilitate  the  loading  of  the  projectile,  and  prevent 
the  cartridge  from  being  torn  by  the  threads  of  the  screwn  It 
is  kept  in  position  by  a lever  and  stud  fixed  to  the  under  side 
of  the  breech.  The  bearer  has  a groove  to  guide  the  projectile, 
and  it  is  long  enough  to  clear  the  tapped  portion  of  the  breech. 
It  is  readily  moved  in  and  out  by  hand.  The  projectile  is 
placed  on  this  bearer  and  pushed  into  the  bore ; a Avad  of  dried 
sea-Aveed  is  then  pushed  in,  and  aftenvards  the  cartridge  ; the 
plug  is  then  pushed  in,  and  sci’ewed  up. 

697.  Safety-catch. — To  obviate  the  danger  resulting  from  a 
neglect  to  screw  up  the  plug  when  the  breech  is  closed,  the 
lock-lanyard,  which  has  a bob  on  it,  is  made  to  pass  through 
the  eye,  c (Fig.  131),  of  a piece  of  iron  fixed  to  the  breech. 
When  the  handle  is  not  in  its  place,  that  is,  wdien  the  plug  is 
not  properly  screwed  in,  a spring,  5,  closes  the  eye  and  does  not 
allow  the  bob  to  pass.  When  the  handle  is  in  position  with 
the  plug  screwed  up,  it  opens  the  eye  and  allows  the  bob  to 
pass,  Avheii  the  gun  can  be  fired. 

698.  The  linFEVE  Gux. — This  is  a small  bronze  breech- 
loader, introduced  during  the  war  of  1870  by  Col.  De  Kefiye. 
Its  distinctive  feature  seems  to  be  its  metallic  cartridge,  which 
is  interesting  because  it  is  proposed  to  introduce  in  our  service  a 
breech-loading  3-inch  rifled  howitzer  using  a metallic  cartridge- 
case. 

699.  The  Iteffye  Cartridge. — This  is  composed  of  com- 
pressed powder  enclosed  in  a metallic  case.  The  rigidity  of 
the  cartridge-ease  offers  the  valuable  adA’antage  of  permitting 
the  employment  of  powder  pressed  in  cakes,  which  preserve 
that  form  and  condition  calculated  to  produce  the  best  effect 
from  the  expanding  gases.  Besides,  the  ease  furnishes  a lining 
to  the  chamber,  and  also  serA'es  as  a gas-check.  (Fig.  133.) 

The  cartridge  cylinder  is  made  from  a sheet  of  tin,  rolled 
on  a mandrel  and  covered  with  seAmral  layers  of  paper  rolled 
on,  using  glue  betAveen  all  surfaces. 

The  head,  AB,  is  a brass  cup  contracted  at  the  open  end 
and  slightly  enlarged  at  the  bottom.  A depression  is  formed 
in  its  base,  called  the  yjriming-charriber,  which  also  serves  as  a 
compartment  for  the  vent  gas-check  arrangement,  CD.  A hole 
is  drilled  in  the  centre  of  this  indentation,  E,  for  the  rivet  of 
the  gas-check,  and  the  sides  are  pierced  at  the  point  where  the 
bottom  joins- with  six  holes,  hh,  to  permit  the  passage  of  the 
flame  to  the  charge.  A brass  disk  or  gas-check,  CD,  is  riveted 
to  the  bottom  of  the  priming-chamber,  and  it  is  chamfered  at 
15 


226 


NAVAL  ORDNANCE  AND  GUNNERY. 


the  edges,  so  as  to  avoid  closing  the  holes  communicating  with 
the  charge.  A brass  cup  fits  snugly  in  the  depression  of  the 
head,  fomfing  a part  of  the  priming-chamber,  and  it  is  pierced 

to  correspond  with  the  axis  of 
the  vent. 

The  wad,  GII,  is  made  by 
rolling  sheets  of  paper  in  cylin- 
ders, which  are  then  cut  up 
into  the  required  sizes.  These 
serve  as  wedges,  binding  the 
tube  and  head  close  together. 

In  making  up  the  case,  the 
lower  edge  of  the  cylinder, 
having  been  slit^with  hand- 
shears,  is  inserted  in  the  head 
and  shoved  down  until  the 
edge  takes  against  the  priming- 
chamber. 

The  cylindrical  paper  wad 
is  now  dropped  in  the  ease, 
just  fitting  over  the  priming- 
chamber,  and  pressed  down 
with  a punch,  which  forces  it 
against  the  sides  and  upon  tlie 
bottom  of  the  bent  tin.  The 
head  is  secured  by  rivets.  Ell, 
to  the  bent  edges  of  the  tin, 
and  to  the  wad,  securing  all 
firmly  together. 

The  charge  is  made  up  of 
six  cakes  or  rings  of  compressed 
powder  having  central  holes. 
The  bottom  cake  is  slightly 
convex  at  its  lower  surface,  to 
take  the  form  of  the  pressed 
paper  wad.  The  cartridge  is 
charged  by  rolling  the  six  cakes 
in  a paper  envelope,  and  inserting  the  cylinder  thus  formed  in 
the  case. 

By  a certain  degree  of  compression  a greater  force  is 
developed,  when  an  appropriate  surface  of  ignition  is  presented, 
by  the  explosion  of  a given  quantity  of  gunpowder,  than  in  a 
loose  state ; therefore  a charge  of  powder  when  compressed 
should  give  a greater  velocity  than  an  ordinary  charge  tired  in 
the  ordinary  way. 


BUILT-UP  GUNS. 


227 


A pasteboard  cup,  L,  is  placed  over  the  powder  and  filled 
wfith  lubricating  material,  having  first  inserted  a wad  of  tow. 
The  end  of  the  case  is  covered  with  a cloth  patch  secured  with 
a ribbon,  to  keep  the  pasteboard  cup  in  place.  The  edges  are 
then  slightly  crimped. 

The  priming-chamber,  CD,  is  filled  with  musket-powder, 
the  vent-hole  being  closed  with  a small  patch,  one  corner  of 
which  is  left  free. 

The  gas-check  arrangement  operates  as  follows  : The  pow- 
der in  the  priming-chamber  being  ignited  by  the  primer,  the 
flame  will  immediately  reach  the  charge  through  the  small 
holes  pierced  for  the  purpose,  when  the  gases  from  the  latter 
pressing  in  the  opposite  direction  flatten  out  the  indented  brass, 
which  carries  with  it  the  gas-check,  and  the  whole  closes  down 
upon  the  vent,  forming  a metallic  obstruction  to  the  escape  of 
the  gases. 

700.  In  the  forward  face  of  the  breech-screw  of  this  gun, 
a cupped  recess  0.4  in.  in  depth  is  snnk  to  receive  the  head  of, 
tlie  metallic  case.  This  recess  has  three  left-handed  spiral 
grooves,  in  which  the  head  of  the  case  is  firmly  grasped,  and  as 
if  embedded  after  firing.  On  opening  the  mechanism  and 
withdrawing  the  movable  breech,  these  projections  bring  with 
them  the  cartridge-case.  The  latter  strikes  with  its  open  end 
at  the  rear  opening  in  the  breech,  and  falls  to  the  ground.  In 
case  it  is  too  firmly  held,  it  may  be  readily  detached  by  un- 
screwing. The  Eastman  breech-closing  arrangement  operates 
Avell  in  this  gun,  except  a slight  upsetting  will  sometimes 
appear  in  the  threads  of  the  screw-box.  In  our  gun  several 
important  modifications  will  be  made  in  the  details  of  the 
screw-breech  by  increasing  the  length  of  the  screw,  adopting 
a better  form  of  thread,  and  the  insertion  of  a steel  thimble 
containing  the  screw-box,  in  the  rear  of  the  gun.  At  the  cen- 
tre of  the  I’ecess,  in  the  body  of  the  breech-screw,  is  the  vent, 
hy  which  the  flame  from  the  primer  passes  to  the  centre  of  the 
cartridge.* 

Section  Y. — German  Naval  Guns. 

701.  Nomenclature. — The  heavy  rifled  guns  for  vessels  are 
breech-loaders,  of  Krnpp’s  cast-steel,  all  hooped,  and  with 
round  breech  closure  and  axial  vent.  The  calibres  of  the  guns, 
that  is,  diameters  of  rifled  part  of  bore  from  land  to  land,  are 
as  follows : 


* U.  S.  Naval  Ordnance  Notes,  1873.— T/jfi  Eeffye  Gun. 


228 


NAVAL  ORDNANCE  AND  GUNNERY. 


11-inch,  or  28  centimetre, 96-pdr. 

lU-inch,  - or  2G  

9-inch,  or  23^  “ 90-pdr. 

8-inch,  or  21  “ T2-pdr. 

6.6- inch,  or  17  “ 3G-pdr. 

5.7- inch,  or  15  “ 21-pdr. 


Fig.  134. 


702.  Features  of  the  Maxufactcee. — The  great  fea- 
tures of  the  manufacture  are  tlie  forging  of  large  masses  from 
single  homogeneous  ingots  without  seams  or  welds,  the  forging 
and  rolling  of  hoops  without  welds,  the  use  of  very  heavy  ham- 
mers, and  the  quality  of  tlie  steel  which  contains  one-half  per 
cent,  of  carbon  and  a considerable  quantity  of  silicon. 

703.  Old  Krupp  Coxstructiox. — The  guns  are  made  at 
the  factory  of  Krui)p,  at  Essin,  in  Prussia,  lie  supplies  all  tbe 
cast-steel  guns  that  are  used  in  the  German  service.  Until 
within  a few  years,  he  made  all  his  heavy  guns  of  a single 
ingot,  cast,  forged,  and  turned ; but  this  method  left  the  gun 
open  to  the  serious  objection  of  liability  to  bursting  explosively 
or  without  Avarning.  No  matter  Avhat  care  has  been  used  in 
the  manufacture,  cast-steel  is  a treacherous  metal,  likely  to 
burst  Avithout  warning ; and  in  many  instances  the  failiu’e  of 
Krupp’s  guns  have  been  attended  with  disastrous  consequences. 

704.  Neav  Krupp  Coxstructiox. — Mr.  Krupp  has  aban- 
doned the  precedmg  method,  and  now  builds  up  all  his  larg-e 
guns  by  shrinking  hoops  of  steel  over  a central  tube  with  initial 
tension. 


BUILT-UP  GUNS. 


229 


Tlie  guns  consist  of  a central  tube,  and  the  single  (in  guns 
of  9-inches  calibre,  and  nji'U’ards  double)  layer  of  hoops  protect- 
ing those  parts  most  exposed  to  damage  by  the  expansion  of  the 
powder-gas. 

The  6.6-inch  and  S-inch  gnus  of  the  old  construction  have 
been  altered  to  the  new  on  account  of  its  greater  durability. 
The  outside  parts  are  named : the  breech  or  bottom-piece,  li 


(Fig.  135),  the  hooped  or  middle  piece.  A,  and  the  cone,  or 
chase,  C.  The  length  is  measured  between  the  planes  of  the 
base  of  the  breech  and  the  muzzle.  The  breech-piece  imme- 
diately abaft  the  hooped  piece  contains  the  wedge-hole,  H,  cut- 
ting through  at  right  angles  to  the  axis  of  the  bore.  In  the 
base  of  the  breech  is  the  hole  for  loading,  L (I  ig.  140) ; on 
each  side  of  the  hole  is  a hook,  V,  with  two  slots  for  the  hinges 
of  the  loading-box,  and  hooks  of  shell-bearer  ; farther  forward 
are  the  holes  for  the  sights. 

The  hooped  piece,  diminishing  in  fi'ont  by  steps  towards 
the  chase,  has  in  its  rear  the  protruding  end-hoop^  D (Fig.  135). 
In  its  front  part,  on  a broad  hoop,  are  the  rim-bases  and  trun- 
nions, whose  axes  pass  through  the  axis  of  the  piece.  On  top 
of  the  trunm'ous  are  the  screw-holes  for  sights.  The  after- 
edges of  the  end-hoop  and  of  the  bottom-piece  are  considerably 
rounded  off.  The  bore  extends  to  the  wedge-hole,  and  includes 
the  chamber,  the  seat  of  the  projectile  and  rifling.  The  cham- 
ber is  equal  in  diameter  to  the  diameter  of  the  bottoms  of  the 
grooves. 


230 


IsAVAL  OEDNAIfCE  AND  GUNNERY. 


forging 


Fig.  136. 


705.  The  Central  Thbe,  T,  is  very  massive  ; almost  a gun 
by  itself.  It  is  forged  and  turned  from  a single  ingot,  and 
loses  half  its  weight  in  the  lathe.  The  gun-blocks  are  cooled 
slowly  by  throwing  them,  after  hammering,  into  the  hot  ashes 
and  cinders  from  the  furnaces,  where  they  are  allowed  to 
remain.  Tins  tube  supplies  all  the  longitudinal  strength,  and 
projects  far  enough  to  the  rear  to  accommodate  the  breech 
closure.  It  is  not  tempered.  The  walls  are  0.8  of  a calibre 
thick  from  a point  over  the  middle  of  the  charge  to  the  point 
wliere  the  rings  terminate. 

700.  Hoors. — The  hoops  are  made  with  an  endless  fibre  by 
an  ingot  into  the  shape  shown  in  Fig.  136,  with  a slot 
through  the  middle  ending  in  holes.  This  slot  is 
pressed  with  wedges  into  a ring,  which  is  half  the 
diameter  and  twice  the  thickness  of  the  finished 
ring.  The  ring,  having  been  heated,  is  put  over 
the  central  roll  of  a machine  like  the  tire-rolling- 
machine  (Fig.  137).  The  rolls,  while  revolving,  gradually 
approach  each  other,  and  thus  the  hoop  is  rolled  to  its  proper 
size,  and  at  the  same  time  an  endless  fibre  is  developed  in  the 

direction  of  the  circumference ; 
they  are  cooled  by  a jet  of  water 
while  on  the  rolls;  this  prevents 
distortion.  They  are  then  heated 
and  shrunk  on  with  initial  ten- 
sion. They  are  kept  from  work- 
ing on  the  gun  by  key-rings,  a 
(Fig.  135),  which  are  lialf-hoops 
laid  into  scores  cut  to  receive  them. 

707.  Breech-plug. — For  the  hooped  guns  which  with 
heavy  charges  had  not  sufficient  durability,  the  cylindro-pris- 


Fig. 


V61 . — Machine  for  Rolling 
Hoops. 


Fig.  138. 


matic  wedge,  P (Fig.  139),  has  been  adopted.  It  slides  in  a 


BUILT-UP  GUNS. 


231 


horizontal  inortiso  of  the  same  shape  in  the  breech-piece.  The 
plug  is  made  of  steel,  the  wedge  and  cylinder  forming  one 
body ; the  rounded  part  is  on  the  rear  side,  as  that  gives  a 
greater  bearing-snrfaee.  It  is  generally  drawn  ont  on  the  left 
side,  except  in  turrets  or  when  the  position  of  the  gnns  may 
jecpiire  a change.  The  front  side  is  Hat  and  forms  the  bottom 
of  the  bore.  The  wx'dge  has  small  grooves  parallel  to  its  after- 
edge  oil  the  top  and  l)ottom  for  the  leading-lasts,  which  keep  it 
in  position  while  it  is  being  moved  ont  and  in. 

In  the  gnns  of  8-ineh  calibre  and  upwards,  the  ping  is 
moved  in  and  ont  by  a transporting-screw,  a.  In  the  smaller 
gnns  it  is  moved  by  hand.  The  transporting-screw  rests  in  a 
groove  on  the  npper  side  of  the  wedge,  and  has  a shoulder 
which  takes  against  'the  locking-plate,  h,  and  a rounded  end 
which  turns  in  a ring  at  the  other  end  of  the  wmdge  and  keeps 
the  screw  in  position.  The  screw  works  in  a nut,  c,  on  the 
npper  side  of  the  wedge-hole.  (Fig.  139.) 

The  transporting-screw  has  a scpiare  end  to  which  a crank. 


Fig.  139. 


f,  is  fitted  for  turning  it.  The  end  projects  through  a plate, 
0,  called  the  locking-plate.  This  plate  is  screwed  on  to  the 
extreme  end  of  the  wedge. 

In  a hollow  on  the  after-side  of  the  wedge  is  the  loching- 
screw,  d,  with  its  joint  against  the  locking-plate,  ont  of  which 
one  end  protrudes  square,  for  shipping  the  crank,  while  the 
other  end  rests  in  the  wedge  and  is  held  by  a pin.  ' It  may  be 
turned,  but  cannot  be  moved  in  the  direction  of  its  axis. 
Upon  it  is  the  nut,  e,  shorter  than  the  hollow,  with  several  rino’s 
cut  away  on  one  side,  but  with  one  full  end  ring  at  the  outer 


232 


NAVAL  ORDNANCE  AND  GUNNERY. 


Fig.  140. 


end.  Upon  the  latter  a projection,  u,  is  formed,  Tvhich,  coming 
out  of  a segment  of  the  locking-j)Jate,  may  be  turned  about 

one-third  of  a circle.  As 
soon  as  the  projection 
stops  the  turning  of  the 
nut,  it  can  be  pushed 
forward  or  back.  ^Vith 
closed  breech,  the  ring 
parts  of  the  nut  fit  into 
cuts,  17,  <7,  p,  in  the  gun ; 
but  when  open,  the  part 
not  having  rings  turns 
to  the  rear.  The  same 
crank,  f,  fits  both  screws. 
The  locking-chain,  o,  on  the  gun,  with  the  hook  on  the  locking- 
plate,  limits  the  movements  of  the  wedge. 

708.  Gas-chece. — To  pre- 
vent the  escape  of  gas  breech- 
wards  without  a perfect  me- 
chanical fit  of  the  parts  of  the 
breech,  a Broadwell-j)late,  h 
(Fig.  129),  and  ring,  i,  are 
used.  The  ring  is  a circle  of 
steel,  which  fits  into  a groove 
or  chamber  at  the  bottom  of 
the  bore  close  to  the  wedge- 
mortise.  As  an  aid  to  the 
Fig.  141.  steel  Broadwell-ring  of  the 

chamber,  a circular,  slightly  hol- 
lowed out  Broadwell-plate,  h (Fig.  138),  is  entered  into  the 

wedge,  which  is  cut  out  for  this 
pui'pose  on  its  front  side  at  h 
(Fig.  138),  so  that,  at  the  closing 
of  the  breech,  its  liin,  projecting 
a little  over  the  wedge,  meets 
the  ring,  which  also  projects  over 
the  front  side  of  the  wedge-hole. 
At  the  discharge  this  check  is 
closed  by  the  action  of  the  pow- 
der-gas, which  presses  the  thin 
edges  of  the  ring  against  the 
gim  and  plate.  The  plate  has 
circular  plates  of  thin  brass  be- 
hind it,  for  an  equalizing  spring 
support;  and  the  plate  is  kept 


BUILT-UP  GLmS. 


233 


in  position  bj  a pin  wbicb  is  screwed  into  tlie  wedge  at  tlie 
centre,  for  wliicb  tlie  plates  of  brass  are  pierced. 

709.  The  Yent-tube. — The  vent  is  in  the  direction  of  the 
axis  of  the  bore,  and  is  tilled  with  a vent-tube;  this  is  made  of 
steel,  cylindrical,  and  is  lined  with  copper,  more  or  less  conical, 
and  tits  exactly  into  its  place  in  the  wedge ; this  place  is  en- 
larged at  the  rear,  and  fitted  with  a thread  for  \h.Q  primer-hibe 
screw.  It  has  also  a broad  fiange  upon  whose  rear  side  the 
lock  for  confining  the  friction-primers  is  placed,  A (Fig.  112). 
This  consists  of  a fiat  cover  which  has  a cut  in  it  for  the  wire 
of  the  friction-primer,  and  it  has  a button  on  toji  for  handling 
it,  a.  It  turns  easily  on  its  hinge,  and  is  hollowed  out  on  the 
side  of  the  vent,  so  that  it  may  be  raised  by  the  escaping  gas, 
and  thrown  aside.  The  whole  lock  is  placed  in  a hollow  of 
the  wedge,  so  that  it  can  be  moved  at  pleasure  without  inter- 


CHAPTER  Y. 


- EITLIN^G-. 

Section  I. — Principles. 

710.  Definition. — A rifle  is  a fire-arm  which  has  cerlain 
spiral  grooves  or  “rifles’'  cut  into  the  surface  of  its  bore,  for 
the  purpose  of  communicating  a rotary  motion  to'  a projectile 
around  an  axis  coincident  with  its  flight. 

711.  Oeigin  of  Rifling.— The  rifle-principle  was  first 
developed  in  small-arms.  W ith  the  smooth-bore  gun  the  wind- 
age which  allowed  the  ball  to  be  entered  freely  at  the  muzzle 
of  the  piece  gave  rise  to  great  inaccuracy  of  flight,  from  the 
fact  that  the  projectile  was  thereby  caused  to  ballot  along  the 
boi’e,  and  be  projected  in  a direction  due  to  its  last  contact,  and 
this  deviation  was  complicated  by  a motion  of  rotation  gen- 
erated at  the  instant  of  the  last  contact  of  the  ball  with  the  bore, 
and  pei-petiiated  throughout  the  entire  flight  of  the  projectile. 

712.  To  avoid  the  bad  effects  of  the  shocks  in  the  bore, 
windage  was  suppressed,  the  ball  made  of  a calibre  equal  to 
that  of  the  piece,  and  straight  grooves  cut  in  the  barrel ; which 
diminished  the  surface  in  contact  with  the  projectile,  thus  ena- 
bling it  to  be  pushed  home  with  slight  pressure.  By  accident- 
ally making  these  grooves  inclined,  it  was  immediately  seen 
that  increased  accuracy  was  given  to  the  weapon ; but  the 
science  of  the  day  "was  unable  to  assign  a reason  for  tins  superi- 
ority. 

713.  About  the  year  1600  the  rifle-musket  began  to  be  used 
as  a military  weapon  for  flring  spherical  bullets.  It  is  well 
known,  however,  that  this  means  of  obviating  the  effects  of  the 
irregular  rotary  movement  of  the  projectile  was  applied  long 
before  the  nature  of  the  difficulty  wdiich  it  remedied  was  itself 
apprehended. 

711.  The  rotation  of  the  ball  upon  a given  axis,  by  means 
of  the  tight-fltting  spiral  groove,  and  the  consequent  invariable 
presentation  to  the  resistance  of  the  atmosphere,  of  the  surface 
originally  placed  in  that  direction,  would  seem  to  indicate  be- 
yond the  possibility  of  misconception,  the  advantage  that  was 
to  be  obtained  from  it.  And  yet  it  is  only  in  our  own  time 
that  the  round  ball  has  given  way  in  the  rifle  to  the  conical  or 


RIFLING. 


235 


elongated  projectile.  The  great  merit  of  the  arm  was  conse- 
quently of  little  account,  because  the  resistance  experienced  by 
the  round  ball  from  the  atmosphere  was  nearly  the  same, 
whether  tired  from  one  piece  or  another;  while  with  light 
charges  there  was  a certain  decrease  of  initial  velocity  from  the 
friction  in  the  rifle.  But  with  the  conical  or  elongated  projec- 
tile the  surface  of  the  transverse  section  was  decreased,  while 
the  weight  remained;  therefore  there  was  less  resistance  to 
overcome  with  the  same  power. 

715.  It  is  obvious,  however,  that  the  introduction  of  elon- 
gated projectiles  would  follow  that  of  rifled-bores;  and,  indeed, 
it  is  very  doubtful  if  cannon  would  ever  have  been  rifled  were 
it  not  for  the  sake  of  firing  such  projectiles — for  the  advan- 
tage of  such  accuracy  as  might  be  given  to  a spherical  projectile 
would  very  probably  be  counterbalanced  by  the  curved  and 
irregular  ricochet  that  rotation  imparts  to  it,  and  the  increased 
strain  on  the  gun.  Thus  rifling  being  necessary  for  the  employ- 
ment of  elongated  projectiles,  and  such  projectiles  being  essen- 
tial to  the  success  of  rifled  cannon,  the  two  have  become  insep- 
arably connected  in  the  mind. 

716.  Difficulty  of  Loading. — The  great  difficulty  of  loading 
the  rifle  prevented  it  for  a long  time  from  being  generally  used 
in  regular  warfare,  but  the  improvements  which  have  been  made 
of  late  have  entirely  overcome  this  difficulty,  and  rifles  are  now 
used  almost  univei'sally  in  place  of  smooth-bored  small-arms. 

717.  INTRODUCTIOJI  OF  RIFLE-CARROR.— The 
general  adoption  of  rifled  small-arms  necessitated  the  introduc- 
tion of  rifled-cannon.  It  is  plain  that  the  principle  has  applica- 
tion to  all  sizes  of  projectiles,  and  would  therefore  be  used  for 
the  heaviest  ordnance  as  well  as  for  the  smallest.  Contempora- 
neous attempts  so  to  adapt  it  have  not  been  wanting,  but  they 
are  in  many  cases  isolated  in  point  of  time  and  connection. 

The  first  persevering  and  rational  efforts  to  apply  the  rifle- 
principle  to  cannon  were  initiated  some  twenty  years  since,  and 
the  names  of  Wahrendorff,  Cavalli,  Lancaster,  and  others,  are 
identified  with  the  first  efforts  to  overcome  the  difficulties — of 
no  ordinary  character — that  beset  the  question. 

718.  Difficulty  of  Construction. — The  yielding  nature  of 
lead  renders  the  application  of  the  rifle-principle  of  easy  accom- 
plishment in  the  case  of  small-ainns  ; but  such  is  not  the  case 
with  rifle-cannon,  where  the  projectiles  are  made  of  iron. 

The  application  of  this  principle  to  cannon  also  required  an 
increase  of  strength  in  the  piece. 

719.  The  greater  the  Aveight  and  the  length  of  a projectile, 
the  greater  is  the  opposition  from  inertia  and  friction  which  it 


236 


NAVAL  ORDNANCE  AND  GTJNNERT. 


offers  in  the  bore  to  the  expansion  of  the  ignited  charge,  and 
this  opposition  is  considerably  augmented  if  the  projectile  is 
constrained  to  travel  through  the  bore  in  a spiral  course. 
Hence  it  is  not  difficult  to  comprehend  why  a rined-gun  must 
he  of  a stronger,  tougher,  and  more  elastic  material  than  is 
necessary  for  a smooth-bore  gun  in  which  the  spherical  projec- 
tile yields  promptly  to  the  first  impulse  of  the  powder-gas  to 
which  it  presents  half  its  surface,  and  hounds  freely  forward 
through  the  bore,  almost  unimpeded  by  friction  ; while  the 
sti’ain  on  the  gun  is  immensely  relieved  by  the  comparatively 
great  windage. 

720.  Again,  as  the  explosive  power  of  a cartridge,  as  well 
as  the  inertia  and  friction  of  a projectile,  increase" as  the  cubes 
of  their  respective  weights,  while  the  surface  of  the  chamber 
and  the  base  of  the  projectile  against  which  the  powder-gas  acts 
increase  only  as  the  squares,  it  folloAvsthat  the  larger  the  charge 
and  the  heavier  the  projectile,  the  harder  and  stronger  mxist  be 
the  inner  barrel,  or  else  the  slower  must  be  the  combustibility 
of  the  powder  used. 

721.  The  difficulty  of  perfecting  more  powerful  guns  for 
rifle-cannon  than  previously  existed,  has  been  very  great ; nor 
have  we  by  any  means  reached  perfection  in  the  construction 
of  such  guns.  The  successful  application  of  the  rifled  principle 
and  the  possibility  of  throwing  enormous  shells  with  the  great- 
est initial  velocity  have  exhibited  the  importance  of  the  strong- 
est cannon  and  the  utility  of  the  largest  calibres,  but  their 
development  must  be  in  harmony  with  the  progress  of  the 
manufacturing  arts. 

722.  Progress  nsr  Coxstetjction. — The  progress  of  the  art 
of  war  depends  essentially  upon  that  of  the  sciences  and  manu- 
factures, for  the  manner  of  hghting  depends  upon  the  character 
of  the  arms  which  we  possess.  These  will  be  more  effective,  as 
their  mode  of  construction  is  more  perfect,  and  as  the  means 
employed  in  their  manufacture  produce  greater  strength  and 
precision. 

This  is  particularly  the  case  with  reference  to  cannon,  in 
evidence  of  which  we  have  only  to  call  to  mind  the  great  revo- 
lution in  warfare  which  has  taken  place  since  their  introduc- 
tion, and  which  is  continually  taking  place  as  the  means  of  per- 
fecting cannon  increase. 

It  is  only  of  late  years  that  our  knowledge  of  the  metalhirgy 
of  iron,  and" our  ability  to  manufacture  and  handle  large  masses 
of  that  metal,  have  rendered  possible  the  fabrication  of  the 
enormous  pieces  of  the  present  day. 

But  now  the  great  improvements  which  have  been  intro- 


EIFLING. 


237 


duced  in  the  manufacture  of  iron,  in  the  fabrication  of  cannon, 
and  in  the  facilities  for  the  transportation  and  handling  of 
heavy  guns,  render  possible  the  success  of  cannon  of  mammoth 
proportions. 

723.  Designing  Rifle-cannon. — In  designing  rifle-cannon, 
the  practicability  of  manufacture  and  the  durability  of  struc- 
ture must  be  ascertained.  The  weight,  calibre,'  length,  system 
of  rilling,  weight  and  shape  of  projectile,  etc.,  etc.,  must  be  all 
scientifically  calculated  so  as  to  ensure  excellence  in  range,  ac- 
curacy, and  penetration ; and  then  each  and  all  of  these  con- 
structional details  are  liable  to  alteration,  should  the  thorough 
trial  of  a specimen  gun  render  any  amendment  advisable. 

721.  Early  Experiments.^ — The  first  comprehensive  experi- 
ment with  rified-cannon  appears  to  have  been  made  in  Russia, 
about  1836,  on  the  invention  of  a Belgian,  but  did  not  prove 
successful. 

In  1815,  Cavalli,  a Sardinian  officer,  experimented  with  a 
breech-loading  cannon  which  was  rifled  with  two  grooves,  for  a 
plain  iron  projectile,  adapted  to  fit  them.  In  the  next  year, 
Wahrendoj’ff,  of  Sweden,  fitted  heavy  projectiles  to  take  the- 
rifling  by  affixing  lead  to  their  elongated  sides  by  means  of 
grooves  cut  in  them.  And  not  long  after  this,  Timmerhaus,  of 
Belgium,  invented  an  expanding  sahut,  which,  being  fitted  to 
the  base  of  the  projectile,  was  forced  into  the  rifle-grooves  and 
thus  gave  rotation. 

' In  these  early  experiments  we  find  the  germs  of  the  leading 
systems  of  the  present  day.  The  solid  projectile,  fitted  to  enter 
the  grooves  of  the  gun ; the  compression  of  a soft  covering  on 
the  projectile  by  the  lands  of  the  gun ; and  the  expansion  of 
the  rear  of  the  projectile  by  the  press  me  of  the  powder  to  till 
the  grooves  of  the  gun. 

725.  OBJECT  OF  RIELINGr. — The  object  of  rifling  a gun 
is  to  increase  its  accuracy  of  fire,  and,  by  enabling  elongated  to 
be  substituted  for  spherical  projectiles,  to  obtain  from  it  longer 
ranges. 

Rifling  diminishes  the  deviations  of  ordinary  projectiles,  due 
to  the  following  causes  : 

1st.  Want  of  uniformity,  in  figure  and  weight,  around  the 
longitudinal  axis  of  the  projectile,  passing  through  the  centre 
of  gravity. 

2d.  Position  of  the  centre  of  gravity,  before  or  behind  the 
centre  of  figure. 

3d.  Resistance  of  the  air. 

I.  By  rotating  the  projectile  around  its  longitudinal  axis, 
the  direction  of  these  deviations  is  so  rapidly  shifted  from  side 


238 


NAVAL  ORDNANCE  AND  GUNNERY. 


to  side,  that  the  projectile  has  no  time  to  go  far  out  of  its  course 
either  way. 

II.  The  velocity  of  this  rotation  is  such  as  to  make  the  axis 
stable  on  leaving  the  bore,  and  to  counteract  the  pressure  of  the 
air  tending  to  turn  the  projectile  over,  or  render  it  unsteady  in 
liiglit. 

III.  A given  weight  of  projectile  can  he  put  into  such  a 
form  as  to  oppose  the  least  practicable  cross-sectional  area  to  the 
air,  and  thus  to  receive  the  least  practicable  retardation  of 
velocity. 

726.  Advantages  of  Elongated  Peojectiles. — Certain 
peculiar  advantages  follow  from  the  rotation  of  the  projectile, 
causing  it  to  present  the  same  part  to  the  front  throughout  its 
flight. 

It  becomes  possible  to  make  a much  simpler  percussion-fuze, 
because  it  is  only  necessary  to  provide  for  action  in  one  dii’ec- 
tion  in  place  of  every  possible  direction. 

Shells  required  to  act  towards  the  front  in  any  peculiar  way 
have  their  bursting-charge  and  metal  placed  with  a view  to 
this  object.  So,  again,  the  centre  of  gravity  may  be  brought  to 
any  desired  part  of  the  shell ; and  this  is  an  important  feature 
in  the  construction  of  projectiles. 

Pilling  gives  the  power  of  altering  the  form  of  projectiles  at 
will.  The  head  may  be  made  of  any  desired  shape,  for  penetra- 
tion or  flight.  The  projectile  may  be  elongated  so  as  to  give  a 
diminished  surface  for  any  resisting  medium  to  act  upon  ; thus 
in  flight,  velocity  is  kept  up  and  the  range  extended,  or  on  im- 
pact greater  penetration  is  obtained. 

Weight  for  weight,  the  same  effect  may  generally  be  pro- 
duced with  an  elongated  projectile  by  using  a smaller  charge  of 
powder  than  Avith  a spherical  one. 

It  follows  from  the  flight  of  an  elongated  projectile  meeting 
Avith  less  resistance  from  the  air,  and  keeping  up  its  A'elocity 
better,  that  at  all  but  A'ery  short  ranges  the  trajectory  is  flatter  ; 
hence  the  probability  of  hitting  an  ordinary  object  is  greater. 

The  poAver  to  vary  the  length  of  the  elongated  projectile  en- 
ables all  those  for  the  same  gun  to  be  made  of  the  same  Aveight, 
and  hence  to  require  the  same  elevations  Avith  the  same  charge 
of  poAvder.  Or  it  is  possible  to  make  a projectile  specially  lieaA-y 
if  required.  This  obviously  camiot  be  the  case  Avith  spherical 
projectiles,  AAdiich  must  be  of  the  same  size. 

727.  Disadvantages  of  Elongated  Peojectiles. — The  chief 
disadvantages  are,  bad  ricochet,  increased  complication,  and  ex- 
pense of  manufacture,  liability  to  injury  arising  from  the  neces- 
sity of  soft  studs,  expanding  rings,  or  a soft  lead  coat ; increased 


RIFLING. 


239 


strain  on  tlie  gun,  besides  greater  probability  of  jamming  and 
injury  to  tbe  bore,  uncertainty  of  time-fuzes. 

728.  METHOD  OF  EIFLIbTG. — To  rifle  a flre-arm,  spiral 
grooves  are  cut  in  tbe  surface  of  tbe  bore,  into  wliicb  the  pro- 
jections or  soft  metal  coating  of  the  projectile  are  made  to  enter. 

The  grooves  may  be  of  any  number,  and  may  extend  par- 
tially around  the  bore,  or  once,  twice,  or  several  times  in  its 
length.  They  may  be  of  the  same  pitch  or  curvature  through- 
out, or  the  twist,  if  desired,  may  increase  in  curvature  towards 
the  muzzle.  It  is  essential,  however,  that  all  the  grooves  be  of 
the  same  curvature,  and  exactly  parallel  to  each  other ; their 
object  being  to  impress  upon  the  projectile  a rotating  motion 
about  its  axis  of  progression,  and  thus  keep  it  in  a straight  line 
as  it  spins  forwai'd.  The  motion  of  a top  holding  itself  upright 
while  rapidly  spinning,  illustrates  the  principle  of  the  rifle. 

729.  Lands. — -The  spaces  between  the  grooves  are  called 
‘■'•landsP  Where  the  grooves  are  very  wide,  and  the  lands 
very  narrow,  they  are  termed  “ riljsP 

730.  Calibre. — The  calibre  of  a rifle-gun  is  measured  across 
the  lands.  In  the  ease  of  a rib-rifled-gun,  it  is  measured  to  the 
bottom  of  the  grooves. 

731.  Fokm  of  Gkoove.- — -The  form  of  the  grooves  and  their 
number  vary  very  much  according  to  the  method  of  rifling. 

The  form  of  the  groove  is  determined  by  the  angle  which 
the  tangent  makes  at  any  point  with  the  corresponding  element 
of  the  bore.  If  the  angles  be  equal  at  all  points,  the  groove  is 
said  to  be  uniform.  If  they  increase  from  the  breech  to  the 
muzzle,  the  grooves  are  called  increasing.,  or  the  rifling  has  a 
gaining  twist. 

732.  Twist  is  the  term  generally  used  to  express  the  inclina- 
tion of  a groove  at  any  point,  and  is  measured  by  the  length  of 
a cylinder  corresponding  to  a single  revolution  of  the  spiral. 
This,  however,  does  not  convey  a correct  idea  of  the  inclination 
of  a groove. 

A correct  measure  of  the  inclination  of  a rifle-groove  at  any 
point,  is  the  tangent  of  the  angle  which  it  makes  with  the  axis 
of  the  bore ; and  this  is  always  equal  to  the  circumference  of 
the  bore  divided  by  the  length  of  a single  revolution  of  the 
spiral,  measured  in  the  direction  of  the  axis. 

731.  Unifokii  Twist. — Let  ABC  (Eig.  113)  be  a right-an- 
gled triangle,  in  which — 

EC  = circumference  of  the  bore  of  a gun, 

AB  = length  of  the  bore. 

How  suppose  the  triangle  ABC  to  be  wrapped  around  the 


240 


NAVAL  ORDNANCE  AND  GUNNERY. 


surface  of  tire  bore  as  in  Fig.  143,  so  that  B and  C meet.  AC  will 
be  the  lielix^  or  curve  of  the  groove.  IS^ow  in  Fig.  143  the  groove 
makes  a complete  turn  in  the  length  of  the  bore  ; but  in  ordinary 


Fig.  143. 


rifle-guns  the  twist  is  more  gradual,  making  less  than  one  turn 
in  the  boi’e. 

In  the  ease  before  us,  AB  equals  the  length  of  ilfling  due  to 
one  turn,  that  is,  the  distance  travelled  by  the  projectile  while  it 
is  turning  on  its  axis.  AC  is  the  total  length  of  spiral  and  Q the 
angle  of  twist,  or  angle  of  the  rifling.  Let  n = number  of  cah- 
bres  in  which  the  projectile  makes  one  turn. 


tan  Q 


^ _ 

AB  “ 

Tt  X calibre 


number  of  calibres  X calibre 


7t  Tt 

number  of  calibres  n 


735.  Uniformly  Increasing  T^VIST. — Wlien  this  system  is 
adopted,  the  grooves  start  in  a direction  parallel  to  the  axis  of  the 
bore,  and  the  twist  increases  uniformly  towards  the  muzzle. 

In  the  Fig.  144,  ABCO  denotes  the  development  of  the  bore, 
and  CM  that  of  a groove.  The  origin  of  the  co-ordinate  axes  is 
taken  at  the  commencement  of  the  groove  at  the  bottom  of  the 
bore ; the  axis  of  Y is  parallel  to  the  axis  of  the  bore. 

The  curve  OM  is  tangent  to  OA  at  O,  since  the  projectile 
starts  in  the  direction  OA.  Let  <p  denote  the  variable  angle 
between  OX  and  the  direction  of  the  curve  031.  If  the  twist 
increases  uniformily,  tan  ip  will  decrease  uniformily  as  the 

ITl 

ordinate  increases.,  and  u^e  shall  have  tan  o = — , m being  an 

^ y 

imdetermined  constant. 


RIFLING. 


241 


But 


integrating, 


, d%!  m 

ydy  — mdx  j 

= 2 mx  -|-  K 


,(4 


The  constant  of  integration  {K')  is  zero,  since  the  curve  passes 
through  the  origin,  (a)  is 
the  ecpiation  to  a parabola 
referred  to  the  vertex  and 
principal  axes. 

In  the  Figure,  MT  is 
tlie  tangent  at  M,  and 
MM'  equals  AB  = ttc,  c 


being  the  calibre  of  the 
gun. 

Also  M'T  is  put  equal 
to  no,  n denoting  the 
number  of  calibres  in 
which  the  projectile  mahes 
one  turn  after  leaving  the 
muzzle. 

To  determine  m,  putting  ^'for  the  value  which  cp  has  at  M 
we  have 


tan  (p'  — 


on, 


I ’ 


, , , oiG  n 

also  tan  w — — = - 


m — 


Ttc 

In 

71  ' 


7T 


Whence  the  equation  to  the  curve  is 


„ ^hi 

y = 

By  means  of  equation  (5)  the  curve  is  easily  traced, 

736.  CoMP^VRATH^E  ADVANTAGES. — The  loricreasing-Tomst. — 
The  advantages  claimed  for  this  method  of  rifling  are,  that  the 
projectile,  not  being  forced  to  take  the  whole  twist  of  the  rifling 
at  once,  moves  more  readily  from  its  seat,  and  thus  the  initial 
strain  upon  the  breech  of  the  gun  is  reduced,  thereby  prolong- 
ing its  life ; also  that  the  bearings  on  the  projectile  are  not  lia- 
ble to  be  torn  off. 

Theoretically  it  would  seem  that  a system  of  rifling  which 
permits  the  projectile  to  move  directly  forward  from  its  seat,  at 

6 


242 


NAVAL  ORDNANCE  AND  GUNNERY. 


the  moment  of  ignition  of  the  charge,  must  he  more  favorable 
to  endurance  than  one  which,  hy  impeding  the  first  movement 
of  the  projectile  in  the  bore,  narrows  the  space  for  the  expand- 
ing gas,  and  consequently  bi’ings  a greater  pressure  on  the 
breech  of  the  gun. 

But  practically  this  method  does  not  appear  to  be  success- 
ful, in  the  enormous  cannon  of  recent  construction. 

737.  The  greatest  objection  to  the  increasing-twist  is  that  it 
cannot  be  used  with  a long  bearing  of  projectile.  Indeed,  the 
theoretical  bearing,  whether  it  is  a soft  metal  ring,  a strip,  or  a 
stud  is  infinitely  short — a mere  line — and  practically,  length  of 
bearing  is  only  obtained  by  a constant  molding  of  the  projectile 
to  the  new  angle  of  rifling,  so  that  the  portion  of  the  projectile 
intended  to  take  the  grooves,  must  be  short  and  also  soft,  for  if 
it  cannot  obtain,  by  changing  it  figures,  more  bearing  on  the 
grooves  than  on  a mere  line,  it  will  undoubtedly  cut  the  grooves, 
thus  increasing  friction,  and  soon  ruining  the  bore. 

In  the  absence  of  further  experiments,  it  would  hardly  be 
safe  to  conclude  that  long  bearings  will  not  prove  indispensable 
to  the  heavy  projectiles  and  high  velocities  that  are  now  re- 
quired. 

A projectile,  if  balanced  on  weakening  studs  in  each  groove 
(Art.  782),  is  liable  to  break  up  through  the  stud-holes,  thereby 
injuring  the  gun. 

To  rapidly  rotate  an  iron  cylinder,  say  12  inches  in  diameter 
and  three  calibres  in  length,  weighing  nearly  a third  of  a ton, 
by  a ring  of  such  points,  is  very  likely  to  produce  a wahljlmg 
motion  and  unsteady  movements  in  flight,  with  reduced  range. 
Aery  rapid  twist,  although  it  conduces  to  steadiness  of  motion, 
■cannot  be  o:iven  because  small  bearings  will  not  endure  the 
great  effort  necessary. 

738.  The  Uniform  Twist. — In  this  case  the  same  angle  of 
twist  obtains  throughout,  from  the  seat  of  the  projectile  to  the 
muzzle ; it  is  more  simple  in  construction,  and  as  accurate  in 
results. 

The  effort  of  rotation  may  be  diffused  over  a long  centring 
bearing,  extending  along  the  whole  cylindrical  body  of  the  pro- 
jectile, which  is  an  advantage  of  great  importance,  and  when 
the  projectile  is  free  to  escape,  its  motion  will  be  much  more 
uniform  than  if  it  received,  as  it  were,  a severe  wrench  on  leav- 
ing the  muzzle,  while  it  is  not  believed  that  the  life  of  the  gun 
is  materially  affected  by  differences  of  powder  pressure  within 
the  possible  limits  which  can  obtain,  between  guns  rifled  with 
the  same  final  angle  of  twist,  on  the  uniform  and  on  the  increas- 
ing systems. 


EIFLINa. 


243 


739.  Initial  Velocity  of  Eotation. — Let  V be  tbe  initial 
velocity  of  the  projectile  or  space  Avliich  it  'woiilcl  pass  over  in 
one  second,  in  the  direction  of  flight,  moving  with  the  velocity 
wdth  which  it  leaves  tlie  piece,  and  I the  distance  passed  over  by 

the  projectile  in  making  one  revolution  ; then  -j  will  be  the 

V 

number  of  revolutions  in  one  second  and  2 — the  angular 

0 

velocity  of  the  projectile  at  the  muzzle. 

The  velocity  of  rotation' of  a point  on  the  surface  is  given 
by  the  expression 

r w = 2 7T  T-j-, 

V 


in  which  r is  the  distance  from  the  axis  of  motion,  and  w is  the 
angular  velocity. 

740.  Velocity  of  Rotation. — The  velocity  of  rotation  re- 
quired by  a projectile  will  depend  chiefly  upon  initial  veloc- 
ity^ the  form,,  the  density^  the  distribution  of  the  material,  and 
ih.'d  position  of  the  centre  of  gravity  of  the  projectile  ; therefore, 
there  is  a particular  inclination  of  grooves  which  is  best  suited 
to  each  calibre,  form  of  projectile,  charge  of  powder,  etc. 

This  has  not  yet  been  fully  determined  by  experience,  and 
the  consequence  is  that  a wide  diversity  of  twists  is  employed  in 
different  services  and  by  different  experimenters.  A long 
course  of  very  careful  experiments  is  necessary  to  establish  laws 
that  could  be  generally  applied. 

741.  Initial  Velocity. — As  the  initial  velocity  of  a projec- 
tile is  increased,  so  will  the  resistance  of  the  air  tending  to 
overturn  the  projectile  be  greater. 

742.  Form. — Long  projectiles  require  a more  rapid  rotary 
motion  than  short  ones  of  equal  weight,  for  the  resultant  of  the 
air  acts  with  a greater  leverage  as  the  length  of  the  projectile 
is  increased,  tending  to  give  it  a rotation  round  its  shorter 
axis. 

The  cause  of  this  tendency  to  turn  over  in  flight,  is  apparent 
from  the  accompanying  diagrams.'^  As  the  effect  of  the  pres- 
sure of  the  air  differs  according  to  the  shape  of  the  head  of  the 
projectile,  both  a conoidal  and  a flat  head  are  here  given  in 
Figs.  145  and  146. 

In  each  of  these  Figures,  R,  representing  the  resultant  of 
the  air’s  resistance,  acts  below  a,  and  is  half-ivay  between  the 
dotted  lines,  which  include  between  them  a space  representing 


Owen. 


2M 


NAVAL  ORDNANCE  AND  GUNNERY. 


tLo  opposing  current  of  air;  it  is  evident  these  lines  should 
he  parallel  to  AB. 


Fig.  146. 


The  effect  of  R in  Fig.  145  is  to  give  the  projectile  a rota- 
tion around  one  of  its  shorter  axes,  the  head  being  turned  up, 
as  shown  by  the  dotted  lines.  In  fact  a pressure  exerted  any- 
where and  at  any  angle  between  a and  that  is,  before  and  be 
low  the  centre  of  gi-avity,  G,  will  have  a tendency  to  raise  the 
head  ; and  a force  exerted  behind  and  below  G,  between  h and 
c,  will  have  a tendency  to  depress  it. 

In  Fig.  146,  the  pressure,  B,  will  not  raise  but  depress  the  head, 
as  shown  by  the  dotted  lines  ; and  if  E-  acts  anywhere  between 
a and  ?»,  the  same  effect  will  be  produced ; but  if  E,  acts  be- 
tween h and  c,  the  head  will  be  raised  as  with  the  eylindi-o- 
conoidal  projectile.  (Fig.  145.) 

It  is  necessary  to  give  a flat-headed  projectile  a greater 
velocity  of  rotation  than  a conoidal  or  oy^^'a^pointed  projectile ; 
for  the  current  of  air  meeting  the  projectile,  instead  of  having 
merely,  as  with  the  latter  iorm,  to  pass  around  the  pointed 
head,  presses  with  the  flat  head  upon  a surface  almost  at  right 
angles  to  the  previous  direction  of  the  cm’rent,  and  consequently 
exerts  a very  much  greater  force  proportionally,  tending  to 
overturn  the  projectile. 

143.  Density. — The  greater  the  density  of  a projectile,  the 


EIFLIXG. 


245 


less  ■will  its  velocity  of  rotation  be  decreased  by  the  resistance  of 
the  air  during  the  time  of  flight,  because  of  its  greater  mo- 
mentum. For  instance,  a leaden  shot  would  retain  its  velocity 
of  rotation  longer  than  one  of  iron ; consequently,  as  the  densi- 
ties of  projectiles  are  increased,  so  may  their  respective  veloci- 
ties of  rotation  be  diminished. 

744.  Distribution  of  the  Material. — K.  hollow,  elongated 
projectile  will  be  steadier  during  flight  than  a solid  shot  of 
equal  weight,  for,  the  mass  being  distributed  farther  from  the 
axis,  the  radius  of  gju-ation  is  lengthened.  Thus  it  is  found  in 
practice  that  elongated  shells  are  steadier  in  flight  than  shot  from 
the  same  gun,  Avhon  the  latter  are  of  the  same  weight  as  the  shell. 

745.  Position  of  the  Centre  of  Gravity . — If  the  centre  of 
gravity  of  a projectile  is  very  far  forward,  as  in  Fig.  147, 


the  resultant  of  the  resistance  of  the  air  acting  at  b behind 
the  centre  of  gravity,  the  hinder  part  of  the  projectile  would  be 
presaed  upwards,  if  the  velocity  of  rotation  be  very  low,  so  that 
the  axis  might  correspond  very  nearly  during  flight  with  a tan- 
gent to  the  trajectory. 

In  this  case  an  iri-egular  motion  of  the  axis  will  generally 
result  from  the  opposite  tendencies  of  the  forcies  which  act 
upon  the  shot ; the  air  endeavoring  to  press  up  the  hind-pai-t  of 
the  projectile,  while  the  rotatory  motion  resists  a,ny  change  in 
the  direction  of  the  longer  axis.  With  the  centre  of  gravity  in 
this  position,  there  is  little  fear  of  the  projectile  turning  over 
even  with  a low  velocity  of  rotation  ; but,  in'  order  that  the  axis 
may  be  stable,  a rapid  rotatory  motion  must  be  given  to  prevent 
any  “ wabbling  ” which  might  arise  from  the  cause  just  explained. 

Shoidd  the  centre  of  gravity  be  situated  near  the  base,  a 
very  high  velocity  of  rotation  is  requisite  to  compel  the  projec- 
tile to  proceed  head  flrst.  In  Fig.  148,  the  pressure,  E,  of  'the 
air  acting  at  b would  doubtless  turn  up  the  point  a and  cause 


246 


NAVAL  ORDNANCE  AND  GUNNERY. 


the  projectile  to  rotate  around  its  shorter  axis,  unless  counter- 
halanced  by  a very  rapid  rotatory  motion  around  the  larger  axis. 


a 


Fig.  148. 


746.  Conclusions. — A very  high  velocity  of  rotation  is  objec- 
tionable for  the  following  reasons;  That  the  strain  upon  the 
metal  of  the  cannon  will  be  very  great,  as  the  charge  must  be 
comparatively  large,  and  the  grooves  will  require  a shaiqa  twist, 
mnch  resistance  being  thereby  caused  to  the  motion  of  the  pro- 
jectile ; that  the  projectile,  after  grazing,  will  deflect  considera- 
bl}- ; and  that,  shouid  the  projectile  be  a shrapnel,  the  pieces 
would  spread  laterally  to  too  great  a distance  to  be  effective. 

It  Avill  generally  be  sufficient,  as  far  as  accuracy  is  concerned, 
to  give  an  elongated  projectile  such  a velocity  of  rotation  that 
the  axis  may  be  stable  during  the  whole  time  of  flight  for  the 
longest  required  range ; should  the  rotation  be  not  sufficiently 
rapid  at  any  part  of  the  trajectory,  the  axis  of  the  projectile  will 
become  unsteady,  and  inaccuracy  of  fire  will  be  the  result. 

To  determine  theoretically  the  velocity  of  rotation  which 
ought  to  be  given  to  a projectile  of  definite  form  would  be  a very 
difficult  problem,  and  therefore  recourse  must  be  had  to  actud 
experiment  to  obtain  approximately  the  velocitv  required. 

747.  CTIAKACTEli  OF  OROOVES.— The  width  of  the 
groove  generally  depends  on  the  diameter  of  the  bore,  and  the 
peculiar  manner  in  which  the  groove  receives  and  holds  the 
projectile. 

Wide  and  shallow  grooves  are  more  easily  filled  by  the  ex- 
panding portion  of  a "projectile  than  those  which  are  narrow 
and  deep ; and  the  same  holds  true  of  circular-shaped  grooves 
when  compared  to  those  of  an  angular  form.  An  increase  in  the 
number  of  grooves  increases  the  firmness  with  which  a projectile 
is  held,  by  adding  to  the  number  of  points  which  bear  upou  it. 

The  effect  of  decreasing  the  depth  of  rifle-grooves  is,  gener- 
ally, to  increase  the  accuracy  but  diminish  the  range.  The  in- 
crease of  accuracy  undoubtedly  arises  from  the  fact  that  the 
projectile  is  held  more  firmly  by  the  grooves  as  it  passes  along 
the  bore;  while  the  diminution  of  range  arises  from  an  increase 
of  friction  between  the  projectile  and  the  grooves. 


RIFLING-. 


2i7 


The  depth  of  the  grooves  has  an  obvious  influence  upon  the 
strain  brought  upon  the  gun,  and  the  extent  of  the  bearing-sur- 
face recpiired  to  rotate  the  projectile  will  depend  upon  its 
velocity  and  the  angle  of  twist.  With  a high  velocity  or  a 
sharp  twist,  shallow  grooves  w’ould  strip  a soft  metal  bearing,  or 
cut  a hal'd  one. 

7 iS.  Loading  and  Driving  Edge. — A 
rifle  projectile  both  on  entering  and  leav- 
ing the  bore,  is  dri\'en  by  a force  act- 
ing along  its  axis,  and  rotation  is  given 
by  the  projections  coming  against  the 
spiral  formed  by  the  edge  of  the 
groove.  Thus,  in  Fig.  149,  if  the  projec- 
tile was  pushed  base  first,  the  studs  would 
move  against  the  loading -edge.,  CC,  of 
the  grooves,  while  if  pressure  were  ap- 
plied to  the  base  so  as  to  move  it  head 
first,  the  studs  would  meet  the  driving- 
edge,  DD,  and  work  along  it. 

749.  Advantage  of  liodial  Bearing. 

— A great  source  of  strain  from  rifling  is 
due  to  the  rvedging  of  the  projectile  in 
all  grooves  of  which  the  bearing-sides  do 
not  lie  in  the  plane  of  the  diameter  of 
the  bore.  For  instance,  the  inertia 
of  a jirojectile  rotated  by  the  groove  CD, 

Fig.  150,  tends  only  to  rotate  the  gun 
in  the  opposite  direction,  but  the  greater 
part  of  the  pressure  imposed  in  the 
groove  LMddF  assists  the  powder  in 
enlarging  the  diameter  of  the  bore.  In  addition  to  this  direct 
rupturing  strain,  the  friction  of  the  projectile  is  increased  by 
the  same  cause. 

The  slightest  inclination  of  the  bear- 
ing-surfaces from  being  truly  radial, 
causes  increased  friction,  as  at  Gr,  where 
the  pressure,  acting  in  the  line  GIT,  can 
be  resolved  into  two  forces  : GI,  useful, 
and  GK,  the  reverse. 

In  the  form  of  groove  LMUP,  the 
force  is  applied  to  the  projectile  by  the 
surface  MU  in  the  direction  IIS, 
whereas  motion  is  intended  to  be  given  fig.  150. 

in  the  direction  RT. 

750.  Advantage  of  Bounded  Angles. — The  angle  of  the  side 


248 


NAVAL  ORDNANCE  AND  GUNNERY. 


of  the  land  with  the  bottom  of  the  groove  has  the  usual  relation 
to  strength  generally  observed  in  mechanical  construction.  A 
sharp  angle  in  a part  subjected  to  strain  and  vibration  is  consid- 
ered the  beginning  of  a fracture.  For  this  reason,  Parrott  and 
others  who  understood  the  advantage  of  a radial  bearing  side, 
nevertheless  rounded  the  angle  of  their  grooves. 

Another  reason  for  rounding  the  groove,  especially  in  the 
case  of  the  Centring  System  (Art.  754),  is  to  prevent  the  vio- 
lent shock  of  the  projectile  when  its  bearing-edges  strike  the 
riliing.  Pigs.  151  and  152  are  exaggerated  to  illustrate  this. 


Fig.  152. 


The  projection  a bears  and  remains  upon  the  side  d of  the 
groove  going  in,  and  so  leaves  the  windage,  c,  on  the  other  side. 
In  going  out  the  projectile  will  have  acquired  considerable  ve- 
locity .before  it  strikes  the  side  c,  so  that  the  blow  will  be 
violent  and  the  commencement  of  the  rotation  instantaneous. 
But  the  projection  (Fig.  152)  not  only  slides  up  the  rounded 
groove  without  a blow,  but  lifts  the  projectile  into  the  centre  of 
the  bore,  thus  centring  it. 

751.  Cutting  the  Grooves. — The  practical  method  of 
cutting  the  grooves  consists  in  moving  a rod,  armed  with  a cut- 
ter, back  and  forth  in  the  bore,  and  at  the  same  time  revolving  it 
around  its  axis.  If  the  velocities  of  translation  and  rotation  be 
both  nniform,  the  grooves  will  have  a uniform  twist ; if  one  of 
the  velocities  be  variable,  the  groove  will  be  either  increasing 
or  decreasing,  depending  on  the  relative  velocities  in  the  two 
directions. 

All  the  grooves  are  first  cut  roughly  in  succession,  and  then 
finely.  The  distance  between  the  grooves  is  regulated  by  a 
disk  fastened  securely  to  the  breech  of  the  gun,  having  its  pe- 
ripheiy  equally  divided  by  as  many  notches  as  there  are  to  be 
grooves. 

The  gun  is  held  each  time  by  a pawl,  and  when  a new 
groove  has  to  be  cut,  is  turned  round  to  the  next  notch. 

The  rifling-machine  is  horizontal,  and  permanently  placed  in 
]'>osition;  the  gun  to  be  operated  upon  is  fixed  in  front  of  it.  in 
line  with  the  rifiing-bar,  which  has  a motion  of  translation  along 
its  bed  as  well  as  a certain  ainoimt  of  rotation  on  its  own  axis, 


EIFLIiSTG. 


249 


regulated  to  the  required  pitch.  An  automatic  reverse  motion 
is  contrived  for  the  bar,  so  that  when  once  set  in  motion  the 
machine  is  self-acting. 


Section  II. — Systems. 

752.  A System:  of  Hifleyg  consists  essentially  in  the 
means  of  giving  rotation  to  the  'projectile. 

The  twist  of  the  grooves,  the  length,  diameter,  or  form  of 
the  projectile,  must  depend  upon  the  purpose  for  which  a gim 
is  required,  no  matter  upon  what  system  it  may  be  rifled.  In- 
ventors often  claim  principles  which  are  as  applicable  to  one  as 
to  another  system.  As  regards  precision  of  Are,  one  system  will 
give  as  good  results,  for  all  practical  purposes,  as  another,  pro- 
vided the  conditions  of  charge,  projectile,  and  twist  of  grooves 
are  alike,  and  the  rifling  of  the  bore  and  the  manufacture  of  the 
projectiles  have  been  performed  with  the  same  amount  of  care 
and  skill  in  both  cases. 

The  conditions  that  are  especially  desirable  in  a system  of 
rising  for  ordnance  are Accuracy  of  tire,  simplicity  and  dura- 
bility in  both  projectile  and  gun,  non-liability  of  projectile  to 
jam  in  the  bore  in  loading  or  tiring.  It  must  not  cause  too 
great  strain,  and  for  heavy  ordnance,  must  allow  of  the  use  of 
large  charges. 

It  will  be  observed  that  in  many  of  the  systems  of  rifling  in 
use,  one  or  more  of  these  conditions  have  been  saeriticed  to 
some  extent,  to  secure  a closer  compliance  with  others  thought 
to  be  of  greater  importance,  or  of  easier  attainment. 

753.  Great  numbers  of  rifled  guns,  with  projectiles  to  corre- 
spond have  been  proposed,  but  most  of  the  systems  of  rifling  that 
have  been  adopted  by  any  service,  or  tried  on  the  i.'raetice- 
ground,  may  be  divided  into  the  following  classes,  each  of 
which  has  its  advantages  and  its  disadvantages,  and  none  are 
without  objections. 

First.  Muzzle  or  breech-loading  guns,  having  projectiles  of 
hard  metal,  fitting  the  peculiar  form  of  the  bore  mechanicall}^ 

Second.  Muzzle  or  breech-loading  guns,  with  projectiles 
having  soft  metal  studs  or  ribs,  to  tit  the  grooves. 

Third.  Muzzle-loading  guns,  with  projectiles,  having  a 
soft  metal  envelope  or  cup,  which  is  expanded  by  the  gas  in  the 
bore. 

Fourth.  Breech-loading  guns,  with  projectiles  having  a 
soft  metal  coating  larger  in  diameter  than  the  bore,  but  which 
is  compressed  by  the  gas  into  the  form  of  the  bore. 


250 


NAVAL  ORDNANCE  AND  GUNNERY. 


754.  First  Class. — In  this  class,  the  hard  metal  projections 
are  so  shaped  as  to  fit  the  peculiar  form  of  the  bore  mechani- 
cally. The  gaiuing-twist  is  obviously  impracticable  with  this 
form  of  lifling. 

Centring. — In  consequence  of  windage,  which  is  nece.?sary 
in  all  muzzle-loading  guns,  the  axis  of  the  projectile  does  not 
always  coincide  with  that  of  the  bore ; in  firing,  this  leads  to 
inaccuracy  of  fire. 

In  order  to  secure  accuracy  of  fire,  it  is  essential  that  the 
axis  of  the  projectile  should  correspond  with  that  of  the  bore  of 
the  gun ; for,  otherwise,  the  axis  of  rotation  will  be  variable, 
and  the  dellection  of  the  projectile  uncertain.  Should  the  axis 
of  the  projectile  on  leaving  the  bore  be  unsteady,  the  projectile 
will  have  the  'MCiUbling  motion  so  frecpiently  observed  in  ex- 
perimental pi’actice. 

A projectile  is  said  to  be  centred  when  the  grooves  of  the 
rifling  are  so  constructed  as  to  bring  the  axis  of  the  projectile 
in  line  with  that  of  the  bore  Avhen  the  piece  is  fired. 

Centring  may  embody  the  compressing  or  expanding  sys- 
tems in  any  required  degree. 

While  the  projectile  is  rotated  by  the  solid  projections 
formed  upon  it,  and  fitting  into  the  grooves  of  the  gun,  the 
exterior  of  these  projections,  or  of  the  whole  projectile,  maybe 
covered  with  a soft  substance  which  may,  in  the  case  of  a 
breech-loader,  be  largei-  than  the  bore,  and  thus  be  compressed 
while  passing  out  of  the  gun;  or  which  may  be  expanded,  by 
the  pressure  of  the  powder,  to  fill  the  gun. 

When  the  projectile  is  well  centred,  windage  cannot  afiect 
its  straight  passage  throngh  the  bore. 

Usually,  in  the  first  class,  the  hard  surface  of  the  projectile 
is  dressed  to  bear  directly  on  the  surface  of  the  bore,  leaving  a 
little  windage.  The  systems  of  Whitworth,  Y avasseur,  Scott, 
and  Lancaster  are  examples  of  this  practice. 

755.  WiiiTWOETii’s  SxsTEji. — The  Whitworth  gun  has  a 
hexagonal  spiral  bore,  the  corners  of  which  are  rounded  off. 
The  form  of  the  bore  is  not,  however,  strictly  hexagonal. 

The  interior  of  each  gun  is  first  bored  out  cylindrically, 
and  when  the  rifling  is  completed,  a small  portion  of  the 
original  cylindrical  bore  is  retained  along  the  centre  of  each 
of  the  sides  of  the  hexagonal  bore,  and  the  other  parts  of  each 
side  recede  or  incline  outw.irds  towards  the  rounded  angles ; 
hence  the  diameter  of  the  hexagonal  hore  is  greatest  at  the 
rounded  angles. 

This  description  will  be  readily  understood  by  reference  to 
Fig.  153. 


EIFLING. 


251 


The  reasons  for  thus  modifying  the  general  form  of  the 
rifling  are,  to  facilitate  loading, 
and  thus  allow  of  a reduction 
of  windage,  and  also  to  ensure, 
if  possible,  the  bearing  of  the 
sides  of  the  projectile  on  sur- 
faces instead  of  on  mere  lines, 
as  would  be  the  tendency  with 
a plain  hexagonal  bore  having 
windage. 

A hexagonal  bolt  revolved 
on  its  axis  Avithin  a slightly 
larger  hexagonal  orifice  would 
not  bear  upon  its  side,  but 
only  upon  its  six  corners.  The 
points  of  contact  Avould  be  mere  Fm.  103. 

lines. 

In  this  system,  the  bore  must  obviously  be  slightly  larger 
than  the  projectile.  In  Fig.  151,  while  the  face,  a e,  of  the  pro- 
jectile is  flat,  the  face,  d e,  of  the  bore  is  so  inclined,  that  the 


Fig.  154. 


projectile  in  coming  out  Avill  bear  upon  the  whole  of  it,  as 
shown.  If  the  face,  a e,  of  the  bore  was  also  plain,  the  projec- 
tile Avould  bear  only  on  the  corners  e 1),  etc. 

The  following  table  gives  the  particulars  of  the  Whitworth 
guns  and  rifling ; 


252 


NAVAL  ORDNANCE  AND  GUNNERY. 


!.a 


-g- 


t5rd 

C 

O ti) 

^ a 

• o 

.S 

^.a 


c ^5  to 


Ch  O 

CO  CO 
CJ  o 

£h  H 


. o 

o ^ 

c.  S 


The  peculiarities  of  this  system  are  the  polygonal  rifling  and 
comparatively  small  bore.  It  has  great  range  and  penetration, 
bnt  has  never  been  adopted  for  heavy  gnns  by  any  nation  ex- 
cept Brazil. 

The  polygon  has  twenty-four  surfaces  with  six  grooves,  each 
.4  inch  deep. 

Though  the  long  iron  bearing  diffuses  the  strain  over  a large 
surface,  and  enables  a rapid  twist  with  great  rotation  to  be 


RIFLING. 


253 


V f5}. 


fcl) 

S 


o 


g 

cj 

& 


o' 


"SiwWtofcCs.V^.-i.IiaA. 


254 


NAVAL  ORDNANCE  AND  GUNNERY. 


given,  yet  the  hearing  is  really  on  a mere  line  in  each  groove, 
and  is  ninch  nearer  the  axis  of  the  projectile  than  in  systems 
with  projecting  flanges,  and  tlie  leverage  for  rotating  is  there- 
fore much  less. 

In  muzzle-loading  gnns  of  this  system  it  is  difficult  to  thor- 
oughly sponge  the  bore. 

A patent  lubricating  cartridge  in  a metallic  case  is  used  with 
the  breech-loaders. 

756.  Yavasseue’s  System. — This  method  comes  under  the 
head  of  rih-rijling  (Art.  729) — the  rotation  being  given  by 
means  of  raised  ribs  in  the  bore,  while  the  projectile  itself  has 
corresponding  grooves  cut  along  its  cylindrical  surface. 

The  ribs  are  three  in  number ; their  shape,  and  also  that  of 


the  coiTesponding  grooves,  are  shown  in  Fig.  156.  There  are 
no  sharp  angles  either  in  the  projectile  or  the  bore  of  the 
piece. 

The  dimensions  and  particulars  concerning  the  guns  and 
rifling  are  given  in  the  following  tables : 


RIFLING, 


255 


The  twist  of  the  rifling  is  one  turn  in  thirty  calibres  for  all 
sizes.  The  angle  of  the  twist  is  5°,  58',  41'h6,  and  is  thus 
obtained : 

In  the  light-angled  triangle  ABC  (Fig.  157),  let  AB  = n = 
the  number  of  calibres  in  which  the  projectile  makes  one  revo- 
lution = 30  = 

BC  = circumference  of  bore, 
d = angle  of  rifling ; 


256 


NAVAL  ORDNANCE  ziND  GUNNERY. 


Then  tan  0 = 

Ali 


7T 

11 


3.1416 

30 


nat.no.  0.10472  log  9.020029  = 5°.58',  41A6. 


Fio.  157. 


To  find  the  Width  of  Tib. — Having  width  of  rib  for  one  ^nn, 

to  hnd  that  of  another 
gun,  when  r'  of  the  latter 
is  known, 
w'  — width  of  i-ib. 
v'  = diam.  inside  of 
rib  (col.  e.  of  Tab). 
1.5  = width  of  rib  of  12- 
in.  gun. 

5.7  — r'  for  12-in.  gun. 
Then  w' ; 1.5  = r' : 5.7. 
Suppose  w'  is  required 
for  10-in.  gun,  when 
r'  = 4".75, 

w'  = r'  X ^ - .263r' 
5.1 

= .263  X 4.75  == 
Fig.  158.  1".  24925,  or  l'b25  (col.  e 

of  Table). 

In  this  system  the  bore  of  the  gun  is  not  weakened  by  hav- 
ing grooves  cut  into  it,  and  the  projectile  is  also  considerably 
stronger  than  those  fitted  with  studs,  because  the  metal  cut  out 
of  the  body  of  a tivelve-iuch  projectile,  for  instance,  by  the  coun- 
tersinks for  fixing  the  stucls  (Art.  782),  is  more  than  that  cut 
out  of  the  same  projectile  by  the  three  grooves. 

There  is  also  considerable  less  scoring  in  the  bore,  as  the 
part  most  aHected  by  the  rush  of  the  gas  in  the  part  between 
tlie  ribs,  nearly  one-third  the  whole  circumference  in  width ; 
the  scoring  is,  therefore,  much  less  local  and  takes  place  in  a 
part  not  weakened  by  grooves  cut  into  it,  as  is  the  case  in 
grooved  guns,  where  the  grooves  being  the  highest  part  of 
tlie  bore  act  as  channels  along  which  the  gas  rushes. 

It  is  claimed  that  as  the  ribs  in  this  system  project  froin  the 


RIFLING. 


257 


surface  of  the  bore,  they  are  mucli  more  effectnany  cleaned 
than  are  grooves,  by  sponging,  so  that  much  less  windage 
can  be  allowed. 

Late  experiments  to  determine  the  relative  values  of  long 
and  of  short  rifle-bearuigs  have  demonstrated  the  great  superior- 
ity of  the  system. 

This  arrangement  necessarily  involves  a considerable  amount 
of  friction,  the  more  so  as  both  the  metals  which  come  into  con- 
tact are  hard.  It  is  necessaiy  that  the  projectiles  should  be 
fitted  with  peculiar  precision,  .so  as  to  preclude  jamming  on  the 
one  hand,  and  too  much  windage  on  the  other. 

757.  Scott’s  Sys- 
tem.— In  this  method  | 

the  bore  is  rifled  with  i 

narrow,  s h a 1 1 o w 
grooves  (Fig.  159), 
deeper  on  the  driving 
than  on  the  loading 
side.  The  projectile 
is  one  iron 

ribs  almost 


casting 

having 
triangular  in  section, 
extending  the  whole 
length  of  the 


the  drivin2;-side. 

O 


cylin- 
drical body,  and  set 
to  the  angle  of  the 
rifling.  In  cross  sec- 
tion the  ribs  give  a 
deep  bearins’-surface 
on 

(Fig.  160.) 

By  shallowing  the  loading-side  of  the  groove,  the  ribs  rest 
on  inclined  planes  so  that  the  projectile,  when  forced  into  its 
seat,  has  a natural  tendency  to  slip 
round  so  as  to  cling  to  the  driving- 
side  before  the  mm  is  fired,  to  start 
easily,  and  to  mount  into  the  centring 
position  the  moment  it  begins  to  move 
out. 

Less  windage  is  given  to  the  ribs 
on  the  jirojectile  than  to  its  body,  so 
that  it  rests  upon  its  projections,  and 
its  body  does  not  touch  the  bore  at  all. 

The  ribs  almost  till  up  the  grooves,  and  check  the  escape  of 
the  gas,  with  its  consecjuent  erosion  of  the  bore,  and  unecj^ual 
17 


258 


NAVAL  ORDNANCE  AND  GirNNT:E,T. 


action  on  the  projectile.  While  hy  striking  the  curve  of  the 
cross  section  of  the  groove  and  of  the  rib  with  two  different 
radii,  the  latter  is  driven  up  into  the  centre  of  the  bore  at 
once,  causing  the  axis  of  the  projectile  and  of  the  bore  to  coin- 
cide. (Fig.  161.) 


In  this  system  there  are  3 grooves  for  9-ton  guns  and  un- 
der; 5 grooves  for  12  and  IS-tnn  guns;  and  7 grooves  for  25- 
ton  guns  and  upwards.  The  grooves  are  of  the  same  size  for 
all  guns.  lYidth,  0.8  inch ; depth,  0.125  inch.  This  system 
has  not,  as  yet,  been  generally  adopted  by  any  nation. 

758.  Lancaster’s  Systew. — This  method  may  be  described 
as  that  of  the  usual  circular  bore  with  two  wide  grooves,  each 

about  one-third  the  circumfer- 
ence in  width,  the  shoulders  of 


the  grooves  being  shaved  off  so 
as  form  an  ellipse.  (Fig.  1G2.) 
Tlie  cross  section  of  tlie  bore  is 
oval,  only  a trace  of  the  ongiual 
bore  being  left  at  the  minor 
axis. 

The  absence  of  shoulders  to 
the  two  grooves  converts  the 
two  places  of  contact  of  the 
jarojectile  with  the  rifling,  into 
circular  wedges  tending  to  burst 
the  gun  or  to  compress  the  pro- 
jectile. 

This  system  has  much  to 
commend  it,  on  account  of  its  simplicity,  but  it  has  never 
obtained  success ; on  the  contrary,  it  has  been  very  unsuccess- 
ful in  competition  with  other  systems. 

759.  CV»n>AKATiVE  Advantages  of  the  First  Cl.vss  — 
, The  advantages  of  this  class  are  : economy,  simplicity,  and  d’u- 
ahility  of  p.'ojectile.  The  rilie-motion  is  communicated  with 
great  certainty  and  regularity.  The  projectile  does  not  expand 


Fiff.  103. — Lancaster’s  Riflino 


RIFLING. 


259 


Aviuclage 
the  c 


as 


as  the  here 
Jims  expands 


by  the  explosion,  and  hence  get's  more 
warms,  so  that  its  safety-valve  gets  larger 
and  gets  weaker. 

The  chief  objections  are,  that  hotli  projectile  and  bore  being 
hard,  fracture  of  one  or  the  other  is  liable  to  oeenr  from  a pro- 
jectile and  that  unless  the  bore  be  made  of  very  hard 

material,  it  will  be  rapidly  worn  by  the  friction  of  the  projec- 
tile on  it. 

The  obvious  mechanical  advantages  of  the  Gentrinfj  System 
recommend  it.  It  decreases  the  strain  upon  the  gim  by  allow- 
ing windage  without  affecting  the  accuracy  of  the  flight  of  the 
projectile ; and  when  so  applied  as  to  bring  the  minimum  wedg- 
ing-strain  and  friction  upon  the  gun,  and  to  place  and  hold  the 
projectile  in  the  centre  of  the  bore  without  shock,  and  to  allow 
its  centre  of  gravity  to  be  in  the  centre  of  figure,  and  to  sup- 
port the  projectile  at  or  on  both  sides. of  its  centre  of  gravity, 
thus  promoting  velocity  and  accuracy,  it  woidd  seem  that  this 
system  must  be  the  best  to  be  adopted  for  heavy  ordnance. 

760.  Second  Class. — In  this  class  the  body  of  the  projectile 
is  composed  of  a hard  metal,  as  cast-iron,  and  there  are  attached 
to  it  projections  of  soft  metal  in  the  form  of  ribs,  or  rounded 
buttons  so  arranged  as  to  enter  the  grooves  of  the  rifling.  The 
Woolwich  or  French  rifling,  and  the  Shunt  system  are  exam- 


— The  present  English  service 
It  is  a modification  of  the 


deep  broad  grooves  (Fig.  163), 


pies  of  this  class. 

761.  The  Woolwich  System. 
rifling  is  called  by  this  name. 

French  System,  and  consists  of 
each  of  which  receives 
two  soft  metal  circular 
studs  attached  to  the  pro- 
jectile. 

The  grooves  are  three 
or  more  in  number,  ac- 
cording to  the  calibre  of 
the  piece ; they  are  1.5 
inches  wide,  and  0.18 
inches  deep,  with  curved 
edges,  both  the  loading 
and  driving  edg 

bottom  of  the  grooves  is  eccentric  to 
with  a radius  of  3 inches ; they  are  of 
natures  of  heavy  guns,  but  are  a little 

gun  and  upwards ; the  grooves  are  also  widened  at  the  muzzle 
in  the  larger  guns,  in  order  to  faciliate  lc>ading  by  cutting  away 
the  loading  side  slightly  for  two  inches  from  the  muzzle. 


being  struck  with 


the 
the 
the 
deeper 


same  radius.  The 
bore,  being  struck 
same  width  for  all 
for  the  10-inch 


260 


NAVAL  ORDNANCE  AND  GUNNERY. 


This  system  embraces  imiform  and  increasing  twists,  the 
latter  being  preferred. 

Both  the  direction  and  twist  are  given  by  the  bearing  of  the 
studs  on  the  grooves,  the  body  of  the  projectile  never  being  in- 
tended to  come  into  contact  with  the  bore.  The  windage  is  0.8 
inch  in  all  calibres. 

The  projectiles  have  two  studs  for  each  groove  in  all  in- 
stances ; both  studs  in  the  case  of  the  uniform  twist,  and  the 
rear  one  where  tlie  twist  is  increasing,  are  nearly  of  the  size 
of  the  groove,  with  their  faces  corresponding  to  the  curved  bot- 
tom of  the  groove. 

The  rear  stud  is  four  inches  from  the  bottom  of  the  pro- 
jectile, and  the  studs  of  each  groove  are  ecjuidistant  from  the 
centre  of  gravity.  (Art.  783.) 

Particulars  of  the  Riflincj : 

12-inch  gun,  9 grooves ; twist  increasing  from  1 in  100  to 
1 in  50  calibres  at  muzzle.  10-inch  gun,  7 grooves;  twist  in- 
creasing from  1 in  100  to  1 in  40  calibres  at  muzzle.  9-inch  gun, 
6 grooves  ; twist  increasing  from  0 to  1 in  45  calibres  at  muz- 
zle. 8-inch  gun,  4 grooves  ; twist  inci’easing  from  0 to  1 in  40 
calibres  at  muzzle.  7-inch  gun,  3 grooves ; twist  uniform  1 
in  35  calibres. 

The  7-inch  gun  has  a uniform  twist  because,  at  the  time  of 
its  introduction,  the  uniform  was  preferred  to  the  increasing 
spiral. 

762.  The  Shunt  Systew. — This  is  one  of  Armstrong's 
systems  of  rifling.  The  peciiliarity  of  this  system  is  that  the 
depth  and  width  of  the  grooves  vary  at  dilierent  parts,  the  ob- 
ject aimed  at  being  to  provide  a deep  groove  for  the  studs  of 
the  projectile  to  travel  down  when  tlie  gun  is  being  loaded, 
and  a shallow  groov^e  through  which  they  must  pass  when  the 
gun  is  fired,  so  that  the  projectile  may  be  gripped  and  perfectly 
centred  on  leaving  the  muzzle.  This  is  obtained  by  making 
pne  side  of  the  groove  (the  driving-side)  near  the  muzzle,  shal- 
low, as  shown  in  Fig.  164,  the  unshaded  j)ortion  representing 
the  shallow  part,  or  grip. 

The  projectiles  have  soft  copper  studs,  which  fit  easily  with 
a windage  of  0.025  inch  into  the  deep  portion  of  the  groove ; 
when  the  gun  is  loaded,  the  studs  travel  down  this  deep  portion 
until  they  reach  about  the  middle  of  the  bore,  where  they  meet 
with  an  incline,  by  which  they  are  ‘‘  shunted,”  or  switched  off, 
into  a narrow  part  of  the  groove,  still  of  the  same  depth, 
down  which  they  travel  to  the  chamber. 

On  discharge  the  studs  bear  against  the  other  side  of  the 
groove,  until  they  come  to  the  incline,  up  which  they  travel, 


RIFLING. 


261 


the  studs  being  thereby  compressed.  With  this  compression 
they  pass  through  the  remaining  part  of  the  bore. 


7(fl 


Fig.  164. 


There  are  three  grooves  with  a uniform  pitch  of  one  turn 
in  4-0  calibres,  the  edges  being  angular. 

This  system  was  introduced  with  certain  guns  of  the  Arm- 
strong pattern  in  the  English  service,  after  the  repeated  fail- 
ures of  his  heavy  breech-loading  guns,  because,  it  carried 
out  two  favorite  theories  of  Sir  William  Armstrong,  viz.,  the 
centring  of  the  projectile  and  its  retardation.  The  last  is 
now  generally  conceded  to  be  a disadvantage.  It  has  been 
abandoned,  because  it  was  not  found  to  answer  well  in  prac- 
tice. 

It  was  complicated  ; the  projectile  was  gripped  at  the  muzzle 
when  at  its  highest  velocity,  thus  greatly  straining  the  piece, 
and  the  sharp  angles  at  the  edge  of  the  grooves  rendered  the 
tube  liable  to  split. 

763.  CoMPAKATivE  Advaisttages  of  the  Second  Class. — 
In  this  class  the  studs  being  soft,  the  bore  is  not  liable  to  in- 
jury from  the  projectile,  if,  as  should  always  be  the  case,  the 
height  of  the  stud  is  rather  greater  than  the  depth  of  the 
groove,  so  that  the  projectile  moves  through  the  bore  on  the 
studs  alone.  Also  if  a jam  should  occm’,  the  studs  will  give 
away,  and  so  prevent  injury. 


262 


NAVAL  ORDNANCE  AND  GUNNERY. 


Studs  in  tlie  middle  of  the  projectile  instead  of  long  hear- 
ings on  its  cylindrical  portion,  or  expanding  material  at  its 
base,  allow  tlie  rifling  to  stop  farther  away  from  the  chamber ; 
so  that  the  gun  is  not  weakened  by  it,  at  the  point  of  greatest 
powder-pressnre. 

On  the  other  hand,  the  studs  cause  additional  expense  in 
mannfactnre,  and  they  are  liable  to  injnry  in  transport  or  store. 
And  the}"  are  a frecpieiit  canse  of  injnry  to  the  bore  from  over- 
riding the  grooves. 

76-f.  Third  Class.- — In  this  class  the  body  of  the  projectile 
is  composed  of  a hard  metal,  and  there  is  attached  to  it,  gener- 
ally at  the  base,  a cup,  band,  or  other  arrangement  of  soft 
metal,  by  the  expansion  of  which  into  the  grooves  of  the  gim 
the  projectile  is  given  rotation. 

The  expansion  system  is  carried  out  on  the  most  extensive 
scale  in  this  country.  The  plan  of  rifling  which  has  heretofore 
been  almost  nniversally  adopted  in  the  United  States  consists 
of  lands  and  grooves  of  the  same  or  nearly  ecpial  width.  As 
the  standard  Army  and  Navy  projectiles  are  of  the  expanding 
class,  they  may  all  be  used  in  any  gnu  of  the  proper  calibre, 
irrespective  of  the  width  or  depth  of  the  gi-oove. 

The  Parrott,  Hotchkiss,  and  Shenkle,  and  many  other 
jirojectiles,  belong  to  this  class.  The  Parrott  system  will  illus- 
trate it.  (Art.  TSo.) 

105.  Tue  Par- 
rott System. — In  the 
rifling  of  the  Parrott 
guns  the  grooves  and 
lands  are  of  equal 
width,  the  former  be- 
ing one-tenth  inch 
deep  for  all  calibres. 
The  bottom  corners 
of  the  grooves  are 
rounded  to  facilitate 
cleaning  and  to  do 
away  with  the  me- 
chanical disadvantage 
of  a sharp  corner. 
(Fig.  165.)  , 

The  jwojectiles  are 
recessed  around  the 
corner  of  the  base  to 
receive  a brass  ring  which  is  expanded  into  the  grooves  of  the 
gun  by  the  explosion  of  the  powder. 


RIFLING. 


263 


All  calibres  are  rifled  with  an  increasing-twist. 

The  following  table  gives  the  particulars  of  the  Parrott 
guns  and  lifling. 

The  calibres  in  use  in  the  naval  service  are  the  100-pdr.  and 
the  60-pdr. 

The  30-pdrs.  and  20-pdrs.  have  been  withdrawn,  and  a new 
bronze  20-pdr.  rifle  substituted. 

Pound  shot  can  readily  lie  used  in  these  guns  when  advan- 
tageous, as  for  the  ricochet.  They  should  be  wrapped  in  canvas 
or  other  suitable  material,  with  the  object  of  bringing  their 
centre  as  nearly  in  the  axis  of  the  bore  as  practicable. 


PARTICULARS  AND  A3LMUNITION  OF  TFIE  PARROTT  GNNS. 


NA5IE  OP  GUN. 

Length  of  Boro. 

Diameter  of  Bore.  | 
1 

Diameter  over 
lleinforce. 

-fcS 

No.  of  Grooves. 

1 Depth  of  Grooves.  | 

-- 
cb 
^ -3 

o 

'o  o 
"k  m 

H 

Charge.  1 

U 

‘o' 

% 

^ A 

o 

1 turn 

Ins. 

Ins. 

Ins. 

Lbs. 

Ins. 

in  ft.  ut 

Lbs. 

Lhs. 

mu'zzie. 

1 

1 Shot,  lOl  p 

lO-pdr 

70 

3 

11.3 

890 

o 

o 

1 0 

10 

1 

■(  Shed,  9f  i 

20-pdr 

79 

3.67 

14.5 

1750 

5 

1 

1 u 

10 

2 

j Shot,  194  ) 

( Shell,  18|  y 

30-pdr.  Army. 

120 

4.20 

18.3 

4200 

1 

12 

3J 

30-pdr.'  Navy. 

96.8 

4.20 

18.3 

3550 

60-pdr.  Navy. 

105 

5.3 

21.3 

5360 

7 

1 

15 

6 

55 

100-pclr 

130 

6.4 

25.9 

9700 

9 

V 

18 

10 

70  to  ICO 

8-inch 

136 

8 

32 

1C300 

11 

1-U 

23 

16 

132  to  175 

10-inch 

144 

10 

40 

26500 

15 

1 

1 0 

30 

25 

230  to  250 

766.  Comparative  Advaxtages  of  Third  Class. — Ex- 
panding projectiles  cannot  be  tired  with  as  heavy  a charge  of 
powder  as  others,  for  fear  of  breaking,  nor  are  they  ajwa^-s 
sure  to  receive  the  rifle-motion.  The  windage  being  greatly 
reduced  or  entii’ely  stopped,  the  strain  on  the  gun  is  increased,, 
and  an  ordinary  time-fuze  will  not  always  be  lighted  by  the 
flame  from  the  charge  of  the  gun.  Fragments  of  the  expand- 
ing attachment  are  liable  to  fly  otf  and  injure  those  in  advance. 
The  centre  of  gravity  is  almost  necessarily  behind  the  centre 


264 


NAVAL  OEDNANCE  AND  GUNNEKY. 


of  figure,  and  the  bearing  of  the  projectile  is  usually  behind 
the  centre  of  gravity. 

767.  Foukth  Class. — With  this  class  the  projectile  is 
larger  than  the  bore,  and  is  squeezed  or  planed  to  fit  the  V)ore 
b}^  the  lands  of  the  rifiing.  The  projectile,  therefore,  must 
have  a soft  coating,  and  be  entered  at  the  breech  into  a cham- 
ber larger  than  the  rest  of  the  bore ; and  whatever  escape  of 
gas  there  may  be  around  the  breech-closing  apparatus  reduces 
its  range  and  velocity. 

This  plan  was  early  adopted  and  perfected  by  the  Germans, 
wdio  obtained  great  accuracy  and  range  with  charges  of  one- 
ten  tli  weight  of  the  projectile.  The  rifling  consisted  of 
numerous  shallow  rectangular  grooves. 

The  Armstrong  system  of  rifling  for  breech-loaders  for- 
merly used  in  the  Englisli  service  does  not  differ  in  principle 
from  this.  The  rifling  consists  of  a great  number  of  shallow, 
narrow  grooves  (the  7-inch  has  76),  the  object  being  to  give  the 
soft  metal  coverino;  a verv  larve  bearino-  on  the  drivin»;-side  of 
the  grooves,  and  thus  prevent  stripping,  and  make  up  for  want 
of  depth.  This  system  has  been  abandoned. 

The  German  system  will  illnstrate  this-class. 

768.  The  Geioian  Systew,  or  Krupp's  Method. — In  this 
system  the  grooves  are  thirty  in  number  for  all  calibres,  quite 
shallow,  and  of  the  form  shown  in  Fig.  166,  their  sides  being 
rachal  and  forming  sharp  angles  with  the  bore.  The  rifling 
has  a uniform-twist  of  one  turn  in  25  feet. 

The  grooves  are  wider  at  the  bottom  of  the  bore  than  at  the 
muzzle,  so  that  the  compression  of  the  lead-coated  projectile  is 
gradual,  and  less  force  is  expended  in  changing  the  shape  of 
the  projectile. 

This  change  of  shape  is  effected  by  making  the  whole 
groove  of  the  same  size  as  at  the  muzzle,  and  then  cutting  away 
gradually  on  the  loading-edge  of  the  groove.  Of  course,  as 
the  twist  is  uniform,  the  driving-side  of  the  groove  cannot  vary. 

Tim  outer  surface  of  the  lead  coating  of  the  projectile  is  in 
naised  rings  with  grooves  between,  to  allow  space  for  its  being 
drawn  down  in  passing  through  the  bore.  (Fig.  182.) 

769.  Comparative  Advantages  of  the  Fourth  Class. — The 
compressing  system  unduly  strains  the  gun  by  suddenly  stop- 
ping windage,  by  fouling,  and  b}’'  forcing  the  projectile  into  a 
bore  of  smaller  diameter.  The  compressed  projectile  must  be 
fired  from  a breech-loading  gun,  and  the  increasing-twist  is  im- 
practicable from  the  great  length  of  the  soft-metal  bearing. 
Tlie  soft  coating  of  the  projectile  is  liable  to  injury  in  handhug 
and  in  store;  also  to  be  stripped  on  firing. 


RIFLING. 


265 


Its  adv'antages  are  that  the  projectile  is  centred  during  its 
passage  through  the  bore,  which  prevents  balloting ; the  angles 
of  departure  and  the  initial  velocities  are  therefore  more  uni- 


A 


form,  and  the  stability  of  the  axis  of  rotation  on  leaving  the 
bore  is  better  assured  ; from  w'hich  result  great  regularity  and 
precision  of  tire.  There  is  little  or  no  ditficulty  as  to  erosion 
of  the  metal  caused  by  the  gas  forcing  its  way  between  the  pro- 
jectile and  the  bore. 

The  lead  jacket  of  the  forced  projectile  does  not  prevent 
the  employment  of  heavy  charges.  Forced  projectiles  do  not 
wedge  in  the  bore.  The  regularity  of  the  movement  of  these 
projectiles  does  not  wear  or  injure  the  bore.  The  soft-metal 
coating  prevents  damage  to  the  lands. 

The  bursting  of  a projectile  covered  with  soft  metal  has 
comparatively  no  baneful  etfect  on  the  gun. 

770.  BliElfCH-LOADIlSlG. — Intimately  connected  with 
the  subject  of  the  different  systems  of  rifling  is  that  of  the  ad- 


2G6 


NAVAL  ORDNANCE  AND  GUNNERY. 


vantages  and  disadvantages  of  Ijreech-loading  for  cannon. 
There  are  strong  arguments  both  for  and  against  tlie  use  of  the 
breeehdoaders — some  nations  using  them  altogether  and  others 
not  at  all. 

771.  Advantages. — A principal  advantage  claimed  for 
breech-loading  guns  is  rapidity  of  tire,  bnt  the  result  does  not 
seem  to  have  been  attained  in  the  large  guns. 

The  gun  can  be  loaded  when  run  out,  without  exposing  the 
men,  and  worked  in  a smaller  space  by  limiting  the  recoil. 
Any  ignited  substance  left  in  the  bore  can  be  seen  and 
removed ; and  there  is  no  danger  of  the  projectile  not  being 
home. 

The  breech-loading  gun  may  be  made  longer,  occasionally, 
which  is  a great  advantage  Avhere  there  is  difficulty  in  burning 
the  powder;  moreover,  a large  powder-chamber  may  be  em- 
ployed for  the  better  burning  of  the  charge. 

The  advantages  of  the  I'ourth  Class  of  Eifiing  (Art.  769) 
may  be  claimed  in  favor  of  breech-loading. 

772.  Disadvantages. — The  breech-loading  cannon  is  heavier 
and  more  expensive  than  one  loading  at  the  muzzle. 

There  are  more  parts  to  be  damaged.  In  heavy  guns,  far 
from  there  being  any  increased  facility  in  loading,  considerable 
force  has  to  be  used  and  applied  in  a very  careful  way  to  the 
breech-closing  apparatus,  or  the  gun  may  be  rendered  tempora- 
rily unserviceable.  Escape  of  gas,  fouling  or  corrosion  of  the 
closing  surfaces,  and  injury  to  the  delicate  Broadwell-riug  or 
gas-check,  are  among  the  contingencies  that  may  arise  in  ser- 
vice. 

Much  additional  labor  and  outlay  are  required  to  construct 
and  tit  up  interchangeable  hollow  screws  or  sliding  stoppers; 
to  fit  and  renew  gas-checks;  to  apply  opening  and  closing 
apparatus,  which  cannot  be  very  simple,  but  which  must  be 
very  strong  and  durable;  to  fabricate,  keep  clean,  and  main- 
tain all  these  parts  on  such  a plan  that  two  or  three  men  can 
manipulate  them  with  ease  and  certainty,  and  without  unusual 
risk  of  disaster  from  excitement  or  carelessness ; and  of  such 
size  and  strength  that  the  heaviest  projectiles  can  be  fired,  with 
large  charges  of  powder. 

' 773.  Conclusions.- — The  adoption  of  a system  of  working 

and  loading  guns  by  hydraulic  power  (Art.  SS6)must  have 
an  important  bearing  upon  the  question  of  the  comparative 
merits  of  breech  and  muzzle  loaders.  One  of  the  chief  advan- 
tages claimed  for  breech-loaders  is  that  any  length  of  bore 
can  be  adopted  without  increasing  the  difficidty  of  loading, 
and  that,  therefore,  a higher  duty  can  be  obtained  from  the 


RIFLING. 


267 


powder.  It  lias  also  been  urged  that  a gun  of  larger  size  can 
be  worked  in  a given  turret  as  a breecli-loader.  Successful 
niecbauical  methods  for  loading  at  the  muzzle  would  seem 
to  negative  these  advantages. 

The  suppression  of  wdndage  and  the  power  of  placing 
the  vent  in  the  breech-block  are  important  advantages  claimed 
for  hreeclidoaders.  It  has  now  become  very  important  to 
suppress  windage,  which  tends  much  more  rapidly  to  score 
and  cut  up  the  bore  in  very  heavy  guns,  tired  with  large 
charges  of  slow  burning  powder,  than  in  small  guns  tired  with 
light,  quick-burning  charges.  Tlie  vent  is  also  a serious 
trouble  in  A*ery  heavy  guns,  from  its  rapid  erosion  by  the 
same  cause.  But  it  is  claimed  that  the  windage  can  be  etfect- 
ually  suppressed  in  many  muzzledoading  systems  of  rifling 
and  projectiles,  and  an  arrangement  lias  been  devised  for  stop- 
ping altogether  the  passage  of  gas  through  the  vent,  thus 
removing  the  difliculty  of  its  erosion.''^ 

In  view  of  these  facts,  the  relative  merits  of  the  two 
systems  must  remain  undetermined  fof  the  present. 


* lu  some  experiments  made  in  England  by  Capt.  Noble  upon  the  force 
of  fired  gunpowder,  be  succeeded  in  effectually  closing  the  vent,  as  follows  ; 
The  stoppage  of  the  vent  was  effected  by  an  apparatus  consisting  of  a steel 
plug  screwed  into  the  body  of  the  gun.  immediately  over  the  copper  vent. 
This  remained  a fixture,  but  was  capable  of  easy  removal  in  case  it  should 
he  desirable  to  fire  by  the  ordinary  process.  The  interior  of  the  plug  was 
bored  out  and  screwed,  so  that  another  plug  could  be  fitted  inside  of  it. 
The  inner  plug  had  half  the  thread  cut  away  as  in  the  screw  of  the  French 
breech-loading  gun,  so  that  it  went  in  at  once  and  by  a quarter  of  a turn  was 
rendered  fast.  Inside  of  the  iimer  plug  a little  plunger  worked  in  a cylindri- 
cal chamber,  into  which  a primer  representing  the  common  friction-rube 
was  dropped.  In  the  centre  of  the  plunger,  there  was  a pin  to  fire  the 
primer  by  detonation,  and  surrounding  it  a steel  gas-check,  which,  when  the 
powder  was  exploded,  expanded  so  as  to  stop  the  escape  of  gas.  The  charge 
was  fired  by  striking  the  external  head  of  the  plunger.  The  recoil  of  the 
plunger  was  stopped  by  a shoulder. 


CHAPTEE  VI. 


PROJECTILES. 

Section  I. — General  Descrijytion. 

774.  Classieication. — Projectiles  may  be  classified — accord- 
ing to  their  form,  as  spherical  and  elongated  ; according  to  their 
structure  and  mode  of  operation,  as  solid^  holloio,  and  case  shot. 

775.  SPIIEEICAL  PEOJECTILES. — Spheiical  projec- 
tiles are  commonly  nsed  in  smooth-bore-gnns,  and  for  tbis  pur- 
pose possess  certain  advantages  over  those  of  an  elongated  form. 
1st,  they  present  a uniform  surface  to  the  resistance  of  the  air 
as  they  turn  over  in  their  flight;  2d,  for  a given  weight  they 
offer  tiie  least  extent  of  surface  to  the  resistance  of  the  air ; 3d, 
the  centres  of  figure  and  inertia  coincide ; 4th,  they  touch  the 
surface  of  the  bore  at  only  one  point ; they  are  therefore  less 
liable  to  wedge  in  the  bore  and  endanger  the  safety  of  the 
piece.  5th,  their  rebound  on  land  and  water  being  certain  and 
regular  thev  are  Avell  suited  to  ricochet-firing. 

77G.  ELONGATED  PEOJECTILES.— The  great  im- 
provements Avhich  have  been  made  of  late,  in  the  accuracy  and 
range  of  cannon,  consist  simply  in  the  use  of  the  elongated  in- 
stead of  the  spherical  form  of  projectile. 

To  attain  accuracy  of  flight  and  increase  of  range  with  an 
elongated  projectile,  it  is  necessary  that  it  should  move  through 
the  air  in  the  direction  of  its  length.  Experience  seems  to 
show  that  the  only  sure  method  of  affecting  this  is  to  give  it  a 
rapid  rotary  motion  around  its  long  axis  by  the  grooves  of  the 
rifles. 

777.  Length. — This  necessaiily  varies  in  the  different  de- 
scriptions of  j)i’ojectiles  for  the  same  gun,  inasmuch  as  it  is  to 
some  extent  subordinate  to  the  consideration  of  bringing  them 
all,  with  certain  exceptions,  to  the  same  weight ; but  experiments 
go  to  prove  that  a length  of  two  calibres  at  least  is  necessary 
for  very  accurate  firing,  and  it  is  desirable  for  good  “ vis  viva,'’ 
or  destructive  effec-t  on  impact  at  any  but  very  short  ranges,  to 
have  the  weight  great  in  proportion  to  the  calibre,  or,  in  fact,  to 
the  surface  of  resistance,  and  of  course  this  is  favored  by  an  in- 
creased length  of  projectile.  As  a rule,  the  best  length  for 


PEOJECTILES. 


269 


accurate  firing  with  any  ordinary  twist,  has  been  found  to  he 
from  two  to  three  calibres. 

778.  Form  of  Head. — The  form  of  head  is  governed  by 
two  considerations,  flight  and  penetration.  The  latter  gives 
difierent  forms  in  different  instances.  (Art.  851.)  The  question 
of  flight  affects  all  equally,  and  on  this  many  experiments 
have  been  made,  which  have  resulted  in  the  general  adop- 
tion of  wliat  is  termed  an  ogival  head,  or  figure  generated 
by  the  revolution  of  an  ogival,  or  pointed  arch,  about  its  axis. 

It  has  been  found  that  the  total  pressure  on  a nine-inch 
spherical  projectile,  moving  with  a velocity  of  1150  feet  per 
second,  is  about  555  lbs.  AHBM  representing  the  spherical 
nine-inch  pi'ojec- 


same  diameter  rep-  ^ 

resented  by  AC.D  Fig.  167. 

BM,  and  moving 

with  the  same  velocity,  is  -187  lbs. — ^^thus  showing  a difference 
of  681bs.  total  pressure.* 

How  supposing  the  elongated  projectile  to  move  steadily, 
point  first,  the  pressure'  on  the  respective  heads,  AMB,  must 
be  the  same ; therefore  the  difference  of  the  total  pressure, 
viz.,  681bs.,  must  be  due  to  the  difference  of  minus  pressure 
on  the  bases  AHB,  ACDB  respectively,  thus  showing  that  the 
form  of  base  of  a projectile,  materially  influences  the  total  pres- 
sure which  it  meets  with,  when  moving  through  the  air  at  a 
high  velocity. 

The  total  pressure  on  an  ordinary  ogival-headed  projectile 
of  nine-inch  diameter,  represented  by  ACDBM',  is  only 
3891bs'.,  thus  showing  the  great  difference  of  pressure,  viz., 
1661bs.,  on  an  elongated  ogival-headed  projectile  and  a spheri- 
cal projectile  of  the  same  diameter  when  moving  at  the  same 
velocity  through  the  air.  Another  great  advantage  which  the 
elongated  projectile  possesses  over  the  spherical,  is  that,  for  the 
same  calibre,  the  momentum  of  the  former  is  much  greater, 
varying,  of  course,  in  proportion  to  their  respective  weights, 
which  would  be  nearly  three  to  one,  depending  on  the  length 
of  the  elongated  projectile. 

779.  The  construction  of  ogival  heads  of  radii  of  1, and  1|- 
diameter  respectively,  may  be  seen  in  Figs.  168,  169,  and  170 — 


tile  (Fig.  167),  and  _ 


the  total  pressure 
on  a hemispherical-  ^ 
headed,  elongated 


projectile  of  the 


* Bashforth. 


270 


NAVAL  ORDNANCE  AND  GUNNERY. 


C and  C'  being  tlic  centres  and  K the  length  of  the  radii  in 


each  case.  It  ■whl  be  seen  in  the  case  of  diameters  radius 
that  the  head  is  exactly  1 calibi'e  long. 

780.  hiewton  gives  the  form  of  body 
(Fig.  171)  whicli  vould,  in  passing 
through  a tlnid,  experience  the  least  resist- 
ance. This  form,  it  is  seen,  is  very  simi- 
lar to  the  ogival. 

781.  Piobert  says  that  the  figure 
(172)  will  experience  the  least  resistance 

fiom  the  air.  Its  lengrh  is  five  times  its  greatest  diameter,  and 
its  largest  section  is  placed  of  the  length  from  the  hind  part. 


Fig.  173. 


The  shape  of  some  of  the '^Vhitworth  projectiles  approach  more 
nearly  to  this  form  than  those  of  any  elongated  projectiles 
hitherto  used.  (Art.  .) 


6 4^ 

d- -b 

Fig.  173. 


782.  Studded  Peo.tectiles. — These  are  fitted 
for  rifling  of- the  second  class.  (Art.  760.)  The 
studs  arc  usually  of  bronze,  the  proportions  of  the 
alloy  being  from  seven  to  ten  parts  of  copper  to 
one  of  tin,  which  is  sufficiently  soft  to  enable  the 
stud  to  be  attached  to  the  projectile  by  pressing 
it  into  under-cut  holes  in  the  latter,  causing  the 
end,  which  is  cupped  or  hollowed  out,  to  expand 
and  rivet  itself  firmly  in ; it  is  swedged  cold  into 
the  holes.  (Fig-  173.) 


PROJECTILES. 


271 


Tn  studding  a projectile,  two  rings  of  eircular  holes  are  usu- 
ally cast  in  tlie  walls,  the  number  of  holes  in  each  ring  corre- 
sponding to  the  number  of  grooves  in  the  gun.  The  weaken- 
ing of  the  walls  by  so  many  holes, 
arid  the  concentration  of  the  effort 
of  rotation  at  these  points,  seriously 
affects  the  endurance  of  the  projec- 
tile. 

7S3.  The  system  of  studding  to 
accommodate  the  increasing  spiral, 
c;m  be  readily  understood  by  Fig. 

ITd,  and  the  following  explanation. 

FE',  DD'  represent  the  groove  at 
seat  of  projectile ; AA',  BB'  repre- 
sent the  groove  at  the  muzzle. 

O and  O'  are  the  studs. 

The  object  sought  is  to  combine 
a double  bearing  with  an  accelerated 
spiral.  The  chtliculty  lies  in  the 
fact,  that  since  the  angle  at  wdiich 
the  grooves  are  inclined  is  continu- 
ally increasing,  the  gun  would  he 
trying  to  turn  the  fore  part  of  a 
rigid  projectile  faster  than  the 
hinder  part,  which  would  be  impos- 
sible. 

To  overcome  this  difficulty,  the 
rear  stud  is  made  larger  than  the 
front  one.  Thus,  at  starting,  the 
three  rear  studs  do  all  the  work  of 
turning  the  projectile,  since  EE'  is 
the  driving-edge  of  the  groove 
when  it  commences  to  move.  This 
work  is  inconsiderable,  as  the  angle 
of  the  twist  at  first  is  zero.  But  as 
the  projectile  travels  along  the  bore, 
the  friction  will  wear  down  the  rear 
studs,  and  the  assistance  of  those  in 
front  will  he  gradually  called  into 
play.^ 

The  rear  studs  are  made  large 
enough  to  fill  the  grooves ; the  size 
and  position  of  the  front  stud  is  thus 
determined.  Draw  AA'  tangent  to 
A'AII 


' a 


the 


makino-  an  an2;le 

O O 


AA'  tangent 

final  angle  of 


larger 

rifling. 


stud  at  C,  and 
From  O,  the 


/ 


272 


NAVAL  ORDNANCE  AND  GUNNERY. 


centre  of  the  rear  stud  draw  00^,  maliing  O'OH  = ^ A'AII. 
It  Avill  readily  he  seen  that  a circle  described  with  any  point  O' 
as  a centre  along  the  line  00',  and  the  perpendicular  O'P  let  fall 
upon  BB'  as  a radius,  will  touch  DD',  and  that  the  projectile 
will  freely  enter  the  gun,  and  that  the  bearing-edges  of  the  stud 
will  all  press  equally  on  the  driving-edges  of  the  grooves  as  the 
projectile  approaches  the  muzzle. 

The  front  stud  touches  the  dilving-edge  on  entering  the  bore, 
and  the  loading-edge  when  well  home ; and  the  reverse  action 
occurring  in  bring,  the  share  it  takes  in  the  work  of  rotation  is 
very  small,  for  until  the  driving-edge  meets  it,  the  whole  pres- 
saire  is  on  the  rear  studs.  Its  chief  use  appears  to  be  to  steady 
the  projectile. 

781.  These  projectiles  must  he  handled  and  stored  with 
great  cai'e  to  prevent  the  studs  being  bruised  and  injured  so  as 
to  jam  in  the  bore,  or  fail  to  grip  on  the  grooves  in  bring. 

They  are  liable  to  break  up  in  the  bore  if  bred  a second 
time,  and  the  studs  are  liable  to  sheer  and  thus  prevent  the  cen- 
tring of  the  projectile. 

785.  Exi’anding  Beojectiles. — These  are  used  with  ribing 
of  the  Third  Class.  (Art.  761.) 

All  the  projectiles  used  in  the  naw)"  for  ribed  ordnance  are 
of  the  Expanding  Class ; being  forced  to  take  the  grooves  by 
the  action  of  the  charge  of  powder,  and  require  no  other  pre- 
caution in  loading  than  spherical  shell.  It  is  essential,  how- 
ever, that  the  base-ring  of  every  ribe  projectile,  especially 
the  Parrott,  shall  be  greased  before  entering  it  into  the 
gun,  to  prevent  the  formation  of  a hard  deposit  in  the 
grooves. 

Parrott  Projectile.— V&i'voith  projectile  is  composed  of  a 
cast-iron  body  and  brass  ring  cast  into  a rabbet  formed  aroimd 
its  base. 

The  ring  is  from  1 in.  to  11  in.  in  width,  and  about  1 in. 
in  maximum  depth.  The  gas  presses  against  the  bottom  of  the 
ring  and  underneath  it,  so  as  to  expand  it  into  the  grooves  of 
the  gun.  (Eig.  175.) 

To  prevent  the  ring  from  turning  in  the  rabbet,  the  latter 
is  recessed  at  several  points  of  its  circumference,  like  the  teeth 
of  gearing. 

The  diameter  of  the  rabbet  is  greatest  at  the  extreme  rear 
of  the  shot,  so  that  the  brass  ring  cannot  by  off  without  break- 
ing. Tdie  entire  projectile  is  slightly  smaller  than  the  bore,  so 
as  to  be  easily  rammed  home. 

Very  few  of  the  rings  have  been  broken  in  practice ; they 
should  be  separated  from  the  iron  base  of  the  projcctbe  at 


PEOJECTILES. 


27a 


three  or  four  parts  of  the  circumferenee,  in  case  any  fail  to  ex- 
pand and  take  tlie  grooves. 

This  should  be  done  very  lightly  with  a cold-chisel,  so  as 
not  to  interfere  with  loading.  It  is  only  necessary  to  sever  the 


contact  of  the  two  metals.  The  use  of  a little  grease  or 


lubricating  material  around  the  rinc 
firing,  is  advantageous. 


other 

of  the  projectile,  before 


Fig  176. 


186.  Dalilgren  Projectile. — 

Dahlgren’s  rifie  projectile  con- 
sists of  a cast-iron  cylindro-coui- 
cal  projectile  with  a leaden  cup 
attached  to  its  base ; offsets  from 
the  cup  entering  into  recesses  in 
the  iron  securely  attach  the  cup 
to  the  projectile.  (Fig.  176.) 

There  are  projections  cast  on  the 
cylindrical  portion  which  are  but 
slightly  raised  from  the  surface  of 
the  shot ; and  in  the  groove 
around  the  cup  is  placed  a mixture 
of  tallow  and  lamp-black,  which 
lubricates  the  bore  after  each  discharge. 

787.  The  ShenJde  Projectile.  — s>  projectile  is  com- 
posed of  a cast-iron  body,  having  its  greatest  diameter  a little/ 
more  than  -J-  of  its  length  from  the  forward  end,  from  which 
point,  to  the  rear  end,  it  presents  the  form  of  a truncated  cone, 
with  straight  projections  cast  upon  it.  (Fig.  178.) 

Around  the  rear  portion  is  placed  a ring  of  jgapier^iaclie 
(Fig.  179),  the  interior  of  which  is  made  conical  and  grooved, 
to  fit  the  projections  on  the  casting ; so  that  there  shall  be  no 
lateral  slipping  ; the  exterior  is  cylindrical  and  slightly  smaller 
than  the  bore,  so  as  to  run  home  easily.  The  powder-gas 
drives  jga'pier-mache  ring  forward  upon  the  case,  whence  it. 

18 


274 


NAVAL  ORDNANCE  AND  GIINNERT. 


is  jammed  into  the  grooves  of  the  gun,  and  made  so  compact 
as  to  rotate  the  projectiles  without  strippiirg.  On  issuing  from 


Fig.  177. 


the  bore  the  ring  is  blown  to  pieces,  leaving  the  projectile  unen- 
cumbered in  its  flight. 

A great  difficulty  has  been  found  in  practice  in  always  get- 
ting a proper  quality  of  material  for  the  sabot  ring. 

These  projectiles  have  gone  out  of  use,  as  the  papier-mache 
case  was  found  to  swell  and  e.xpand  upon  being  exposed  to 
dampness  and  moisture. 

788.  IIotchHss  Projeciile. — The  Hotchkiss  projectile  is 
■composed  of  three  parts.  It  consists  of  a cast-iron  body  with  a 
cylindrical  base  of  diminished  diameter,  over  which  a cast-ii-on 
cap  is  fitted.  These  parts  are  slightly  less  in  diameter  than  the 
'bore  of  the  gun.  The  groove  between  the  body  and  the  cap 
contains  an  expanding  ring  of  lead ; offsets  from  the  lead  enter- 
ing into  recesses  in  both  the  iron  parts,  and  holding  all  secure. 
(Fig.  181.) 

The  first  power  of  the  powder,  befoi’e  the  inertia  of  the 
whole  projectile  is  overcome,  is  devoted  to  driving  the  cap 
farther  upon  the  body,  thus  squeezing  out  the  intermediate  lead 
into  the  grooves  of  the  gun,  and  at  the  same  time  holding  the 
lead,  as  in  a vice,  so  that  it  cannot  revolve  on  the  projectile. 
AYhen  discharged,  the  base-piece  is  dri\-en  forward  upon  the 
Tront  piece  to  an  extent  which  is  definitely  limited  by  its  con- 
tact with  the  extreme  rear,  and  by  this  movement  expands  the 
soft-metal  ring  to  an  amount  jnst  sufficient  to  fill  the  gun  and 
take  the  grooves. 


PROJECTILES. 


275 


789.  Lead-coated  Peojectiles. — These  are  used  with  rifling 
of  the  fourth  class.  (Art.  767.) 

To  attach  the  lead-coat  the  surface  of  the  iron  is  well  cleaned, 


and  covered  with  a zinc  solder,  when  the  lead  is  cast  directly  on 
that.  The  zinc  amalgamates  sufficiently  with  the  iron  and  lead 
to  give  a very  complete  attachment.  In  order  to  get  a clean 
metallic  surface  to  wdiich  the  zinc  may  adhere,  the  projectile  is 
dipped  into  a sal-ammoniac  solution  ; the  next  operation  con- 
sists in  dipping  the  projectile  into  molten  zinc. 

The  lead-coat  occasionally  becomes  detached  in  spots,  where 
the  lead  has  risen  up  into  blisters  from  the  for- 
mation of  gas  underneath  it,  occasioned  by  vol- 
taic action  between  the  different  metals.  Such 
blisters  are  generally  very  small,  and  may  be 
pricked  and  then  hammered  down,  without 
affecting  the  fitness  of  the  projectile  for  service. 

If  left  to  develop  th.emselves  they  have  been 
known  to  attain  a large  size.  In  the  German 
service,  the  lead-coat  is  covered  with  a mixture 
of  beeswax  and  benzine  applied  warm,  and 
rubbed  smooth  with  flannel  rags.  This  does 
away  with  any  necessity  for  lubricating  the 
bor^  (Fig.  182.)  ^ Fig.  182. 

790.  The  lead-coating  is  preserved  from  in- 
jury  by  two  grommets  which  are  nearly  cut  in  two  to  facilitate 


V. 


276  NAVAL  ORDNANCE  AND  GUNNERY. 

removal,  and  the  projectiles  are  stored  in  racks  fitted  in  the 
shell-room. 

Sometimes  the  body  of  the  projectile  is  not  strictly  cylindri- 
cal, but  rather  smaller  at  the  base,  the  lead-coating  bringing 
the  finished  body  into  a cylinder.  This  form  is  considered 
good  for  j)enetration,  but  any  lead-coating  must  considerably 
retard  the  projectile  in  endeavoring  to  force  its  way  tlmougii 
armor. 

This  lead-covering  causes  a great  waste  of  power,  as  it  is  the 
iron  part  alone,  of  the  shell,  that  can  do  work  against  the  iron 
plates,  and  consequently  a considerable  force  is  expended  in 
projecting  a part  of  the  projectile  which  is  useless  for  the  work 
which  has  to  be  performed. 

791.  SOLID  PROJECTILES. — Solid  projectiles  when 
used  in  heavy  guns  are  known  as  solid-shot,  round-shot,  or  shot. 
They  are  employed  to  destroy,  fracture,  or  penetrate  an  object 
by  the  mere  force  of  impact,  and  are  used  when  great  range,  ac- 
curacy, and  penetration  are  required.  Solid  shot  are  classified 
according  to  their  weight. 

792.  HOLLOW  PROJECTILES. — Under  the  head  of 
Hollow  Projectiles  are  included  shells  for  guns,  howitzers,  and 
mortars.  These  are  usually  made  of  cast-iron,  and  are  classified 
according  to  the  diameter  of  the  bore  of  the  piece. 

793.  Shell. — A shell  is  a hollow  pi’ojectile  filled  with  gun- 
powder, which  is  ignited  by  a fuze  at  the  required  moment,  the 
bursting  of  the  shell  causing  destruction  by  its  explosive  force 
and  by  the  fragments,  and,  if  the  object  be  combustible,  by  set- 
ting it  on  fire. 

The  thickness  of  metal  must  be  such  that  the  shell  may 
contain  as  large  a bursting-charge  as  possible,  but  that  it  be 
strong  enough  to  withstand  the  shock  of  the  discharge  within 
the  bore  of  the  gun. 

The  thickness  of  metal  in  a spherical  shell  is  about  one- 
sixth  of  the  diameter,  and  the  weight  of  the  shell  is  about 
three-fourths  that  of  the  solid-shot  of  the  same  calibre. 

Crane’s  IX-in.  Shell  consists  of  a shell  within  a shell.  The 
advantage  claimed  is  that  upon  bursting  it  separates  into  double 
the  number  of  pieces. 

It  is  made  by  first  casting  an  Ylll-in.  shell  with  a IX-in. 
core ; this  casting  (when  sumciently  set,  and  before  cold)  is 
used  as  the  core  for  a IX-in.  shell. 

Pevet’s  Shell  is  made  similar  to  the  Crane’s,  excepting 
that  there  is  a space  of  about  seven-tenths  (7-lOths)  of  an  inch 
between  the  two  shells,  which  is  filled  with  small-sized  iron 
balls. 


PKOJECTILES. 


277 


The  shell  of  a I’ifle-gnn,  being  elongated,  is,  hy  giving  it  a 
greater  length  than  the  shot,  brought  up  to  the  same  weight  as 
the  latter. 

794.  Moktae-shells  are  fired  from  Mortars  at  high  angles, 
being  intended  to  fall  upon  and  set  fire  to  buildings,  vessels, 
or  other  combustible  constructions  ; to  destroy  earth-works,  or 
by  their  great  penetration  before  bursting  to  explode  maga- 
zines protected  from  other  projectiles. 

They  are  fitted  with  two  lugs  placed  one  on  each  side 
of  the  fuze-hole,  which  serve  for  attaching  a pair  of  sliell- 
hoolcs. 

The  fuze-holes  of  mortar-shells  are  larger  in  diameter  than 
those  of  other  common  shells,  and  they  are  not  countersunk  or 
bouched  with  composition. 

795.  CASE-SHOT. — Case-shot  are  a collection  of  small 
projectiles  enclosed  in  a case  or  envelope. 

The  envelope  is  mtended  to  be  broken  in  the  piece  by  the 
shock  of  the  discharge,  or  at  any  point  of  its  flight  by  a charge 
of  powder  enclosed  within  it ; in  either  case  the  contained  pro- 
jectiles continue  to  move  on  after  the  rupture,  but  scatter  out 
into  the  form  of  a cone ; so  as  to  cover  a large  surface  and  at- 
tain a great  number  of  objects. 

The  three  principal  kinds  of  case-shot  in  use  are  grajje,  caiv- 
ister^  and  shrapnel. 

They  are  adapted  to  all  guns,  and  receive  their  names  froin 
the  pieces  in  which  they  are  used. 

796.  Shrapnel. — Shrapnel  are  thin-sided  shell,  in  which  are 
placed,  besides  the  bursting-charge  of  powder,  a number  of  small 
balls  embedded  in  sulphur.  The}"  are  cast  in  the  same  maimer 
as  ordinary  shell,  excepting  that  their  sides  are  made  thinner  to 
allow  for  a greater  number  of  balls.  The  charge  of  powder  is 
quite  small,  being  only  sufficient  to  rupture  the  case  and  liberate 
the  balls. 

The  thickness  of  the  metal  should  be  such  that  it  will  resist 
the  explosion  of  the  charge  within  the  bore  of  the  gun,  but  open 
readily  with  a small  bursting-charge.  The  bursting-charge  should 
be  merely  sufficient  to  open  the  shell  without  affecting  the  flight 
of  the  bullets. 

A spherical  shell  of  this  class  has  a less  thickness  of  metal 
than  a common  shell,  viz.,  about  one-tenth  of  its  diameter,  and 
its  weight  when  empty  is  about  half  that  of  a solid  shot  of  shni- 
lar  diameter.  (Fig.  183.) 

797.  Filling. — -To  fill  a shrapnel  a funnel  is  screwed  into 
the  fuze-hole,  and  the  ease  filled  with  the  recpiisite  number  of 
balls.  A round,  hollow  steel  mandrel,  made  slightly  tapering 


278 


NAVAL  ORDNANCE  AND  GUNNERY. 


towards  the  lower  end,  which  is  ronnded  oS,  and  harins:  a score 
cut  on  either  side  throughout  its  length  to  admit  of  a free  pas- 
sage for  the  melted  sulphur  to  the  interior  of  the  shrapnel,  is 
driven  and  worked  through  the  fuze-hole  to  the  bottom  of  the 
case.  The  projectile  is  then  thoi’oughly  warmed,  generally  in 
warm  water,  to  prevent  the  cold  metal  from  solidifying  the  sul- 
phur before  it  has  filled  all  the  interstices. 

It  is  then  filled  with  melted  sulphur,  and  as  soon  as  the  sul- 
phur is  set  the  mandrel  is  withdrawn  : this  is  accomplished  by 
first  heating  it  from  the  interior  by  the  insertion  of  a hot  rod. 
wdien  it  is  readily  removed.  The  funnel  is  also  removed,  and 
the  inagazine  formed  by  the  mandrel  is  cleaned  and  the  fuze- 
hole  carefully  tapped  out.  ' 

In  this  magazine  is  deposited  the  charge  of  powder,  where 
it  is  protected  against  all  injury  from  the  movement  of  the  balls. 
By  this  arrangement  the  cpiantity  of  powder  required  to  open 
the  shrapnel  is  very  small,  and  the  bullets  are  prevented  from 
striking  by  tlieir  inertia  against  the  sides  of  the  case  and  crack- 
ing it  when  the  piece  is  fired. 

Lead  being  much  more  dense  than  iron,  the  shrapnel  is, 
when  loaded,  nearly  as  heavy  as  a solid  shot  of  the  same  calibre 


Fig.  183. — Section  of  12-pdr.  shrapnel,  with  Bormann  fuze  and  filling  of 

sulphur. 


for  the  lighter  guns.  A shell  of  this  class  is,  in  fact,  simply  a 
canister-shot  adajrted  to  long  range.  The  rupture  may  be  made 
to  take  place  at  any  point  of  its  flight,  and  in  this  respect  it  is 
superior  to  canister  and  grape  shot,  wluch  begin  to  separate  the 
moment  they  leave  the  piece. 


PEOJECTILES.  279 

Table  of  contents  and  weights  of  spherical  shrapnel  for  navy 

guns. 


Calibre. 

Weight  of 
empty  shell. 

Contents. 

^ t) 
-2* 
^ o 

No.  o£ 
balls. 

Size  o£ 
balls. 

I>bs.  of 
sulphur. 

Bursting- 

charge. 

XV-inch  .... 

178  lbs. 

1,000  iron. 

1 inch. 

30. 

10  oz. 

358  lbs. 

Xl-inch 

76  “ 

625  iron. 

0.85  “ 

10. 

6 

141  “ 

X-incli 

57  “ 

435  iron. 

0.85  “ 

8.5 

4 “ 

101  “ 

IX-inch 

.38  “ 

350  iron. 

0.85  “ 

7. 

3 

7o  ‘‘ 

Vlll-inch... . 

29  “ 

220  iron. 

0.85  “ 

G . 

2.5  “ 

52  “ 

32-pdr 

15  “ 

235  lead. 

0.65  “ 

2.25 

1.25  “ 

32  “ 

24-pdr  

11  “ 

175  lead. 

0.65  “ 

1.5 

450  grs. 

24  “ 

12-pdr 

6.5  “ 

80  lead. 

0.65  “ 

0.75 

350  grs. 

12  “ 

798.  Rifle-siieap^'el. — In  the  Boxer  shrapnel  for  tlie  riiiec]- 
ordnance  of  the  English  service  tlie  es- 
sential features  of  a shrapnel-shell  are 
einhocliecl. 

This  shell  (Fig.  181)  has  a cylindri- 
cal iron  body,  with  a chamber  at  the 
hot!-om,  and  four  longitudinal  grooves 
inside  to  facilitate  breaking  up;  it  is 
cast  without  a head.  A tin  case  for 
the  bursting-charge  tits  into  the  chamber, 
on  the  shoulder  of  which  rests  a wrought- 
iron  disk.  The  shell  is  lined  with  paper, 
and  filled  with  halls  embedded  in  rosin. 

A wrought-irou  tube  passes  down  the 
middle  of  the  shell  and  through  a hole 
in  the  centre  of  the  iron  disk,  to  lead 
the  flame  from  the  fuze  to  the  burstim;- 
charge.  K disk  is  placed  over  the  top 
of  the  bullets. 

The  wooden  head  is  ogival  in  form, 
and  made  of  elm  covered  with  thin 
wrought-iron,  which  is  riveted  to  the 
shell.  This  head  contains  a socket  and 
bouchino'  for  the  fuze. 


799.  GnAPE-snoT. — A grape-shot  is  Fig.  184. 

composed  of  a number  of  small  shot  ar- 
ranged around  a spindle  on  an  iron  disk.  Formeily  the  shot  were 


280  ' 


NAVAL  OEDNANCE  AND  GUNNERY. 


1 


la 


m 


(7 


Fig.  185. 


enclosed  in  a canvas-bag,  which  was  drawn  together  between  the 
balls,  or  “quilted  ” by  a strong  line;  but  the  present  method  is 
more  simple  and  durable.  It  consists  of  nine  shot  of  a size  appro- 
pi'iate  to  the  calibre  used,  which  are  held  together  by  two  rings  and 
a plate  at  each  end  of  the  stand  connected  by  a rod.  (Fig.  185.) 

The  diameter  of  balls  for  grape-shot  varies 
wdth  the  calibre,  being  in  all  cases  larger  than 
those  used  for  canister. 

Grape-shot  are  now  nearly  obsolete,  it  being 
considered  that  canister-shot  are  sufficient  for 
short  ranges ; and  the  canister-shot  possesses  the 
advantage  of  striking  a great  many  more  points 
at  one  discharge  than  grape.  There  is  an  advan- 
tage, too,  in  not  having  so  many  different  kinds 
of  ammunition. 

It  is  the  intention  to  abolish  grape  as  soon  as 
the  stock  on  hand  is  exhausted. 

800.  Canistee-siiot. — A canister-shot  is  a 
metallic  cylinder  about  one  calibre  in  length,  filled  with  balls 
and  closed  at  both  ends  with  woodeir  or  metal  disks.  They  are 
supplied  for  all  guns. 

For  8-inch  canister,  and  all  those  of  less  calibre,  the  envelope 
is  made  of  tin,  while  canister  for  the  larger  calibres  have  an  en- 
velope of  iron. 

The  bottom  of  XY-ineh  canister  is  made  of  two  thicknesses 
of  1-inch  hard  wood,  crossing  each  other,  and  put  together  with 
wrought-iron  nails  clinched.  A spindle,  with  a wrought-iron 
handle  passing  through  the  centre  of  the  canister,  is  riveted  on 
the  bottom  through  a square  plate.  All  other 
canister  have  bottom-heads  of  one  thickness  of 
hard  wood.  Top-heads  are  all  made  of  white- 
pine. 

The  case  is  notched,  turned  over  the  heads, 
and  tacked  down. 

The  balls  for  all  canister  are  1.3  inch  dia- 
meter, and  the  number  used  varies  with  the 
calibre.  To  give  more  solidity  to  the  mass, 
and  prevent  the  balls  from  crowding  upon 
each  Other  when  the  piece  is  fired,  the  inter- 
stices are  closely  packed  with  sawdust. 

801.  Eifle-canister. — These  are  very  sim- 
ilar in  general  appearance  to  those  used  in 
smooth-bore  cannon.  (Fig.  186.) 

The  case  is  of  sheet-iron,  or  tin,  with  frmged  ends  which  are 
turned  over  and  soldered  or  riveted  to  iron  or  zinc  disks. 


PEOJECTILES. 


281 


The  balls  are  of  iron  or  zinc  packed  in  rosin  or  coal-dust, 
sometimes  in  disks  of  wood.  (Fig.  187.) 


Eig.  187. 


They  are  fitted  with  solder  studs  or  rings  of  lead  on  the  out- 
side to  take  the  rifling  (Fig.  187),  or  with  an  expanding  cup 
(Fig.  186). 

dlATXD-GEENADEs  consist  of  Small  cylindrical  shaped  shell, 
with  conical  ends,  fitted  with  a plunger  at  the  striking-end,  and 
a directing-feather  at  the  other.  The  plunger  fits  loosely  into 
the  cavity  in  the  forward  part  of  the  shell,  and  is  made  to  pro- 
ject two  or  three  inches  beyond  its  face,  being  retained  in  place 
by  a slight  spring ; it  has  attached  to  its  outer  end  a circular 
piece  of  sheet-iron  several  inches  in  diameter.  At  the  bottom 
of  the  cavity  in  which  the  plunger  is  placed  a nipple  is  fixed, 
communicating  with  the  bursting-charge,  on  which  is  placed  an 
ordinary  percussion-cap,  whidi  is  exploded  when  the  plunger  is 
driven  in  violently,  thereby  igniting  the  charge. 

There  are  three  sizes  of  grenades,  one  (1),  three  (3),  and  five 
(5)  pounds,  and  are  intended  to  be  thrown  by  hand,  and  may  be 
very  effectively  used  in  repelling  attacks  by  boats  or  by  persons 
well  sheltered  against  others  completely  exposed. 

802.  FABE1CATIOJ7  OF  PROJECTILES.— They  are 
usually  made  of  gray  or  mottled  cast-iron  of  good  quality. 
Shells  should  be  made  of  the  best  cpiality  of  iron,  and  with  par- 
ticular care,  in  order  that  they  may  not  break  in  the  gun. 

803.  Patteen. — The  pattern  of  a spherical  projectile  is  com- 
posed of  two  hollow  cast-iron  hemispheres,  which  unite  in  such 
a manner  as  to  form  a pei’fect  sphere ; on  the  interior  of  each 
lieraisphere  is  fastened  a handle  to  enable  the  operator  to  ch-aw 
it  from  the  sand  when  the  half-mold  is  completed.  The  fla-sJcs 
which  contain  the  mold  are  made  of  iron,  in  two  ecpial  parts, 
united  by  means  of  hooks  at  their  larger  bases.  The  other  ends 
are  fitted  with  movable  covers.  (Fig.  188.) 


282 


NAVAL  OEDNANCE  AND  GIJXXERT. 


804.  Molding. — This  operation  is  performed  by  placing  the 
flat  side  of  one  of  the  hemispheres  on  the  molding-board  and 


Fig.  188. 

corering  it  -rdth  a flask.  Sand  is  then  poured  into  the  flask, 
filling  np  the  entire  space  between  it  and  the  hemisphere,  and 
well  rammed.  Tlie  cover  is  then  attached,  and  the  flask  turned 
over,  the  hemisphere  is  withdrawn,  and  the  entire  surface  of 
the  sand  painted  with  coke-wash  and  dried. 

The  remaining  half  of  the  mold  is  formed  in  the  same  way, 
except  that  a channel  for  the  introduction  of  the  melted  iron  is 
made  by  inserting  a round  stick  in  tlie  sand  before  it  is  rammed 
and  withdrawing  it  afterwards.  A,  dig.  ISS. 

805.  Hollow,  Pbojectiles. — TTms  far  the  operations  of 
molding  and  casting  solid  and  hollow  projectiles  are  the  same. 
The  cavity  of  a hollow  projectile  is  formed  by  inserting  a core 
of  sand.  This  is  a sphere  of  the  proper  size,  made  by  compres- 
sing the  molding-composition  on  a half-inch  hollow  non  spindle 
by  means  of  two  hemispherical  cups.  (Tig. 

The  requisite  compression  being  given  by  screws.  The  core 
is  by  means  of  a gauge  placed  exactly  in  the  centre  of  the  mold 
and  supported  in  that  position  by  the  stem  Avhich  forms  the 


PEOJECTILES. 


2S3 


fuze-hole.  The  stem  is  perforated  witli  small  holes  to  allow  of 
the  escape  of  steam  and  gas  generated  by  the  heat  of  the  melted 


metal,  that  part  of  it  which  comes  in  contact  with  the  melted 
iron,  and  forms  the  fuze-hole  is  coated  with  sand. 

In  pouring  the  melted  iron  into  the  mold  with  the  ladle  cai-e 
should  be  taken  to  prevent  scoria  and  dirt  from  entering,  with 
it,  and  for  this  purpose  the  surface  should  be  skimmed  with  a 
wooden  stick. 

After  the  iron  has  become  sufficiently  hardened  the  flasks 
are  opened  and  the  sand  knocked  from  the  casting.  Then  the 
core  is  broken  up  and  removed,  and  the  interior  surface  cleaned 
by  a scraper. 

The  greatest  care  is  to  be  taken  to  remove  every  particle  of 
sand  or  fragment  of  iron  from  the  interior. 

The  sinking-head  or  projecting  portion  at  the  gate,  and 
around  the  base  where  the  two  halves  join,  are  taken  olf  with  a 
file  or  chisel  if  necessary. 

A number  of  the  balls  are  now  placed  in  a large  revolving 
iron  cylinder,  which  by  friction  polishes  and  makes  the  surface 
more  uniform. 

806.  Bouching. — The  fuze-holes  of  all  shell  are  bouched 
with  gun-metal  to  receive  the  Is  avy -fuze-stock.  In  fitting  the 
shell  to  receive  the  borrohing,  the  bore  should  be  tapped  with  a 
full  thread,  and  the  proper  shoulder  left  at  the  bottom  to  pre- 
vent the  bouching  from  being  driven  in  by  the  shock  of  firing 
and  causing  premature  explosion. 

The  object  of  the  bouching  is  to  prevent  ruct,  and  to  have 


284 


NAVAL  OEDNANCE  AND  GUNNERY. 


the  same  kind  of  metal  in  contact  ,with  the  fnze-stock,  so  that 
there  will  he  less  danger  in  extracting  or  exchanging  a fuze. 

The  fuze-holes  of  heavy  riile-shell  are  necessarily  cast 
larger  than  the  diameter  of  the  regular  fuze-stock,  wliich  can, 
however,  be  used  wdth  the  aid  of  an  adapting-ring  of  gun- 
metal,  which  is  screwed  in  to  reduce  the  diameter  of  the  hole 
to  the  proper  dimensions. 

The  fifteen -inch  spherical  shell  are  cast  with  three  fuze- 
holes  ecpially  distant  from  each  other,  and  situated  in  the  an- 
gles of  a triangle  4 inches  apart. 

807.  CHILLED  PROJECTILES. — Chilled-iron  projec- 
tiles have  been  profitably  employed  to  pierce  armor-plates,  on 
account  of  their  intense  hardness. 

808.  Pallisee  Peojectiles. — The  English  projectiles  rec- 
ommended by  Major  Palliser  may  he  described  as  an  example 
of  chilled  projectile. 

The  form  of  these  are  cylindro-conoidal,  the  head  being 
ogival,  struck  with  a radius  of  diameters.  The  total  length 
varies  between  2 and  2|-  calibres.  The  bottom  is  flat,  and  in 

the  centre  of  the  bottom  is  a filling- 
hole  for  shells,  closed  with  a com- 
position screw-plug.  (Fig.  190.) 

All  Palliser  shells  are  lacquered 
internally  to  give  them  a smooth, 
clean  lining,  Avhich  prevents  the 
iron  from  either  oxydizing  at  the 
expense  of  the  powder,  or  firing 
it  from  friction  by  rapid  rotation 
during  flight.  As  the  lacquer  does 
not  always  hold  well  to  the  metal, 
serge-bags  are  introduced  to  con- 
tain the  bursting-charge  as  an 
additional  prevention  against  pre- 
mature ex|)losion.  These  bags  are 
made  bottle-shaped,  and  are  intro- 
duced through  the  filling-hole. 

Palliser  shot  are  cored.  The 
hollow  up  the  centre  enables  them 
to  cool  more  uniformly,  and  ren- 
ders them  less  liable  to  split.  It 
also  slightly  hnproves  its  proportions  and  its  regularity  of  flight. 
The  bottom  is  closed  with  a plug. 

809.  How  made. — These  projectiles  are  made  of  carefidly 
selected  iron,  which,  if  run  in  sand-molds,  woidd  solidify  as  mot- 
tled, iron. 


Fig.  190. 


PEOJECTILES. 


285 


The  projectiles  are  east  point  down,  for  the  sake  of  density 
and  soundness  in  the  head.  The  mold  is  formed  of  a metal- 
chill  at  the  bottom  extending  up  past  the  junction  of  head  and 
body  ; the  remainder  of  the  mold  is  formed  of  sand,  as  also  is 
the  case  for  the  formation  of  the  interior.  The  chilling  action 
therefore  extends  a little  past  the  head  of  the  projectile,  which 
thus  has  a mottled  body  and  a white  head. 

The  Griison  projectiles  are  east  with  a dead-head  on  the 
base,  which  is  afterwards  cut  off,  the  object  being  to  obtain  a 
solid  bottom  to  stand  well  under  the  shock  of  the  discharge. 
The  chilling  is  effected  by  the  metal  molds,  in  virtue  of  their 
great  conducting-power,  their  thickness  greatly  affecting  the  ex- 
tent of  their  action.  The  head  thus  chilled  white,  possesses 
generally  the  quality  of  Avhite-irou,  intense  hardness,  crushing- 
strength,  considerable  brittleness,  and  increased  density. 

The  tip  or  point  of  a chilled  projectile,  is  occasionally 
broken  off  by  the  impact  of  a shell  or  shot  rolled  or  struck  ob- 
liquely against  it ; for  the  point  which  may  penetrate  directly 
through  many  inches  of  armor  without  injury,  may  be  frac- 
tured by  a very  slight  transverse  blow. 

810.  Steel  Peojectiles  have  proved  more  efficient  than 
those  of  any  other  metal,  but  their  expense  has  heretofore  been 
too  great  to  warrant  their  general  use.  For  rifle  projectiles 
they  are  made  from  solid  ingots  of  steel  turned  to  form,  and 
bored  out  for  shells.  They  are  hardened  by  heating  and  cool- 
ing quickly,  the  head  being  to  a certain  extent  chilled.  The 
manufacture  is  expensive  and  tedious,  and  the  tempering  is  a 
matter  of  difficulty,  the  shells  being  liable  to  crack.  In  or- 
der to  overcome  this  difficulty  hollow  shot  have  been  devised, 
the  hole  through  the  centre  allowing  the  sudden  shrinkage  to 
take  place  without  the  injurious  effects  above  alluded  to. 

811.  WhitwortNs  Steel  Shell  we  m.2i6.Q  ivom.  m.got&  oi  steel 
cast  in  the  form  of  hoops,  and  drawn  down  to  the  necessary  size 
under  the  hydraulic  press.  The  ends  are  closed  with  screw 
plugs.  They  are  therefore  less  costly  than  might  be  supposed. 

812.  ITSISPECTIOIT. — Object  of  Ikspection. — The  prin- 
cipal points  to  be  observed  in  inspecting  projectiles  are,  to  see 
that  they  are  of  proper  size  in  all  their  parts,  that  they  are 
made  of  suitable  metal,  and  that  they  have  no  defects,  con- 
cealed or  otherwise,  which  will  endanger  their  use  or  impair 
the  accuracy  of  their  fire. 

As  it  would  be  impracticable  tc  make  all  projectiles  of 
exact  dimensions,  certain  variations  are  allowed  in  fabrication, 
which  are  specified  in  the  “ Ordnance  Insti’uetions.” 

813.  Inspection  oe  Solid  Pkojectiles. — The  projectile  is 


286 


NAVAL  ORDNANCE  AND  GENNERT. 


inspected  while  nnlaccjnered,  perfectly  clean,  and  before  be- 
coming rnsty,  so  tliat  the  eye  can  detect  any  flaws  or  imperfec- 
tions in  the  metal. 

Each  projectile  is  placed  npon  a table  and  examined  to  see 
that  its  surface  is  smooth,  and  that  the  metal  is  sound  and  free 
from-  seams,  flaws,  and  blisters.  If  clusters  of  cavities  - or 
small  holes  appear  on  the  surface,  strike 
the  point  of  the  hammer  into  them,  and 
ascertain  their  depth  with  the  searcher. 
If  the  depth  of  the  cavity  exceeds  0.2 
inch,  the  projectile  is  rejected ; it  is 
also  rejected  if  any  attempt  has  been 
made  to  conceal  defects  by  plugging  or 
filling  holes  in  any  mode  whatever. 

The  projectile  must  pass  in  every  di- 
rection through  the  large  gauge  (Fig. 

] 91),  and  not  at  all  through  the  small 
one ; the  calipers  and  scale  will  deter- 
mine exactly  the  difference  of  diameters 
of  the  same  projectile.  The  ring  and 
cylinder  gauges  are  examined  before  each 
inspection,  and  when  found  to  have  en- 
larged 0.01  of  an  inch,  ai’e  laid  aside  and  marked  as  unservice- 
able. 

The  projectiles  are  next  passed  through  the  cylinder-gauge, 
placed  at  an  inclination  of  about  two  incmes  between  the  ends, 
and  supported  in  such  a manner  as  to  be  easily  turned  from  time 
to  time,  to  prevent  its  being  worn  in  furrows.  Projectiles 
which  slide  or  stick  in  the  cylinder  are  rejected. 

The  next  proof  is  to  drop  a few  taken  indiscriminately 
from  the  lot  under  inspection  from  a height  of  twenty  feet  on 
a solid  platform  of  iron,  or  roll  them  down  an  inclined  plane 
of  the  same  height  against  a mass  of  iron,  after  which  they 
are  again  examined  for  defects  of  metal. 

The  average  weight  of  solid  projectiles  is  determined  by ' 
weighing  at  least  three  parcels,  of  from  20  to  50  each,  taken  in- 
discriminately from  the  lot. 

As  many  of  the  lightest  are  weighed  separately  as  the  In- 
specting Officer  deems  necessary,  and  all  found  to  fall  below 
the  least  weight  allowed  by  the  Ordnance  Instructions  are  re- 
jected. 

811.  Inspection  of  Hollow  Pkojectiles. — The  surface  of 
the  shell  and  its  exterior  dimensions,  form,  weight,  and  strength, 
are  examined  and  tested  as  in  the  case  of  solid  projectiles,  and 
subject  to  all  the  conditions  there  specified. 


PROJECTILES. 


287 


The  shell  is  next  struck  with  a hammer  (Fig.  192),  to  judge 
by  the  ring  or  sound 
whether  it  is  free 
from  cracks  ; and  the 
exterior  and  interior 
diameters  of  the 
fuze  - hole  (which 
should  be  accurately 
reamed)  are  verified, 
and  the  soundness 
of  the  metal  about 
the  inside  of  the 
f u z e - h 0 1 e ascer- 
tained. 

To  determine  the 
thickness  of  the  metal, 
three  points,  at  least,  on  the  great  circle  at  right  angles  to  the 
axis  of  the  fuze-hole  are  measured  (Fig.  192.) ; also  one  at  the 
fuze-hole  (Fig.  193),  and  one  at  bottom.  No  shell  is  received 
which  deviates  more  than  one-tenth  of  an  inch  from  the  proper 
thickness  in  any  part. 

The  shell  is  next  placed  in  a tub  of  water,  which  should  be 


Fro.  193. — Gauge  for  thickness  opposite  fuze  hole. 


deep  enough  to  completely  cover  it.  A pair  of  hand-bellows 
and  a wooden  plug  are  inserted  into  the  fuze-hole,  the  plug  to 
fit  the  fuze-hole  and  the  nozzle  air-tight.  Air  is  then  forced 
by  the  bellows  into  the  shell.  If  there  are  any  air-holes  in  it, 
air-bubbles  will  rise  on  the  surface  of  the  water,  and  the  shell 
is  rejected. 

This  occasionally  occurs  from  the  escape  of  air  from  porous 
spots  which  do  not  extend  to  the  interior  of  the  shells.  In  this 
case  the  action  of  the  bellows  produces  no  increase  of  bubbles, 
which  cease  rising  as  soon  as  the  spots  or  cavities  are  filled  with 
water.  Porous  spots  are  also  detected  by  their  absorbing 
water,  and  drying  slowly  when  exposed  to  the  air,  and  likewise 
cause  the  rejection  of  the  shell. 


288 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  Inspecting  OtEcers  stamp  the  shell  at  one  inch  from 
tlie  fuze-hole  with  their  intials,  also  those  of  the  foundry  at 
which  they  are  cast. 

The  Inspector  or  one  of  his  assistants  innst  be  present  when 
shot  or  shell  are  inspected  ; and  the  stamps  and  marks  are  always 
retained^  in  the  possession  of  the  Inspector. 

shells  are  mutilated  by  chipping  a piece  out  of  the 

815.  Inspectiojt  of  Gkape  and  Canistee. — The  dimensions 
are  verified  by  means  of  a large  and  small  gauge. 


Table  of  Gauges  for  Smooth-bore  Projectiles. 

SHOT. 


Dimensions,  ■Weight. 

XV. 

XIII. 

XI. 

X. 

IX. 

8. 

32. 

Mean  Diameter  (in. ) 

14.80 

12.80 

10.80 

9.80 

8 80 

7.85 

6 25 

TVTenrt  Wp.ijvht  Hhs.  ^ 

440. 

276. 

1G6. 

124. 

90. 

65. 

32.5 

SHELL. 


Dimensions,  Weight. 

XV. 

XIII. 

XI. 

X. 

IX. 

8. 

32. 

24. 

12. 

Mean  Diameter  (in.) 

14.80 

12.80 

10.85 

9.85 

8.85 

7.85 

6.25 

5.67 

4.52 

Thiclcne^s  (in.) 

2.85 

2. ST 

2. 

1.80 

1.60 

1.50 

1.25 

.90 

.70 

Diameter  of  fuze-hole 

.65 

.65 

.65 

.65 

■ .65 

.65 

.65 

Mean  weight,  empty  (lbs.) 

3.30. 

208. 

127. 

95. 

68.50 

50. 

25. 

17. 

8.4 

Weight  of  filled  andsaboted  (lbs.) 

1352. 

216.5 

135.5 

101.50 

73.50 

52.75 

26.5 

Rejected 

fuze-holes. 


GEAPE. 


Dimensions,  Weight. 

XV. 

XI. 

X. 

IX. 

8. 

32. 

Weight  of  Stand  (lbs.) 

34.75 

26.10 

20.4 

S.75 

S9.10 

71.70 

52.20 

37.12 

21.80 

15. 

15. 

IS. 

IS. 

12. 

3.65 

3.34 

2.80 

2.50 

2.50 

125.08 

98.02 

74.10 

53.25 

33.60 

PEOJECTILES. 


289 


SHARPNEL. 


Dimensions,  Weight. 


Mean  of 
empty 
case. 


Balls 


Sulphur 
Bursting 
Weight  complete,  saboted  (lbs. ). . . 


} Gauge  (m.) 

Thickness  (in.). 

Weight  (lbs.) 

'v  Number 

( Diameter  (in.).. , 
i Weight  (lbs.)..., 

(lbs.) 

-charge  loz.) 


XV. 

XI. 

X. 

IX. 

8. 

39. 

24. 

14.80 

10.85 

9.85 

8.85 

7.86 

0.25 

5.07 

1.25 

1. 

.87 

.75 

.69 

.60 

.55 

178. 

76. 

67. 

38. 

29. 

15. 

11. 

1000. 

625. 

435. 

350. 

220. 

235.  lead 

175  .lead 

1. 

.85 

.85 

.85 

.85 

.65 

.65 

140. 

51. 

33.5 

27. 

17. 

14. 

10.5 

30. 

10. 

8.5 

7. 

5. 

2.95 

1.5 

10. 

6. 

4. 

3. 

2.5 

1.25 

450 . grs. 

358. 

141. 

101. 

75. 

.52 

32. 

24. 

19. 


4.53 

.45 

6.5 

80.  lead 
.65 
4.T5 
.75 

350.  grs. 


12. 


CANISTER. 


Dimensions,  "Weiglit. 

XV. 

XI. 

X 

IX. 

8. 

32. 

24. 

12. 

.25 

.25 

.25 

9K 

.25 

.15 

6. 

.35 

1.90 

39 

.15 

5. 

.3 

1.90 

39. 

1 

Height,  finished  (in.) 

14. 

1. 

19. 

5-8 

10.5 

6-8 

9.5 

5-8 

> lO  iT. 
! t- 
CO 

7.75 

.50 

Thictoess  ( (in.) 

Head.  T (j^  ) 

1. 

2. 

5-8 

1. 

1. 

1, 

50 

600. 

315. 

290. 

230, 

162. 

100. 

1.30 

1.30 

1.30 

1.30 

1 30 

1 30 

1.30 
12  5 

Balls  y.  

1 Weight  (lbs.) 

150. 

83. 

70. 

45. 

23. 

5 85 

207. 

120. 

98. 

70. 

50. 

30. 

14.55 

7 7.5 

816.  PKESERYATIOlSr  OE  PEOJECTILES.— They  are 
cleaned  from  rust  and  covered  with  a thin  lacquer,  when  they 
are  first  received  and  when  they  are  stored. 

The  following  colors  are  established  when  put  on  board  ship  : 
all  shot,  black  ; shell,  red ; and  sharpnel,  white.  The  length  of 
fuze  is  stencilled  on  the  shell. 

Covers  of  boxes  containing  projectiles  are  painted  the  same 
color  as  their  contents,  and  the  length  of  the  fuze  of  a loaded  pro- 
jectile is  stencilled  in  black  on  the  box.  Empty  shell,  whether 
in  store  or  in  transportation,  are  most  carefully  protected  from 
dampness.  They  have  the  fuze-bo  aching  coated  with  compo- 
19 


290 


NAVAL  ORDNANCE  AND  GUNNERY. 


sition,  and  the  fuze-hole  is  stopped  hy  a plug  of  very  soft  ^vood 
which  is  well  coated  with  a mixture  of  oil  and  tallow,  and 
screwed  in.  The  ends  of  the  plugs  are  not  sawed  off  even  with 
the  shell,  but  left  square  and  project  sufficiently  to  allow  them 
to  he  imscrewed  by  means  of  a wrench  ; and  when  these  plugs 
are  removed  for  the  purpose  of  fitting  the  shells  for  service, 
they  are  not  thrown  away,  but  preserved  for  future  use. 

817.  Stowage. — They  arc  piled  with  the  fuze-holes  down, 
and  free  from  contact ; under  cover,  when  practicable,  but  with 
free  ventilation.  Projectiles  in  boxes  must  be  stowed  in  tiers 
with  thin  battens  of  wood  between  the  tiers,  so  that  there  may 
be  free  circulation  of  air. 

Platforms  of  masonry,  or  of  condemned  projectiles,  are  pre- 
pared to  pile  them  on.  Square  piles  are  to  be  preferred  where 
there  is  room. 

Projectiles,  after  having  been  piled,  are  so  far  examined 
each  yeai',  as  to  ascertain  if  they  require  to  be  cleaned,  re- 
lacquered, and  repiled  to  secure  their  proper  preseiwation. 

For  the  proper  stowage  and  preservation  of  projectiles  on 
board  ship,  shell-rooms  are  provided,  the  same  care  and  atten- 
tion being  given  to  their  construction,  location,  and  means  of 
lighting  and  flooding  as  in  magazines.  The  loaded  shell,  being 
either  in  boxes  or  bags,  are  stowed  in  the  shell-room  in  tiers  or 
ranges,  held  in  place  by  wooden  battens  if  necessary  ; and  when 
there  are  various  kinds,  they  are  to  be  stowed  on  separate  tiers, 
with  pieces  of  plank  between  them,  in  such  manner  that  each 
kind  can  be  readily  obtained.  It  is  seldom  that  the  shell-room 
will  contain  the  full  allowance  boxed ; the  remainder  will  be  put 
on  board  empty. 

Empty  shell  are  to  be  stowed  on  board  ship  by  themselves, 
in  a dry  place,  unsaboted,  in  bulk.  A sabot,  straps,  tacks,  and 
lashing  is  furnished  for  each  empty  shell;  after  target  practice 
the  number  of  loaded  shells  is  to  be  made  complete. 

818.  Lacqueeixg. — Whenever  projectiles  are  to  receive 
lacquer,  care  is  taken  that  the  quantity  applied  does  not  increase 
the  diameter  more  than  is  indispensably  necessary,  and  in  no 
case  above  established  high  gauge.  Old  lacquer  and  rust  are 
removed  b}^  scraping,  as  far  as  can  be  conveniently  done,  before 
a new  coating  is  applied. 

neither  hammering  nor  beating  is  resorted  to  for  this  pur- 
pose. 

After  numerous  experiments  upon  different  lacquers  em- 
ployed for  the  preservation  of  projectiles  from  rust,  the  French 
have  abandoned  all  of  them. 

The  projectiles  are  simply  piled,  under  sheds  when  practica- 


PROJECTILES. 


291 


ble,  or  in  tlie  open  air,  and,  when  pnt  on  hoard  of  ship,  cleaned 
of  rnst  and  ruhhed  over  with  whale-oil : the  same  means  adopted 
every  three  months  of  the  cruise. 

819.  The  Condition  of  Loaded  Shell,  and  especially  of 
their  fuzes,  is  frequently  examined  into,  taking  out  a fuze  occa- 
sionally so  as  to  detect  any  injury  which  may  arise  from  moist- 
ure, and  such  as  may  he  found  damaged  are  replaced  hy  spare 
fuzes. 

Projectiles  returned  from  cruising  ships  are  emptied,  cleaned, 
and  plugged. 

In  emptying  shell  they  are  handled  carefully  and  placed  on 
a bench  with  a hole  in  it  to  receive  and  support  the  inverted 
shell.  A wooden  vessel  placed  below  receives  the  powder. 

The  powder  which  has  been  removed  from  shells  is  only  used 
for  filling  shell,  as  it  always  contains  a small  quantity  of  grit, 
which  renders  it  unfit  for  general  service. 

All  powder  taken  from  shell  is  sifted,  and  all  dust  and  par- 
ticles of  dirt  removed,  as  far  as  possible,  before  putting  it  into 
barrels. 

Should  the  powder  have  become  caked,  so  as  not  to  be  easily 
removed  by  washing  out  the  shell,  a handful  of  small  iron 
shot  put  in  the  shell  facilitates  this  operation. 

820.  Removing  Fuzes. — Whenever  it  is  expedient  or  neces- 
sary to  examine  the  fuzes  and  loading  of  shell  wliich  have  been 
already  prepared,  great  care  is  observed  in  removing  the  fuze, 
and  it  is  never  done  in  the  shell-room. 

The  fuze-stock  may  generally  be  safely  unscrewed  Avith  the 
fuze-wrench,  taking  care,  in  the  first  place,  to  strike  the  side  of 
the  shell  gently  ivith  a wooden  mallet,  to  detach  the  powder  from 
the  fuze,  to  work  very  slowly,  and  not  to  endea\'or  to  overcome 
any  unusual  resistance.  ISTo  attempt  should  be  made  to  open  a 
shell,  for  the  purpose  of  unloading  it  or  destroying  its  charge, 
in  any  other  way  than  by  unscrewing  the  fuze-stock. 

In  doing  this,  if  the  stock  do  not  yield  at  once  to  an  ordi- 
nary effort  with  the  wrench,  then  the  shell  should  be  marked 
and  immediately  set  aside,  to  be  thrown  overboard. 

821.  To  find  the  number  of  halls  in  a pile ^ multiply  the  sum 
of  the  three  parallel  edges  by  one-third  of  the  number  of  balls 
in  a triangular  face. 

In  a square-pile,  one  of  the  parallel  edges  contains  but  one 
ball ; in  a triangular  pile,  two  of  the  edges  have  but  one  ball  in 
each. 

— V ^ 

bemg  ttie  number  in  the  bottom  row. 


292 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  sum  of  the  three  parallel  edges  in  a triangular  pile  is 
£c  + 2 ; in  a square  pile,  2x  -j-  1 ; in  an  ohlong  pile,  3X  + 2a? 
— 2 ; X being  the  length  of  the  top  row,  and  a?  the  width  of 
the  bottom  tier ; or  3m — a?  -)-  1 ; m being  the  length,  a?  the 
width  of  the  bottom  tier. 

If  a pile  consist  of  two  piles  joined  at  a right-angle,  calcu- 
late the  contents  of  one  as  a common  oblong  pile,  and  of  the 
otlier  as  a pile  of  which  the  three  parallel  edges  are  equal. 


Section  II. — Deviations  I 

822.  Geneeal  Consideeations. — The  term  deviation  must 
be  understood  to  mean  not  only  the  deflections,  right  or  left,  of 
the  line  of  fire,  but  also  the  differences  between  the  ranges  of 
similar  projectiles  fired  under  like  condition  from  the  same 
guns. 

Very  great  irregularities  occur  in  the  paths  of  spherical  pro- 
jectiles. If  a number  of  projectiles  be  fired  from  the  same  gun, 
with  equal  chaiges  and  elevations,  and  with  gunpowder  of  the 
same  quality,  the  gun-carriage  resting  upon  a platform,  and  the 
piece  being  pointed  Avith  the  greatest  care  before  each  round, 
very  few  of  the  projectiles  will  range  to  the  same  distance ; 
and,  moreover,  the  greater  part  will  be  found  to  deflect  consid- 
erably, unless  the  range  be  very  short,  to  the  right  or  left  of 
the  line  in  which  the  gun  is  pointed. 

With  elongated  projectiles  the  fire  is  far  more  accurate,  but 
still  the  ranges  and  deflections  are  subject  to  variations  of 
greater  or  less  amount. 

The  causes  of  the  deviations  of  projectiles,  whether  fired 
from  smooth-bore  or  rifle  guns,  and  independent  of  inaccuracy 
in  pointing,  and  variable  position  of  the  gun-carriage,  rcrowind, 
varialjle  projectile  force,  and  rotation  of  the  earth. 

823.  Effect  of  Wind. — Should  the  wind  be  blowing  in 
gusts  and  be  changeable  in  direction,  it  is  difficult  to  allow  for 
it  in  pointing  the  gun ; but  with  a steady  breeze,  in  a pretty 
constant  direction,  a feAV  rounds  will  generally  be  sufficient  to 
shoAv  the  allowance  necessary.  The  velocity  of  the  wind  is 
very  low  compared  with  that  of  the  projectiles,  but  it  remains 
usually  nearly  the  same  throughout  its  flight,  whereas  the  ve- 
locity of  the  projectile  decreases  rapidly ; it  therefore  fre- 
quently happens  that  the  Avind  appears  to  have  greater  effect 
toAvards  the  end  of  the  range,  and  it  may  be  often  noticed  in 


* Owen. 


PROJECTILES. 


293 


practice,  tliat  projectiles  deviate  in  a rapidly  increasing  curved 
line. 

The  wind,  if  strong,  will  greatly  affect  the  ranges  of  projec- 
tiles; decreasing  or  increasing  the  range  according  as  it  may  be 
blowing  with  or  against  the  projectile. 

The  lower  the  velocity  of  a projectile,  the  greater  will  be 
its  deflection  caused  by  the  wind,  as,  for  instance,  upon  mortar- 
shells,  on  which,  having  low  velocities  and  long  times  of  flight, 
the  Avind  exercises  a very  disturbing  influence.  The  greater  the 
density  of  the  projectile,  the  less  will  its  motion,  during  flight, 
be  affected  by  the  wind ; and  thus  shells  ai-e  more  influenced  by 
wind  than  shot. 

The  wind  exercises  a very  great  deflecting  influence  upon  an 
elongated  projectile  during  its  flight,  rendering  it  difficult  to 
obtain  accuracy  of  fire  at  long  ranges,  even  from  rifled  guns, 
excepting  in  very  calm  weather. 

If  the  centre  of  gravity  be  placed  very  near  tlie  centre  of 
the  long  axis,  the  force  of  the  Avind  Avill  be  pretty  evenly  distrib- 
uted over  the  Avhole  length  of  the  projectile.  Should,  hoAveA^er, 
the  centre  of  gravity  be  placed  far  in  advance  of  or  beliind  the 
centre  of  figure,  the  force  of  the  wind  Avill  press  unequally  upon 
the  shot,  and  uncertain  deflections  Avill  most  probably  occur. 

821.  Yaeiable  Pkojectile-fokce. — It  is  impossible  Avith 
our  present  facilities  to  manufacture  large  quantities  of  poAvder 
of  a perfectly  uniform  quality ; but  supposing  it  could  be  ac- 
complished, the  force  from  a given  charge  Avould  be  liable  to 
variation  according  to  the  state  of  the  atmosphere,  and  the  con- 
dition of  the  poAvder  as  affected  by  the  time  it  has  been  in 
store ; it  will  also  be  frequently  found  in  practice  that  the 
charges  have  not  been  Aveighed  out  with  perfect  accuracy,  nor 
the  gun  loaded  so  that  the  projectile  is  ahvays  in  the  same  posi- 
tion Avith  reference  to  the  charge.  The  consequence  is,  that 
very  few  projectiles  fired  from  the  same  gun  Avith  Avhat  are 
called  e(pial  charges,  leave  the  bore  with  exactly  the  same  ini- 
tial velocity. 

825.  Rotation  of  the  Eaeth. — The  deviation  of  a pro- 
jectile caused  by  the  rotation  of  the  earth  is  a complicated 
problem.  The  principle  that  this  rotation  will  impress  upon 
the  projectile  a tendency,  upon  leaving  the  bore,  to  move  Avith 
the  same  velocity  in  the  same  direction  as  the  point  upon  the 
surface  from  which  the  gun  is  fired,  is  readily  comprehended, 
but  not  its  application  to  some  particular  cases.*  The  devia-' 

■*  For  a general  discussion  of  this  subject,  see  an  Article  by  Prof.  Wm. 
Ferrel  in  The  Mathematical  Monthly  for  August,  I860. 


294 


NAVAL  ORDNANCE  AND  GUNNERY. 


tion  due  to  tins  cause  is  too  sliglit  to  be  regarded  iu  prac- 
tice. 

826.  Faulty  Dispositioit  of  the  Ll\e  of  Sight. — The 
line  of  sight  may  he  improperly  placed  and  situated  out  of  the 
vertical  plane,  either  in  consequence  of  the  constnictiou  of  the 
gun  or  its  carriage,  or  hy  the  etfect  of  the  inclination  of  the 
plane  upon  which  it  is  placed.  In  these  two  cases  the  line  of 
fire  maintaining  a fixed  and  determined  position,  in  respect  to 
the  axis  of  the  gun  and  the  vertical  plane  of  fire,  the  deviations 
are  constant  for  equal  distances  and  equal  inclinations,  and  it 
becomes  easy  to  correct  them  after  a few  trials. 

827.  Influence  of  the  State  of  the  Air. — The  haro- 
raetic  state  of  the  atmosphere  may  also  produce  an  effect  upon 
the  ranges ; for  the  greater  the  density  and  elasticity  of  the 
displaced  fluid,  the  greater  will  be  the  retardation  of  the  pro- 
jectile. 

The  phenomenon  of  refraction  also  slightly  modifies  the 
range,  hut  these  last  causes  are  scarcely  appreciable  in  practice. 

828.  DEYIATIOX  OF  SPIIEEICAL  PEOJECTILES. 
— The  principal  causes  of  the  deviations  of  projectiles  fired 
from  smooth-bore  guns,  are 

1st.  Windage. 

2d.  The  imperfect  form  and  roughness  of  the  surface  of 
the  projectile. 

3d.  Eccentricity  of  projectiles  arising  from  their  not  being 
homogeneous. 

829.  Windage. — Windage  causes  irregularity  in  the  flight 
of  a projectile,  from  the  fact  of  the  elastic  gas  acting  in  the 
first  instance  on  the  upper  portion  of  the  projectile  and  di-iving 
it  against  the  bottom  of  the  bore. 

The  projectile  reacts  at  the  same  time  that  it  is  impelled 
forward  by  the  charge,  and  strikes  the  upper  surface  of  the  bore 
some  distance  in  advance,  and  so  on,  by  a succession  of  re- 


bounds until  it  leaves  the  bore  in  an  accidental  direction  and 
with  a rotatory  motion,  depending  chiefly  upon  the  position  of 
the  last  impact  against  the  bore.  (Fig.  194.) 


PEOJECTILES. 


295 


Thus,  should  the  last  impact  of  a concentric  projectile,  Avhen 
fired  from  a gun,  be  on  the  right-hand  side  of  the  bore,  as  rep  • 
resented  in  the  figure,  it  will  have  a tendency  to  deflect  to  the 
left  in  the  direction  5,  while  at  the  same  time  a rotation  will  be 
given  to  it  in  the  direction  indicated  by  the  arrows,  or  to  the 
right.  The  effect  of  this  rotation  being  to  cause  the  projectile 
itself  to  deviate  to  the  right  during  its  flight,  so  that  the  deflec- 
tion will  not  be  to  the  left,  but  to  the  right,  unless  the  range  is 
very  short. 

If  the  projectile  leave  the  gun,  rotating  on  a vertical  axis, 
with  its  forward  part  moving  from  left  to  right — supposing 
the  observer  to  be  behind  the  piece — there  will  be  a diminished 
pressure  on  the  right  side  and  an  increased  one  on  the  left  side, 
which  will  therefore  cause  it  to  deviate  to  the  right. 

If  a projectile  strike  the  bottom  of  the  bore,  the  rotation  of 
the  fore-part  would  be  from  up  downwards,  and  instead  of  de- 
flecting to  the  right,  the  range  would  be  decreased. 

Suppose  the  projectile  to  rotate  in  an  opposite  direction, 
the  results  would  be  reversed.  Should  it,  on  leaving,  strike 
any  intermediate  part  of  the  bore,  a compound  effect  would  be 
produced,  according  to  the  position  of  the  point  of  impact. 

It  appears  from  these  explanations,  that  a projectile  leaving 
the  gun,  rotating  on  any  axis,  except  one  parallel  to  that  of  the 
bore,  will  deviate  according  to  the  direction  of  the  rotation. 

830.  Eccenteicity. — Should  the  centre  of  gravity  of  a pro- 
jectile not  coincide  with  the  centre  of  figure,  it  is  termed 
eccentric,  and  is  found  to  deviate  according  to  the  position  of 
the  centre  of  gravity  when  the  ball  is  placed  in  the  bore  of 
the  gun  ; should  the  line  joining  the  centre  of  gravity  and  the 
centre  of  figure  of  a projectile  be  not  parallel  to  the  axis  of  the 
bor*e,  the  charge  of  powder  will  act  on  a larger  surface  on  one 
side  of  the  centre  of  gravity  than  on  the  other,  so  that  there 
will  be  a rotation  from  the  lightest  towards  the  heaviest  side. 

If  Fig.  195  represent  an  eccentric  shot,  the  centre  of 
gravity,  Gr,  of  which  is  below  the  centre  of  figure  F,  the  powder, 
acting  on  a larger  surface  above  than  below  G,  will  give  it  a 
rotation  as  indicated  Iry  the  arrow,  and  from  what  has  been 
previously  said,  the  deviation  will  be  to  the  side  on  which  the 
centre  of  gravity  lies ; this  is  the  ease  in  practice,  for  it  has 
been  ascertained  by  experiment  that  if  a projectile  be  placed  in 
a gun  so  that  its  centre  of  gravity  is  to  the  right  of  the  vertical 
plane  passing  through  the  axis  of  the  bore,  it  will  deviate 
towards  the  right,  and  vice-versa  ; also  if  the  centre  of  gravity 
be  upwards,  the  range  will  be  increased;  and  if  downward,  di- 
minished. 


296 


NAVAL  ORDNANCE  AND  GUNNERY. 


It  is  found  in  practice  that  projectiles  deviate  in  a curved 
line,  either  to  the  right  or  to  the  left,  the  curve  rapidly  in- 
creasing towards  the  end  of  the  range.  This  probably  occurs 


from  the  velocity  of  rotation  decreasing  hut  slightly  compared 
to  the  velocity  of  translation ; or  if  a strong  wind  is  blowing 
steadily  across  the  range  during  the  whole  time  of  its  flight, 
this  deflecting  cause  being  constant,  while  the  velocity  of  the 
projectile  diminishes,  the  curve  will  manifestly  increase  with 
the  range ; the  trajectory  is,  therefore,  a curve  of  double  curva- 
ture, its  projection  on  either  a horizontal  or  vertical  plane  be- 
ing a curved  line. 

831.  Conclusion. — From  the  foregoing  considerations  it  fol- 
lows, that  the  smoother  the  surface  of  the  projectiles  and  the 
less  their  windage  and  eccentricity,  other  things  being  equal, 
the  greater  will  he  their  accuracy.  Experiments  show  that 
the  preponderating  side  should  be  put  next  the  charge,  and. 
the  line  joining  the  centre  of  gravity  and  the  centre  of  flgure 
should  be  parallel  to  the  axis  of  the  bore. 

The  position  of  the  preponderating  side  is  found  by  float- 
ing the  projectile  in  a bath  of  mercmy,  and  the  degvee  of 
promptness  with  which  an  eccentric  shot,  floated  as  above, 
assumes  the  position  due  to  its  preponderance,  is  regarded  as 
the  measure  of  that  jireponderance. 

832.  DEVIATION  OF  ELOA^GATED  PEOJECTILES. 
— If  the  projectile  come  out  of  the  gun  perfectly  centred, 
that  is,  rotating  round  its  longest  axis,  and  having  that  axis 
coincident  with  the  line  of  flight,  there  will  be  no  tendency, 
either  of  the  axis  of  rotation,  or  of  the  projectile  itseE,  to 
deflect,  so  long  as  the  motion  is  in  a straight  line,  because  the 
resistance  of  the  air  will  act  uniformly  all  around.  As  soon, 
however,  as  the  trajectory  has  begun  to  curve  downwards  under 
the  influence  of  gravity,  the  resistance  of  the  air  acts  more 
on  the  under  side  than  on  the  upper,  and  effects  will  be  pro- 


PEOJECTILES. 


207 


duced  depending  on  tlie  resultant  direction  of  the  resistance 
of  the  air  in  relation  to  the  centre  of  gravity. 

833.  Practically,  the  path  of  the  projectile  is  found  to  re- 
sult in  a deviation,  increasing  uniformly  with  the  distance 
from  the  gun,  and  depending,  as  to  its  direction,  on  the  direc- 
tion of  the  deilectiug-force  at  the  moment  of  its  first  applica- 


tion. 

If  the  deflecting- force  act  on  the  projectile  in  a vertical 
direction  upwards,  the  horizontal  projection  of  the  line  of 
flight  will  he  a line  deviating  to  the  right  or  left,  of  the  plane 
of  Are,  according  as  the  twist  is  right  or  left  handed.  If  the 
deflecting-force  act  in  the  opposite  direction,  the  projectile 
will  he  deflected  to  the  left  or  right,  according  as  the  twist  is 
right  or  left;  and  whatever  be  the  direction  of  the  deflecting- 
force,  the  deviation  will  be  a uniformly  increasing  one  at  right 
angles  to  it. 

83d.  These  effects  may  be  illustrated  experimentally  by 
means  of  a gyroscope  provided  with  a small  elongated  projectile 
instead  of  the  disk  used  for  ordinary  experiments.  (Fig  197.) 

The  projectile  must  be  made  with 
the  greatest  care,  so  that  its  centre  of 
gravity  coincides  exactly  with  that  of  the 
two  rings  within  which  it  is  placed ; tho 
rings  are  so  arranged  that  one  can  turn 
round  a vertical  axis,  and  the  other  round  a 
horizontal  axis,  the  projectile  being  there- 
fore free  to  turn  in  any  direction.  A 
cylindrical  portion  of  metal  extends  be- 
yond the  base  of  the  projectile,  in  prolong- 
ation of  its  longer  axis,  round  which  the 
string  is  wound  to  give  the  required  rota- 
tory motion. 

As  the  projectile  in  the  gyroscope  has 
no  motion  of  translation,  a strong  current  Fig.  197. 

of  air  must  be  chrected  upon  it,  so  as  to 
represent  the  resistance  of  the  atmosphere  to  a projectile  mov- 
ing with  a high  velocity.  The  diameter  of  the  nozzle  of  the 
blower  should  be  equal  to,  or  rather  larger  than,  that  of 
projectile,  and  the  centre  of  the  blast  should  be  directed 
low  the  point  of  the  projectile  in  the  position  indicated 
E in  Fig.  145. 

835.  If  Fig.  145  represent  the  elongated  projectile  of 


the 

be- 

bj 


gyroscope,  it  will 
where  between  a 


be  found  that  a pressure,  E, 
and  h will  produce  a similar 


the 

exerted  any- 
effect  to  an 


298 


NAVAL  OEDNANCE  AND  GUNNERY. 


upward  pressure  exerted  at  tlie  point  E.  Supposing,  however, 
the  projectile  to  be  rotating  rapidly  in  the  direction  indicated 
by  the  arrow  in  Fig.  197,  and  the  pointed  end  is  facing  the 
spectator : then,  if  a pressure  be  exerted  at  5,  corresponding 
to  E in  Fig.  145,  the  point  of  the  projectile  will  not  rise  (at 
least  perceptibly),  but  will  move  laterally  in  the  direction  c,  that 
is,  to  the  right,  with  reference  to  an  observer  behind  the  gyro- 
scope ; if  a pressure  be  exerted  at  d (Fig.  197),  the  point  will 
fall ; if  at  a,  the  point  will  move  laterally  in  the  direction  c7, 
or  to  the  left,  with  reference  to  an  observer  behind  the  gvro- 
scope;  lastly,  if  a pressure  acts  upon  the  rotating  body  at  c, 
the  point  Avill  rise.  ISlow  should  a pressure  be  exerted  in  anv 
intermediate  part  of  the  circle  abed,  as,  for  instance,  between 
b and  d,  then  the  motion  of  the  point  of  the  projectile  will 
be  compounded  of  the  motions  caused  by  respective  pressures 
at  b and  d,  that  is  to  say,  the  point  Avill  move  laterally  to  the 
right  (with  reference  to  an  observer  behind  the  gyroscope), 
and  droop  at  the  same  time. 

836.  If  a strong  blast  of  air  be  directed  on  the  fore  part 
of  the  rotating  projectile,  the  centre  of  the  current  being  a 
little  below  the  point,  but  in  the  same  vertical  plane  with  it, 
as  showm  by  the  dotted  lines  in  Fig.  145,  so  as  to  represent  the 
resistance  of  the  air  to  a projectile  moving  with  a high  velo- 
city, the  pointed  end  will  first  move  slowly  to  the  right  (towards 
G,  Fig.  197),  effects  being  afterwards  successively  produced  by 
the  blast  similar  to  those  wliich  would  be  caused  by  a press- 
ure acting  gradually  round  the  circle  aebd  (Fig.  197),  as  already 
described. 

If  pressure  be  exerted  behind  the  centre  of  gravity  in- 
stead of  in  front,  or  on  the  fore  part  of  a projectile  rotating 
with  a left-handed  rotation,  the  above  effects  will  be  reversed. 

837.  The  line  of  flight  is  therefore  not  absolutely  a straight 
line,  but  becomes  a curve  of  double  curvature  ; and  if  project- 
ed on  a vertical  plane  at  right  angles  to  the  plane  of  tire, 
w'ould  consist  of  a series  of  cj’cloidal  curves,  were  the  time  of 
flight  sufficiently  great,  increasing  the  distance  of  the  ])rojec- 
tile  from  the  plane  of  fire  by  the  length  of  one  of  them  at 
each  revolution.  The  length  of  these  curves  depends  upon 
the  amount  of  the  deflecting-force,  and  their  number  is  equal 
to  the  number  of  revolutions  made  by  the  projectile  in  its 
flight. 

838.  When  an  elongated  projectile  is  fired  from  a rifle-gun, 
it  leaves  the  bore  rotating  rapidly  round  its  longer  axis  ; and  if 
the  initial  velocity  wmre  very  low,  the  projectile  experiencing  but 


PROJECTILES, 


299 


slight  resistance  from  tlie  atmosphere,  the  larger  axis  would 
remain  (as  in  vacuo)  during  the  whole  time  of  flight  parallel 
or  nearly  so  to  its  primary  direction,  as  shown  in  Fig.  198. 


In  explaining  the  effect  produced  by  the  resistance  of  the 
air  upon  an  elongated  projectile  moving  with  a high  velocity, 
tlie  projectile  will  be  supposed  to  have  what  is  termed  a right- 
handed  rotation : that  is,  the  upper  part  turns  from  left  to 
right,  with  reference  to  an  observer  placed  behind  the  gun ; 
for  the  direction  of  the  grooves  of  rifled  pieces  are  almost  inva- 
riably so  as  to  give  such  rotation. 

After  the  projectile  has  left  the  bore,  the  residtant  of  the 
resistance  of  the  air  will,  unless  the  centre  of  gravity  be  very 
far  forward,  act  upon  a point  in  front  of  the  centre  of  gravity 
and  below  the  longer  axis,  at  all  angles  of  elevation  given  in 
practical  gunnery.  The  effect  produced  by  this  pressure  will 
depend  chiefly  upon  the  form  of  the  head  of  the  projectile ; 
therefore,  let  us  first  consider  the  effect  ujion  a conoidal  head. 

839.  Deviation  of  the  Conoidal-headed  projectile. 

The  pressure  E.  (Fig.  145),  exerted  anywhere  between  a and 
h,  will  have  a tendency  to  raise  the  point  a or  to  produce  a 
similar  effect  to  an  upward  pressure  exerted  at  the  point  E. 
This  will  result  in  giving  tlie  point  a a lateral  movement  to 
the  right.  (Art  833.)  As  this  lateral  movement  of  the  point 
proceeds  so  will  the  resultant  act  more  and  more  to  the  left 
of  the  vertical  plane,  passing  through  the  longer  axis  of  the 
projectile.  And  as  the  deviation  continues  at  right  angles  to 
the  direction  of  the  deflecting-force,  the  point  will  soon  begin 
to  droop. 

The  point  of  the  projectile  first  moves  to  the  right,  then 
downwards,  still  keeping  to  the  right,  then  to  the  left,  and  so 
on,  describing  a portion  of  the  circle,  the  continuance  of  the 
motion  depending  upon  the  time  of  flight  and  velocity  main- 
tained. As  the  velocity  becomes  low,  the  circular  motion  of 
the  point  will  gradually  cease ; but  in  practice,  during  the  few 
seconds  of  flight  which  generally  elapse,  as  the  velocity  is 


300 


NAVAL  ORDNANCE  AND  GUNNERY. 


pretty  high  throughout,  there  is  prohahly  sufficient  time  and 
pressure  not  only  to  turn  the  point  to  the  right,  hut  to  bring  it 
down  on  to  the  trajectory,  or  even  below  it. 

840.  Of  course  the  longer  axis  of  an  elongated  projectile  does 
not  remain,  during  flight,  continually  a tangent  to  the  trajectory, 
unless  the  centre  of  gravity,  as  in  an  arrow  or  rocket,  is  very 
near  the  face  end  ; yet,  practically,  on  account  of  the  drooping 
of  the  point,  the  longer  axis  may  throughout  a considerable 
portion  of  the  time  of  flight  approximate  very  nearly  to  a tan- 
gent to  the  trajectory,  as  in  Fig.  199, 


Fig.  199. 


The  effects  on  targets  furnish  most  satisfactoiy  evidence  of 
this  ; it  is  almost  invariably  found  that  the  holes  made  in  targets 
are  circular,  even  when  elongated  jirojectiles  descend  at  consid- 
erable angles. 

The  most  probable  explanation  of  this  fact  must  evidently 
be,  that  the  point  of  the  projectile  has  drooped  during  flight,  so 
that,  on  striking  the  longer  axis  is  nearly  perpendicular  to  the 
plane  of  the  target.  (Fig.  199.) 

This  drooping  of  the  point  is  of  importance,  fordid  the  axis 
remain  parallel  during  flight  to  its  primary  direction,  the  pro- 
jectile would  most  probably,  when  fired  at  any  hut  a very  low 
angle,  on  striking  an  object  of  hard  material  and  solid  structure 
turn  up  against  it  lengthways,  and  therefore  produce  but  trifling 
effect.  This  has  not,  however,  been  found  to  take  place  in 
practice,  but  on  the  contrary  the  penetration  of  elongated  pro- 
jectiles at  considerable  ranges,  are  always  remarkably  great. 
There  is  little  fear  of  the  projectile  turning  up  against  an  object 
unless  the  velocity  of  translation  and  rotation  be  very  low,  and 
the  angle  of  fire  very  high. 

841.  Deviation  of  tlie  Flat-headed  Projectile. — A pressure  ex- 
erted upou  the  head  and  below  the  larger  axis,  as  (K  Fig.  146), 
will  have  a tendency  to  cause  the  head  to  droop  ; or  will  produce 


PEOJECTILES. 


301 


an  effect  similar  to  a downward  pressure,  acting  at  C ; just  the 
opposite  of  what  is  observed  with  a conoidal-pointed  projectile. 

Therefore  (Art.  833),  the  projectile  will  he  deflected  to  the 
left  or  right,  according  as  the  twist  is  right  or  left  handed. 

It  is  found  in  practice  that  conoidal-headed  projectiles  fired 
from  rifled  guns  giving  a right-handed  rotation,  always  deviate 
to  the  right ; and  in  the  few’  cases  tried  with  guns  giving  a left- 
handed  rotation,  the  deviation  is  to  the  left ; wdth  flat -headed 
projectiles,  these  deviations  are  reversed. 

812.  Drift. — This  peculiar  deviation  is  called  drift.,  and  is 
generally  constant  for  the  same  ranges — so  that  it  can  he 
allow’ed  for  in  pointing  the  gun,  hy  using  a horizontal  slide  grad- 
uated and  attached  to  the  tangent  scale,  or  by  inclining  the  tan- 
gent scale  to  the  left. 


Section  III.— Effects. 

813.  General  Considekation. — A knowledge  of  the  de- 
structive effects  of  projectiles  is  of  very  great  importance.  In 
general,  these  effects  depend  upon  a variety  of  circumstances, 
such  as  the  velocity  of  the  projectile  at  the  moment  of  impact, 
its  weight,  form,  diameter,  the  material  of  which  it  is  made,  the 
nature  of  the  object  struck,  and  the  relative  position  of  this  lat- 
ter with  regal’d  to  the  trajectory  of  the  projectile. 

When  a projectile  strikes  an  object,  its  energy  is  expended, 
not  only  in  penetrating,  fracturing,  or  producing  vibration  in 
the  material -of  the  object,  but,  when  the  latter  offers  great  re- 
sistance, in  breaking  up  or  changing  the  form  of  the  projectile. 

841.  Ijipact  of  Projectiles. — In  order  to  arrive  at  a clear 
understanding  of  Avhat  takes  place  when  the  motion  of  a projec- 
tile is  arrested  by  any  resisting  medium,  it  is  necessary  to  recall 
some  of  the  elementary  prmciples  upon  which  these  phenomena 
depend.* 

The  manner  in  which  a projectile  acquires  its  velocity,  is  a 
good  illustration  of  the  manner  in  which  its  motion  is  de- 
stroyed. 

If  the  mean  pressure,  P,  of  the  gas  be  multiplied  by  the 
space,  S,  passed  over  by  the  projectile  while  acquu’ing  its  veloc- 
ity, the  result  will  be  the  measure  of  the  work  done  by  the 
charge  of  powder ; and  it  will  also  be  equal  to  thp  work  of 
stopping  the  same  projectile,  no  matter  how  or  by  what  means 
it  may  be  brought  to  rest. 


King. 


302 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  same  result  is  generally  arrived  at  by  measuring  the  veloc- 
ity imparted  to  the  projectile  under  the  circumstances  men- 
tioned, and  multiplying  the  square  of  the  velocity  by  one-half 
of  the  mass  of  the  projectile  ; or,  since  the  mass  is  equal  to  the 
weight  divided  by  the  force  of  gra^nty,  the  expression  for  the 
work  stored  in  the  projectile,  and  which  must  be  expended  in 
AV  v“ 

bringing  it  to  rest,  = — ^ — , where  W = weight  of  the  projec- 

tile  in  pounds,  v velocity  of  the  projectile  in  feet,  and  g = the 
force  of  gravity  in  feet,  or  the  velocity  which  a body  will  ac- 
quire by  its  own  weight  in  one  second  of  time. 

This  expression  involves  indirectly  the  same  quantities  as 
that  first  mentioned  ; namely,  the  mean  pressure  of  the  gas  and 
the  distance  passed  over  bj'^  the  projectile  ; assuming  this  meas- 
ure for  the  work  stored  in  the  projectile,  it  remains  to  consider 
how  this  work  is  expended. 

84:5.  The  following  are  the  different  effects  produced  by  the 
impact  of  a projectile  upon  any  solid  body  ; some  of  these  being 
so  connected  as  to  render  their  relative  importance  extremely 
doubtful. 

Comjpression. — The  first  effort  of  impact  is  to  compress  or 
drive  back  those  portions  of  both  projectiles  and  target  first 
coming  in  contact  upon  those  immediately  behind  them ; the 
amount  of  this  compression  depending  upon  the  material  and 
velocity  of  impact,  as  well  as  upon  the  form  of  the  projectile. 

Elongation. — The  greater  part  of  the  work  of  the  pro- 
jectile in  penetrating  wrought-iron  and  similar  materials 
is  expended  in  overcoming  the  tenacity  of  the  material,  or  in 
elongating  the  fibre.  This  is  evident  when  we  consider  that 
punching  or  shearing  consists  not  so  much  in  cutting  the  fibre, 
as  in  bending  it,  and  afterwards  pulling  it  in  two  lengthwise. 

Shearing. — This,  as  just  stated,  consists  chiefly  in  the  two 
strains  already  mentioned. 

Bending. — This  also  implies  tension  and  compression  ; the 
back  of  the  target  being  elongated,  and  the  front  compressed. 

Pulverizing — a portion  of  the  material.  This  takes 
place  only  in  case  of  hard  materials,  as  stone  or  cast-iron,  and  it 
then  absorbs  a very  great  amount  of  work.  Like  bending  and 
shearing,  it  involves  compression  and  elongation,  the  material 
being  compressed  until  it  yields  laterally  to  a tensile  strain. 

Motion. — While  the  work  is  being  expended,  a certain 
amount  of  time  is  allowed  for  the  force  of  the  projectile  to  im- 
part motion  to  the  target,  especially  that  portion  immediately 
in  front  of  the  projectile. 

Friction.  — T\\q  friction  is  very  great,  especially  in  the  case 


PROJECTILES. 


303 


of  the  more  pointed  form  of  projectile,  and  varies  inversely 
with  the  velocity  of  the  projectile. 

Heat. — This  is  due  to  friction,  both  external  and  internal, 
that  is,  of  the  projectile  and  fragments  against  the  target,  and 
against  each  other  during  the  distortion  of  the  material,  from 
compression,  bending,  etc. 

The  suddenness  with  which  this  heat  is  generated  is  almost 
unequalled  by  any  known  source  of  heat.  It  is  well  known  that 
the  heat  developed  in  the  interior  of  loaded  shells,  on  striking 
violently  a thick  iron  plate,  is  sufficient  to  ignite  the  powder, 
and  this  fact  has  been  utilized  in  dispensing  with  fuzes  for  ex- 
ploding armor-punching  shells. 

The  effect  of  a projectile  on  striking  a mass  or  target  of  any 
form  or  material,  may  be  divided  into  two  general  portions,  one 
being  entirely  local,  while  the  other  is  distributed  over  more  or 
less  surface  according  to  circumstances. 

The  former  is  penetration.^  and  the  latter  may  be  called 
the  concussion. 

816.  PENETRATIOlSr. — General  Theory. — The  most 
common  substances  encountered  by  projectiles  are  arranged  in 
the  following  series,  in  the  order  of  their  resistances  to  penetra- 
tion : — water,  sand,  wood,  lead,  copper,  wrought-iron,  soft 
steel,  cast-iron,  chilled  iron,  hardened  steel,  etc.  All  other  sub- 
stances may  be  arranged  between  these,  or  in  continuation  of 
the  series. 

Air  opposes  the  motion  of  a projectile  by  its  inertia,  elastic 
force,  and  the  pressure  due  to  its  weight.  The  projectile  com- 
presses the  air  in  its  front  and  disperses  it  laterally,  while  the 
rear  of  the  projectile  is  relieved  by  its  motion  of  the  normal 
pressure  of  the  air.  A small  amount  of  resistance  is  also  met 
with  in  the  shape  of  friction. 

Water. — In  the  case  of  water  these  resistances  are  increased 
by  the  greater  density  and  weight  of  this  substance,  and  there 
is  also  a slight  additional  resistance  due  to  the  cohesion  among 
the  particles. 

Sand,  being  a solid,  or  at  least  made  up  of  solid  elements, 
presents  the  additional  resistance  of  crushing-strength.”  It 
cannot  be  penetrated  at  a high  velocity  without  crushing  some 
of  the  grains,  and  the  higher  the  velocity  the  greater  the 
amount  of  Avork  expended  in  this  manner.  This  resistance  to 
crushing  implies  a continuation  of  the  elastic  force  beyond  the 
elastic  limits,  and  involves  indirectly  tensile  strength,  since  a 
solid  in  being  crushed  must  enlarge  laterally  and  finally  yield 
to  a strain  of  tension. 

Wood. — In  penetrating  wood,  lead,  or  any  of  the  other 


304 


NAVAL  ORDNANCE  AND  GUNNERY. 


materials,  “tensile  strength ” forms  the  chief  element  of  the  re- 
sistance, while  inertia  and  friction  become  of  minor  importance. 

847.  J^asticity. — The  office  of  elasticity  in  all  these  cases 
is  to  transmit  the  effect  of  the  projectile  from  those  particles 
first  acted  upon  to  those  more  remote,  and  thus  calling  into 
play  their  inertia  or  tensile  strength,  as  the  case  may  he  ; and 
were  it  not  for  this  property,  the  statical  resistance  of  a plate 
of  any  material  to  perforation  Avould  be  entirely  independent  of 
the  thickness  of  the  plate  ; a thick  plate  would  offer  no  greater 
resistance  than  a thin  one,  since  each  layer  or  unit  of  thickness 
would  be  perforated  AAuthout  receding  any  assistance  from  its 
neighbors. 

The  worh  of  penetration  woiild  then  vary  directly  with  the 
distance  penetrated,  or  the  thickness  of  the  plate;  elasticity, 
however,  has  its  maximum  point  of  usefulness  in  resisting  pen- 
etration, and  beyond  this  it  becomes  a great  disad^'antage. 
While  increasing  the  number  of  fibres  or  elementary  portions 
of  the  material  broken  at  once,  thereby  increasing  the  statical 
resistance,  it  diminishes  the  time  dxiring  Avhich  this  resistance 
opposes  the  motion  of  the  projectile  in  like  ratio;  and  the 
amount  of  motion  destroyed  or  generated  increases  with  the 
time  as  Avell  as  Avith  the  force  or  resistance.  For  this  reason 
hardened  steel  and  chilled  iron  are  less  efficient  in  stopping 
projectiles  than  soft  iron,  although  they  offer  a much  greater 
statical  resistance  to  penetration. 

There  are  many  reasons  for  helieAung  that  a general  for- 
mula for  the  penetration  of  projectiles  in  all  materials  may  be 
deduced,  Avhen  experiments  have  been  sufficiently  extended,  in 
Avhich  tlie  constants  will  simply  require  changing  to  suit  any 
particular  case  under  consideration. 

848.  Peneteation  of  Spherical  Projectiles. — The  area 
presented  by  a ball  may  be  taken  as  equal  to  that  of  its  great 
circle ; if,  then,  R = the  mean  resistance  per  square  inch 
offered  by  the  object  throughout  the  penetration,  and  r = the 
radius  of  the  shot, 

R 7t  =z  resistance  to  he  overcome  by  shot — the  formula 
for  accumulated  worlc  being ; 

and  putting  y?  for  S,  the  space  penetrated 


P.S  = 
P = 


PEOJECTILES. 


305 


_ 

Let  d = weight  of  a cubic  inch  of  the  materia]  of  the  shot ; 

then  w = ^7tT^d, 

, . rrd  d'o  'irdv^ 

This  formula,  although  answering  for  low  velocities,  gives 
too  great  penetration  for  high  velocities ; it  is,  however,  sufB- 
ciently  accurate  for  the  deduction  of  the  simple  laws  stated 
below. 

R,  which  will  vary  with  the  nature  of  the  material  fired  at, 
whether  wood  or  masonry,  or  other  substances,  must  be  found 
by  experiment. 

'When  the  resisting  material  is  the  same, 

P varies  r d 

or  the  penetration  is  proportioned  to  the  diameter  and  density 
of  tire  sliot,  and  to  the  square  of  its  velocity  on  impact — so 
that  the  larger  the  diameter  of  the  ball,  and  the  greater  its 
density,  the  deeper  will  be  the  penetration ; especially  as  the 
final  velocity  for  the  same  initial  velocity  will  be  higher. 

When  projectiles  of  the  same  density  are  fired  into  the 
same  material, 

P varies  as  r v‘‘, 

or  with  the  diameter  of  the  shot  and  the  square  of  its  velocity 
on  impact.^ 

8-19.  Peneteation  of  Elongated  Pkojectiles. — The  pen- 
etration of  an  elongated  projectile  is  greater  than  that  of  a 
spherical  projectile  of  equal  weight,  when  both  are  fired  with 
the  same  initial  velocity  ; for  the  former  presents  a less  area  to 
the  resistance  of  the  object;  it  can  have  a pointed  head,  and  it 
will  have  a greater  final  velocity,  being  less  retarded  during 
flight. 

In  general,  however,  an  elongated  projectile  is  fired  with  a 
lower  initial  velocity  than  a spherical  projectile  of  equal  weight 
from  a smooth-bore  gun  ; and,  therefore,  at  a short  distance, 
the  latter  will  most  probably  produce  more  effect  as  regards 
penetration  than  the  former  ; but  as  the  range  is  increased,  so 
will  the  penetrating  power  of  the  elongated  projectile  be 
greater  conqrared  with  that  of  the  spherical,  for  the  former  will 
maintain  a high  velocity  much  longer  than  the  latter. 

850.  Formula  for  Perforation  of  Iron  Plates. — One  of 
20 


306 


NAVAL  ORDNANCE  AND  GUNNERY. 


tlie  first  questions  to  present  itself  in  connection  with  annor- 
plating  is  the  relation  between  the  thickness  of  the  plate  and 
the  diameter,  Aveight,  and  velocity  of  the  projectile  recpiired  to 
perforate  it ; or,  having  given  the  diameter,  weight,  and  veloc- 
ity of  a projectile,  required  the  thickness  of  a single  wrought- 
iron  plate  which  it  will  just  perforate. 

Several  formulre  have  been  proposed  for  this  purpose,  but 
the  great  ditficulty  has  been  the  want  of  experimental  results 
sufficiently  accurate  and  comprehensive  to  verify  the  principles 
upon  which  they  are  based  ; and  to  give  the  correct  values  for 
the  constants  or  co-efficients  Avhich  enter  them.  Captain  I^oble, 
li.  A.,*  gives  the  following  formula  for  the  penetration  of 
wrought-iron  plates  by  steel  shot,  the  impact  being  direct : 

= 27rE/r5\  Avhere 

^ . 

W = weight  of  shot  in  pounds, 

-y  = velocity  on  impact,  in  feet, 
g — the  force  of  gravity, 

2E.  :=:  diameter  of  shot  in  feet, 

1)  — thickness  of  unbacked  plate  in  feet, 

= a coefficient  depending  on  the  nature  of  the 
AAwought-iron  in  the  plate,  and  the  nature  and 
form  of  head  of  the  shot. 

Solving  the  above  equation  for  J,  giA^es  : 


In  order  to  determine  h the  following  series  of  equations 
can  be  formed : 


The  variable  quantities  in  these  equations  are  E,  5,  w,  and  r ; 


* ‘ ‘ Report  on  various  experiments  carried.out  under  the  direction  of  the  Ord- 
nance Select  Committee,  relative  to  the  penetration  of  iron-armor  plates  by 
steel  shot.”  By  Capt.  W.  H.  Noble,  R.  A.  London : I860. 


and  for  /o, 


^ 47rlvv/Z»' 


^Tt^gjVh  — W,Aq'‘  =r  0. 
47rR„y5"Z;  — W„a'„‘  = o. 
4:7tYv,gh-k  — = o. 

etc.,  etc.,  etc. 


I 


PROJECTILES.  307 

7t  being  tbe  usual  representative  of  the  ratio  of  diameter  to  cir- 
cumference of  the  circle,  and  g representing  the  force  of  grav- 
ity in  dynamical  terms. 

Having  determined  the  value  of  Tc,  the  “ work  ” necessary 
to  penetrate  any  unbacked  plate  of  given  thickness  may  be 
calculated. 

This  formula  is  only  claimed  to  give  a near  approximation, 
as  the  case  is  one  which  does  not  admit  of  absolute  accimacy, 
involving,  as  it  does,  many  sources  of  error  and  uncertainty, 
which  it  is  impossible  to  eliminate  without  an  almost  intermin- 
able series  of  experiments. 

851.  Fokm  of  Head. — That  the  penetration  of  an  elon- 
gated projectile  is  influenced  by  the  form  of  its  head  has  been 
shown  by  experiment,  many  clifEerent  forms  of  head  having 
been  tried.  The  flat  head  has  been  strongly  advocated,  because 
it  is  asserted  to  be  a better  form  for  pimching  than  any  of  the 
pointed  heads,  and  because  it  is  also  asserted  that  it  will  bite 
into  an  iron  plate  at  such  an  oblique  angle  as  would  cause  a 
pointed  head  to  merely  glance.  But  the  truth  of  these  asser- 
tions has  not  been  generally  admitted.  The  flat-headed  projec- 
tile is  objectionable  both  as  regards  accuracy  and  velocity,  and 
it  has  also  a tendency  to  upset  or  bulge  at  the  head  on  impact, 
and  this  result  is  very  marked. 

The  pointed  projectile  is  superior  in  accuracy  and  range, 
and  does  not  upset  on  impact  to  anything  like  the  same  ex- 
tent. 

It  is  asserted  that  it  cuts  through  an  iron  plate  to  a better 
advantage,  or  rather  tears  through  blending  back  the  plate. 

852.  OijLiQUE  Impact. — -Another  point  in  connection  with 
the  penetration  of  elongated  projectiles  is  the  effect  of  different 
forms  of  head  upon  the  rotation  of  the  projectile  when  the  im- 
pact is  oblique. 

If  the  axis  of  the  projectile  is  tangent  to  the  trajectory  on 
impact,  and  at  the  same  time  normal  to  the  target,  there  will 
be  no  tendency  to  rotate  about  any  axis  parallel  with  the  plane 
of  the  target.  In  Fig.  200,  if  we  suppose  a projectile  to  arrive 
at  A,  under  these  conditions  it  will  undoubtedly  penetrate  the 
plate  directly.  But  let  one  arrive  at  D or  E,  and  there  will  be 
a tendency  to  rotate,  and  this  tendency  will  depend  upon  the 
form  of  the  projectile  as  well  as  upon  the  angle  between  the 
trajectory  and  its  axis. 

Now  it  is  asserted,  on  the  one  hand,  that  the  advantage  in 
the  latter  case  will  be  in  favor  of  the  flat-headed  projectile,  since 
the  moment  of  the  rotating  force  will  be  the  variable  resistance 
of  the  plate  multiplied  by  the  lever  arm  Dd,  for  the  pointed 


308 


NAVAL  OEDNANCE  AND  GUNNERY. 


projectile,  and  the  same  multiplied  hy  a much  shorter  lever 
arm,  Ee,  in  case  of  the  flat-headed  projectile,  and  this  may  be 
negative ; or  in  other  words,  there  may  be  a tendency  to  rotate 


towards  the  normal,  which  would  be  a decided  advantage.  This 
would  take  place  when  the  line  of  the  trajectory  passed  within 
the  base  of  the  shot. 

In  the  third  case,  represented  at  B and  C,  a projectile  is 
moving  with  its  axis  tangent  to  the  trajectory,  but  oblique  to  the 
target ; here  there  is  also  a tendency  for  the  flat-headed  projec- 
tile to  rotate  toward  the  normal,  but  it  is  questionable  whether 
such  rotation  would  be  advantageous.  The  pointed  projectile 
would  have  a less  tendency  to  such  rotation. 

On  the  other  hand  the  respective  motions  of  a flat  and 
pointed  headed  projectile  on  oblique  impact  are  explained  as 
follows  : It  is  asserted  that  the  flat-headed  projectile  on  striking 
(Fig.  201),  cuts  out  a portion  of  the  face  of  the  plate,  which  it 
carries  along  in  front,  thus  increasing  the  thickness  to  be  pen- 
etrated, and,  remaining  nearly  parallel  to  its  original  direction, 
it  has  to  pass  through  the  plate  obliquely. 

While  if  the  projectile  has  a pointed  head  (Fig.  202),  the 
point  enters  at  flrst  more  deeply  into  the  plate  than  the  flat 
head,  and  the  centre  of  gravity  moving  forward,  the  projectile 
turns  around  more  readily  than  with  the  latter,  so  that  its  axis 
becomes  perpendicular,  or  nearly  so,  to  the  face  of  the  plate, 
having  then  only  the  least  thickness  to  penetrate. 

It  is  ditficult  to  obtain  for  comparison  the  results  of  practice 
with  the  flat  and  pointed  headed  projectiles  of  the  same  mate- 
rial tired  at  targets  inclined  to  the  line  of  the  range  ; the  former 
having  been  so  little  used,  as  its  form  is  so  objectionable,  both 
as  regaixls  accuracy  and  velocity. 

On  the  whole  it  may  be  said  that  in  the  case  when  the  pro- 


PEOJECTILES. 


309 


jeetile  onglit  to  be  capable  of  piercing  tbe  plate  or  target, 
there  is  little  difference  between  the  effect  of  a flat  head  and  a 
hemispherical  head ; but  when  the  target  is  beyond  the  power 


of  the  projectile,  the  hemispherical  head  makes  the  deepest 
indent. 

853.  Concussion. — The  impact  of  a projectile,  in  addition  to 
indenting  or  penetrating  a target,  produces  more  or  less  bend- 
ing, tearing,  and  other  damage  at  a distance  from  the  point  of 
impact ; which  effects  may  be  classed  under  the  term  “ Con- 
cussion.” 

The  effect  of  concussion  is  transmitted  from  the  point  of  im- 
pact in  all  directions,  in  the  same  manner  as  sound-waves  and  in- 
creases with  the  elasticity  of  the  material.  Whatever  tends  to 
diminish  the  elasticity  of  the  structure,  as  dividing  it  into  many 
pieces,  or  using  soft  ductile  material  to  receive  the  projectile,  will 
diminish  the  effect  of  concussion.  This  effect  is  expended  in 
two  ways : 

First,  in  giving  motion  to  the  structure  or  in  developing 
inertia  ; and,  second,  in  overcoming  the  tenacity  of  the  material, 
either  in  bending  or  tearing  those  portions  first  acted  upon  from 
those  more  remote. 

Both  of  these  components,  increase  with  the  whole  amount 
of  work  expended  by  the  projectile,  other  conditions  being 
equal. 

The  first  component,  being  motion  converted  into  motion,  is 
nearly  independent  of  the  amount  of  penetration  ; it  would  be 
absolutely  independent  but  for  the  fact  that  where  the  penetra- 
tion is  very  slight  the  projectile  or  pieces  of  it  may  be  thrown 


Fig.  201 


Fig.  202. 


810 


ITAVAL  ORDNANCE  AND  GUNNERY. 


to  the  ]-eai’  by  the  elasticity  of  the  target,  and  this  effect,  re-act- 
ing upon  tlie  target,  vrould  be  in  addition  to  that  due  to  the  stop- 
ping of  the  projectile.  Taking  an  extreme  case,  suppose  the 
target  and  projectile  to  be  perfectly  elastic,  and  to  resist  all  pen- 
etration ; the  projectile  would  be  thrown  to  the  rear  with  nearly 
the  velocity  with  which  it  struck,  and  the  velocity  imparted  to 
the  target  woidd  be  double  what  it  would  have  been  had  the 
target  and  projectile  been  perfectly  inelastic. 

The  second  component  will  increase  as  the  amormt  of  pene- 
tration diminishes,  since  the  less  the  penetration,  the  greater 
must  be  the  force  exerted  by  the  structm*e  to  absorb  a given 
amount  of  work  from  the  projectile.  But  the  amount  of  pene- 
tration for  the  same  form  of  projectile,  and  with  other  condi- 
tions equal,  diminishes  nearly  as  the  diameter  of  the  projectile 
increases ; and  since  the  work  stored  in  a projectile  va- 
ries directly  with  its  weight,  or  the  cube  of  the  diameter,  we 
may  conclude  that  that  xjortion  of  the  effect  of  concussion  ex- 
pended in  overcoming  the  cohesion  of  the  material  varies  di- 
rectly with  the  fourth  power  of  the  diameter  of  the  projectile  / 
on  this  supposition  this  effect,  for  the  X,  XA^,  and  XX  inch 
spherical  shot,  would  be  as  1,  5 and  16,  respectively,  while  the 
relative  penetration  of  these  projectiles  would  be  only  about 
as  1,  1-|-,  and  2. 

The  same  effect  may  also  be  shown  to  vary  directly  with 
the  velocity  of  impact.  For  a given  amount  of  work  expended 
by  the  projectile,  it  is  evident  that  the  lower  the  velocity,  or 
the  longer  the  time  allowed  for  the  force  or  resistance  of  the 
target  to  work,  and  the  concussion  to  be  transmitted  to  distant 
points,  the  greater  will  be  the  effect  in  bending  the  target, 
breaking  bolts,  and  otherwise  shattering  the  structure ; but  the 
whole  work  arises  with  the  square  of  the  velocity,  and  this, 
divided  by  the  velocity,  leaves  the  first  power  of  the  velocity 
as  before  stated. 

The  form  of  projectile  is  supposed  to  be  the  same  in  all 
cases. 

The  effect  of  changing  the  form  would  depend  upon  the 
change  in  penetration,  those  forms  which  give  the  greatest  pene- 
tration giving  the  least  effect  of  concussion. 

854.  Aemoe-piekcing  Projectiles.* — Projectiles  intended 
for  practice  at  objects  composed  of  Avood,  masonry,  or  earth, 
are  made  of  cast-iron,  but  since  the  introduction  of  iron  for  the 
defence  of  ships  and  fortifications,  a material  possessing  greater 
hardness  than  ordinary  cast-iron  is  required  to  overcome  the 
resistance  opposed  by  thick  wrought-iron  plates.  Both  elou- 

* Mallet. 


PROJECTILES. 


311 


gated  and  spherical  projectiles  for  use  against  armor  should  he 
of  the  hardest  and  toughest  material  possible. 

The  power  of  a projectile  to  stand  up  to  its  work  and  de- 
liver its  full  blow  on  the  target  depends  on  the  shape  as  much 
as  on  the  quality  of  the  metal  of  which  it  is  composed. 

855.  Shape. — Spherical  Projectiles. — The  resistance  of  the 
plate,  neglecting  friction,  acts  as  a normal  to  each  point  of  the 
surface  of  contact  of  the  projectile ; thus,  in  Fig.  203  it  will  be 
seen  that  the  portion  of  a spherical  projectile  included  be- 
tween A and  B,  which  we  may  term  the  zone  of  compression, 
is  subject  to  a crushpig  pressure  towards  the  centre,  O,  but  it 
may  be  said  to  be  under  no  tensile  strain.  While  the  posterior 
portion  of  the  projectile  is  suddenly  cheeked  by  it  in  the  form 
of  a wedge,  when  a portion  of  the  work  stored  up  in  it — (the 
amount  depending  on  the  tensile  strength  of  the  material  of  the 
projectile) — is  im- 
pressed on  the  tdrget 
through  the  front  por- 
tion, A O B,  while 
the  remainder  is  car- 
ried off  unprofitably 


in  the  fragments  into 
which  the  posterior 
portion  breaks. 

On  examining  the 
projectile  after  im- 
pact, a part  very 
nearly  corresponding 
to  A 0 B in  form, 
will  be  found  intact 
(Fig.  203),  with  the 
fractured  surface 
scored  and  polished, 
while  the  remainder 
will  be  dispersed  in  small  fragments. 

We  know  that  any  casting  fractures  most  easily  in  the  direc- 
tion of  a normal  to  its  surface,  the  crystals  settling  themselves 
so  as  to  form  lines  on  this  direction. 

Theoretically,  the  portion  represented  by  Fig.  203  ought 
to  be  smaller  as  the  penetration  is  less — except  in  the  case  of 


Fig.  203. — Anterior  Fragment  of  round  shot 
after  impact  against  armor  coinciding  nearly 
■with  zone  of  compression. 


the  entire  blow  being  too  small  to  overcome  the  tensile  streugth 
of  the  metal  in  the  manner  described : — when  the  projectile 
woidd  only  split  irregiilai'ly  or  in  an  extreme  case  remain 
entire. 

In  all  instances,  obviously  a great  amount  of  tlie  work 


312 


NAVAL  OKDNANCE  AND  GUNNBET. 


Stored  np  in  the  projectile  is  wasted ; not  that  actually  em- 
ployed in  breaking  it,  for  such  work  is  clearly  the  result  of  the 
reaction  from  the  target ; hut  whatev^er  power  remains  stored 
up  in  the  fragments,  after  they  sever  themselves  from  the  mass 
of  the  projectile. 

Since  it  is  impossible  to  predict  what  part  of  a spherical 
projectile  fired  from  a smooth-bore  gun  will  come  in  contact 
with  the  target  on  impact,  it  is  necessary  that  the  material 
should  be  such  as  will  offer  the  greatest  union  of  hardness, 
crushing-strength,  and  tenacity ; therefore  steel  has  been  re- 
sorted to  in  some  instances,  and  may  be  regarded  as  the  cul- 
minating point  of  development  of  the  smooth-bore  projec- 
tiles. 

856.  Elongated  Projectiles. — The  flat-ended  form  possesses 
a peculiar  advantage  as  regards  the  projectile,  and  another  as 

concerns  the  plate. 

As  to  the  projectiles, 
it  may  be  seen  (Fig.  204:) 
that  in  direct  impact  the 
whole  of  the  resistance 
of  the  target  acts  in  lines 
j>arallel  to  the  projectile’s 
axis,  which  direction  is 
the  most  favorable  to  the 
projectile  retaining  its 
mass  and  delivering  its 
full  blow  on  the  target, 
and  again,  if  the  target 
is  to  be  punched  by 
actual  shearing,  the  flat- 
head  is  the  form  best  adapted  to  effect  it. 

The  flat-head  would  probably  be  best  in  the  case  of  direct 
firing  against  plates  composed  of  hard  iron,  for  it  is  easy  to 
conceive  of  a hard  material  offering  very  great  resistance  to  the 
forcing  open  of  a pointed  head,  which  might  be  punched  by 
the  clean  shearing  of  a flat-headed  projectile. 

857.  The  power  given  by  rotation,  of  keeping  the  same 
portion  of  a projectile  presented  to  the  front,  is  of  peculiar 
value  in  punching  armor-plates ; it  enables  the  head  of  a pro- 
jectile to  he  made  of  any  desired  form,  while  the  power  of  re- 
diicing  the  calibre  of  a projectile  in  proportion  to  its  weight, 
which  is  perhaps  the  principal  advantage  obtained  by  rifling,  is 
also  most  important  here,  the  depth  of  penetration  being  in  in- 
verse proportion  to  the  circumference. 

858.  In  shells,  however,  this  stability  of  the  axis  of  rotation 


PEOJECTILES. 


313 


tells  more  fully,  for  it  enables  every  part  of  the  projectile  to  be 
made  of  such  proportions  as  will  give  the  maximum  power  at 
the  moment  of  impact.  The  walls  of  an  elongated  shell  being 
chiefly  subjected  to  a longitudinal  strain,  an  interior  hollow 
may  be  made  without  entailing  the  great  weakness  existing  in 
spherical  shells  as  compared  wdth  solid  shot.  Hence  it  follows 
that  while  smooth-bore  shells  have  seldom  or  never  been  fired 
at  armor,  rifled  shells  have  proved  very  successful. 

859.  There  are  two  causes  which  contribute  to  give  shells 


peculiar  power  against  iron  plates. 

The  first  is  that  it  is  not  necessary  to  weaken  the  head  of  a 
shell  by  making  a fuze-hole  in  it ; because  no  fuze  is  reqirired, 
the  heat  generated  on  the  impact  of  a projectile  against  the 
armor  being  sufficient  to  fire  the  bursting-charge.  To  such  an 


extent  ]s 


light 


as  well  as  heat  generated,  that  on  firing  at 


target  after  dark,  a pale  flash  is  seen  to  follow  the  impact. 

The  second  cause  that  operates  to  favor  the  action  of  shells, 
is  the  fact  that  when  the 
shell  has  penetrated  to  a 
depth  of  even  a few  inches 
before  rupture  occurs,  the 
sides  are  supported  by  the 
armor  around  them,  and  the 
explosion,  being  confined  at 
the  sides,  acts  to  the  front 


with  greatly  increased  force. 

860.  In  a conical  head 
(Fig.  205),  the  normal  pres- 
sures throughout  form  a 
zone  of  compression  acting 
as  a wedge  towards  the  body 
of  the  projectile,  whose  angle 
is  the  supplement  of  that  of 
the  cone  of  the  head.  This  is  better  than  that  formed  in  the 
spherical  head,  because  the  angle  is  less  acute,  and  because  the 
apex  of  the  wedge,  instead  of  being  a fixed  point  throughout 
(the  centre  of  the  sphere),  moves  along  the  axis  of  the  projectile 
as  it  enters  deeper  and  deeper  into  the  target. 

In  the  ogival  head  (Figs.  206  and  207),  it  will  easily  be  seen 
how  much  superior  is  the  action.  In  this  the  wedge"  is  at  the 
commencement  slightly  acute,  but  then  the  resistance  acts  on  a 
small  surface  and  is  comparatively  small,  and  the  angle  in- 
creases, till,  at  the  junction  of  head  and  body,  it  becomes  180°, 
or  a straight  line  (Fig.  207),  so  that  we  then  have  the  body  of 
the  projectile  in  much  the  same  condition  as  the  flat-hea"ded 


314 


NAVAL  ORDNANCE  AND  GUNNERY. 


bolt  driving  before  it  an  ogival  wedge,  winch  opens  the  armor 
by  wedging  rather  than  by  clipping  or  pnnching, 

861.  It  is  possible,  no  doubt,  to  conceive  of  a material  that 


might  be  sheared  by  the  flat  projectile  more  easily  than  opened 
by  the  ogival ; but  it  would  be  to  contradict  the  results  of  ex- 
perience to  say  that  plate-iron  was  such  a substance  ; and  as  the 
softer  and  more  plastic  natures  of  plate-iron  have  been  found  to 
hold  their  bolts  the  best,  and  stand  the  longest,  and  so  have 
been  universally  adopted,  the  ogival  has  become  obviously  the 
correct  form  of  head. 

8G2.  The  Effect  of  Haedexixg  Pkojectiles  is  probably 
much  greater  than  is  generally  supposed ; that  is,  the  amount 
of  work  gained  is  much  greater  than  the  increase  of  strength 
of  the  projectile. 

It  is  well  known  that  a very  small  force  may  under  certain 
circumstances  determine  the  performance  or  non-performance 
of  a very  large  amount  of  work.  In  like  manner  a very  slight 
addition  to  the  rigidity  of  a projectile,  by  hardening  or  other- 
Avise,  may  deteianine  Avhether  a very  large  amount  of  Avork 
shall  be  Avasted  upon  the  projectile  or  expended  upon  the 
plate. 

863.  Another  means  of  increasing  the  work  done  upon  the 
armor-plate  in  comparison  Avith  that  done  ipmn  the  projectile 
is  by  increasing  the  velocity  of  the  latter.  That  is,  a projectile 
moving  at  a Ioav  A’elocity  may  be  smashed  up  or  flattened 
against  the  plate,  Avhile  the  same  projectile  fired  at  a higher 
A’elocity  may  go  through  the  same  plate  almost  uninjimed.  On 
this  principle  a lead  shot  may  be  fired  through  an  iron  plate,  or 
a tallow  candle  through  a pine  board. 


PEOJECTILES. 


315 


861.  For  the  larger  calibre  of  rifled  guns,  but  one  style  of 
armor-pnncbing  projectile  is  usually  suppbed ; this  being  a 
shell  with  thick  walls,  which  may  be  fired  empty  as  a shot,  or 
with  the  biu’sting-charge  to  give  tlie  explosive  action  of  a shell. 
It  is  found  to  penetrate  best  when  fired  as  a shot ; the  action 
of  the  bursting-charge,  generally  taking  place  before  the  pro- 
jectile reaches  its  full  depth,  interferes  with  penetration  when 
the  armor  is  very  strong ; but  when  the  front-plates  are  not 
very  thick,  the  backing  may  be  shattered  to  a greater  extent 
from  the  explosion  of  a bursting-charge. 

865.  ADTANTxiGES  OF  - StEEL  OVER  ClIILLED  PROJECTILES. 
— Late  trials  have  sho'wn  a superiority  of  steel  projectiles  over 
those  made  of  chilled  cast-iron,  and  although  the  former  are 
somewhat  more  expensive  than  the  latter,  on  the  principle  that 
the  best  is  at  the  same  time  the  cheapest,  it  would  be  misplaced 
economy  to  leave  any  means  imavailed  of  to  increase  the 
penetrating  power  of  projectiles. 

The  quality  of  chilled  projectiles,  from  the  nature  of  their 
manufacture  (Art.  809),  is  necessarily  unreliable  ; whereas  this 
is  not  the  case  with  hammered  cast-steel,  or  at  least  not  to  the 
same  extent  by  far,  even  w'hen  large  masses  are  produced,  and 
the  difliculty  of  manufacture  increases  with  the  calibre. 

The  most  essential  difl:erence  in  the  behavior  of  steel  and 
chilled  projectiles  on  striking  the  target,  consists  in  the  reaction 
on  the  ]irojectile  showing  itself  in  the  latter  by  breaking  up, 
while  the  former  are  only  set  up.  As  the  breaking  up  of  the 
chilled  shells  may  take  place  before  the  bursting-charge  comes 
into  operation,  whereby  the  rending  effect  is  considei’ably  prej- 
udiced, this  material  appears  far  less  adapted  for  shells  than 
steel. 

The  superiority  of  steel  in  this  respect  is  still  further  in- 
creased by  the  fact  that  the  steel  shell,  can  have  thinner  walls, 
consequently  a larger  chamber,  and  can  thus  hold  a larger 
bursting-charge  than  the  chilled  metal. 

866.  EXPEPJMENTS  AGAINST  AEMOP.— The  ex- 
periments made  of  late  years,  although  numerous  and  costly, 
have  not  been  carried  out  in  such  a manner  as  to  afford  the 
necessary  data  for  establishing  the  laws  of  penetration.  In 
these  ex'periments  numerous  circumstances  have  been  approx- 
imated to,  or  assumed,  and  there  have  been  generally  many 
points  of  absolute  difference  between  the  experimental  struc- 
tures and  those  to  be  built  for  service. 

By  far  the  larger  number  of  all  the  experiments  of  which 
we  have  record,  were  made  upon  targets  small  in  area,  al- 
though representing  the  entire  thickness  of  parts  to  be  used  in 


316 


NAVAL  ORDNANCE  AND  GUNNERY. 


practice  ; these  small  targets  being  held  and  braced  up  in  var- 
ious ways,  generally  different  from  the  manner  in  which  the 
same  targets  would  be  supported  were  they  to  fonn  integral 
parts  of  a permanent  structure.  ISTor  have  the  tests  applied  to 
these  targets  been  as  a rule  correct  imitations  of  what  they 
would  probably  receive  in  seiwice;  having  been  fired  at  delib- 
erately with  the  guns  and  projectiles  of  the  same  countrj^,  as 
the  targets. 

867.  Aemor-Plates  and  Backing. — The  following  deduc- 
tions have  been  made  from  trials  with  armor-plates  extending 
over  several  years. 

The  best  material  to  resist  projectiles  is  soft,  tough  wrought- 
iron  ; and  to  attain  these  qualities  it  should  be  pure,  free  from 
sulphur,  phosphorus,  and  carbon.  Steely-iron,  commonly 
known  as  homogeneous  iron,  puddled  steel,  etc.,  when  in  large 
masses  is  easily  cracked  by  projectiles,  and  is  not,  therefore, 
suitable  for  armor-plates.  Soft-steel  may  be  used  for  armor- 
plates  ; but  when  cost  is  taken  into  consideration,  it  is  doubtful 
if  it  possesses  any  advantages  over  wrought-iron. 

Boiled  iron  does  not  offer  quite  so  much  resistance  as  ham- 
mered iron,  3’et  if  the  size  of  the  plate  admit  of  it,  it  is  to  be 
preferred  on  the  score  of  economy.  Plates  should  be  as  large 
as  possible  to  reduce  the  number  of  joints  which  are  lines  of 
weakness. 

A solid  plate  offers  for  the  same  thickness  a greater  resist- 
ance to  a projectile  than  a laminated  one,  or  one  made  up  of 
several  thinner  plates ; but  when  the  surface  is  rounded  in 
shape,  and  of  small  extent,  as  in  the  Monitor  turrets,  the  latter 
may  be  used  to  great  advantage,  as  great  thickness  may  thereby 
be  easil}^  obtained. 

It  is  difficult  in  practice  to  obtain  very  large  and  thick 
masses  in  great  numbers  of  uniformly  good  quality  and  at  a 
moderate  cost. 

With  targets  made  up  of  several  plates,  the  chief  difficulty 
has  been  to  contrive  bolts  of  suitable  form,  and  to  dispose  them 
so  that  the  strength  of  fhe  target  is  not  quickly  impaired  by 
the  shearing  of  the  bolts  from  the  vibrations  of  the  separate 
plates,  or  by  their  fracture  on  being  struck  by  projectiles. 

868.  Wood-backing  alone,  unless  combined  with  rigid  hori- 
zontal angle  iron  stringers,  affords  but  little  support  to  the 
plate ; that  is  to  say,  a projectile  which  is  capable  of  penetrating 
a plate  unbacked,  v/ill  also  be  capable  of  doing  so  if  it  be 
backed  with  wood  alone.  Wood-backing  is,  however,  of  great 
value  because  it  distributes  the  blow  ; it  deadens  the  vibrations 
and  saves  the  fastenings ; also  it  stops  the  splinters. 


PROJECTILES. 


317 


The  best  form  of  backing  appears  to  be  that  in  which  wood 
is  combined  with  strong  horizontal  angle-iron  attached  to  the 
inner  skin,  and  extending  to  the  armor-plates  ; this,  by  giving 
rigidity,  very  considerably  assists  the  plate  to  resist  penetra- 
tion. 

An  inner  skin  of  iron  is  of  the  greatest  possible  advantage  ; 
it  renders  the  backing  more  compact,  and  prevents  the  passage 
of  many  splinters. 

Oak  and  teak  are  the  most  suitable  timbers  for  backing- 
plates,  and  are  used  as  such  on  vessels.  A yielding  backing  is 
found  to  occasion  less  strain  on  the  fastenings  than  a very  hard 
one. 

Where  projectiles  are  made  of  the  same  material,  and  are 
similar  in  shape,  their  penetration  into  unbacked  plates  is  nearly 
in  proportion  to  their  living  force,  or  their  weight  multigylied 
ly  the  squares  of  the  velocity  of  impact. 

869.  The  resistance  which  an  unbacked  plate  offers  to  pen- 
etration is  nearly  in  proportion  to  the  square  of  its  thickness, 
provided  this  thickness  be  confined  within  ordinary  limits.  In 
the  case  of  oblique  plates  the  penetration  diminishes  nearly 
with  the  sine  of  the  angle  of  incidence. 

870.  The  most  suitable  material  for  shells  to  be  used  against 
iron  plates  is  tempered  steel.  These  projectiles  should  be  made 
of  cylindrical  shape,  with  thick  sides  and  bottom  to  direct  the 
explosive  effect  of  the  charge  forward  after  penetration  is  ef- 
fected. 

The  most  suitable  material  for  solid  shot  is  hard,  tough 
cast-iron. 

Palliser’s  chilled  shot  are  made  of  this  material,  and  so  are 
the  shot  made  for  our  service. 

871.  It  follows  from  the  preceding,  that  the  most  suitable 
covering  or  shield  for  cannon  is  a conical-shaped  turret  made 
of  Avrought-iron  plates,  as  large  as  it  is  practicable  to  make 
them,  backed  Avith  oak  or  teak. 

To  pi’otect  the  men  from  the  fragments  of  projectiles  Avhich 
may  penetrate  completely  through  this  covering,  there  should 
be  an  “inner  skin”  of  thick  boiler-plate  placed  behind  the 
wood. 

872.  With  our  XY-inch  cast-iron  projectiles,  made  of  the 
best  charcoal-iron,  poured  and  worked  in  a peculiar  manner  so 
as  to  obtain  hard  and  solid  masses,  the  penetration  is  quite  as 
great  and  uniform  as  that  obtained  with  steel  shot  of  equal 
Aveights  propelled  by  similar  charges,  the  only  difference  being 
that  the  ii’on  breaks  after  passing  through,  Avhile  the  steel  is 
only  compressed  or  flattened,  a result  rather  in  favor  of  the  iron 


318 


NAVAL  ORDNANCE  AND  GUNNERY. 


shot,  if  entrance  is  made  between-decks,  where  men  are  exposed 
to  its  fragments. 

873.  Effects  on  Wood. — The  effect  of  a projectile  fired 
against  wood  varies  with  the  nature  of  the  wood  and  the  direction 
of  the  penetration.  If  the  projectile  strike  perpendicular  to  the 
fibres,  and  the  fibres  be  tough  and  elastic,  as  in  the  case  of  oak, 
a portion  of  them  are  crushed,  and  others  are  bent  under  the 
pressure  of  the  projectile,  but  regain  their  form  as  soon  as  it 
has  passed  by  them. 

It  is  found  that  a hole  formed  in  oak  by  a hall  of  four 
inches  in  diameter  closes  up  again,  so  as  to  leave  an  opening 
scarcely  large  enough  to  measure  the  depth  of  the  penetration. 

The  size  of  the  hole  and  the  shattering  effect  increases  rap- 
idly for  the  large  calibres.  A nine-inch  projectile  has  been 
found  to  leave  a hole  that  does  not  close  up,  and  to  tear  away 
large  fragments  from  the  back  portion  of  an  oak  target  repre- 
senting the  side  of  a ship-of-war,  the  effect  of  which  on  a vessel 
would  have  been  to  injure  the  crew  stationed  around ; or,  if 
the  hole  had  been  situated  at  or  below  the  water-line,  to  have 
endangered  the  vessel.  If  penetration  take  place  in  the  direc- 
tion of  the  fibres,  the  piece  is  almost  always  split,  even  by  the 
smallest  shot,  and  splinters  are  thrown  to  a considerable  dis- 
tance. 

In  consequence  of  the  softness  of  white-pine,  nearly  all  the 
fibres  struck  are  broken,  and  the  orifice  is  nearly  the  size  of  the 
projectile ; for  the  same  reason  the  effects  of  the  projectile  do 
not  extend  much  beyond  the  orifice. 

When  a round-shot  strikes  against  a surface  of  oak,  as  the 
side  of  a ship,  it  will  not  stick  if  the  angle  of  incidence  he  less 
than  15°,  and  if  it  do  not  penetrate  to  a depth  nearly  equal  to 
its  diameter. 

874.  Effect  on  Eaktii. — Earth  possesses  advantages  over 
all  other  materials  as  a covering  against  projectiles ; it  is  cheap 
and  easily  obtained,  it  offers  considerable  resistance  to  penetra- 
tion, and  to  a certain  extent  regains  its  position  after  displace- 
ment. It  is  found  by  experience  that  a projectile  has  very  lit- 
tle effect  on  an  earthen  parapet  unless  it  passes  completely 
through  it,  and  that  injury  done  by  day  ca'n  he  promj)tly 
repaired  by  night. 

The  powers  of  resistance  of  pure,  compact  quartz-sand  to 
the  penetration  of  projectiles  has  been  found  very  much  to  ex- 
ceed that  of  ordinary  earth. 

The  size  of  the  openings  formed  by  the  passage  of  a pro- 
jectile into  earth  is  about  one-third  larger  than  the  projectile, 
increasing,  however,  toward  the  outer  orifice. 


PEOJECTILES. 


319 


Elongated  projectiles  are  easily  deflected  from  their  course 
in  earth.  They  are  sometimes  found  lying  in  a position  at 
right-angles  to  their  course,  and  sometimes  Avith  the  base  to  the 
front. 

Unless  a shell  be  very  large  in  proportion  to  the  mass  of  earth 
penetrated,  its  explosion  Avili  produce  but  little  displacement. 

875.  Effect  on  Masonka’. — The  effect  of  a projectile 
against  masonry  is  to  form  a truncated  conical  hole  terminated 
by  another  of  a cylindrical  form.  The  material  in  front  of 
and  around  the  projectile  is  broken  and  shattered,  and  the  end 
of  the  cylindrical  hole  even  reduced  to  poAV'der. 

Pieces  of  the  masonry  are  sometimes  thrown  50  or  60  yards 
from  the  Avail. 

The  elasticity  developed  by  the  shock  reacts  upon  the  pro- 
jectile, sometimes  throwing  it  back  150  yards. 

The  exterior  opening  varies  from  four  to  fix'e  times  the 
diameter  of  the  projectile,  and  the  depth  varies  Avith  the  size 
and  density  of  the  projectile  and  its  velocity. 

Solid  cast-iron  shot  break  against  gmnite,  but  not  against 
freestone  or  brick.  Spherical  shells  are  broken  into  small 
fragments  against  each  of  these  materials. 

The  most  destructive  projectile  against  masonry  is  the  elon- 
gated percussion  shell. 

876.  PuNGiiiNG  AND  PACKING. — It  lias  been  shoAim  that  the 

penetration  of  a projectile  depends  more  upon  velocity  than 
weight,  and  that  the  elongated  is  a better  form  than  the 
spherical  for  mere  penetration  ox  ]?uncliing.  It  must,  hoAvever, 
be  remembered  that  A’ery  heavy  shot,  tired  with  A^elocities 
which  might  not  enable  them  to  penetrate  or  punch  holes  in 
iron  armor,  may  still  do  great  damage,  especially  if  many  ai'e 
fired  successively,  by  breaking  bolts  and  shaking  the  whole 
fabric ; also,  that  a spherical  shot,  having  a larger  diameter 
than  an  elongated  projectile,  may  often  do  more  damage  in 
cracking  or  shattering  a plate,  than  the  latter  in  punching  it, 
the  work  done  by  the  ball  being  distributed  over  a larger  area ; 
the  same  argument  Avill  apply  to  the  case  of  tivo  elongated  pro- 
jectiles, having  different  diameters,  striking  a target  Avith  the 
same  force,  as  measured  by  Hence  there  are  two  general 

methods  of  attempting  the  destruction  of  iron-clad  vessels, 
termed  respectively  racking  and  punching.  We  have  pre- 
ferred the  racking  system. 

877.  The  Racking  System  requires  heavy  projectiles  of 
large  diameters,  fired  Avith  Ioav  velocities,  to  destroy  and  shake 
off  the  armor  by  repeated  shocks  Avithout  penetration,  and  thus 
to  expose  the  vessel  to  the  effects  of  ordinary  projectiles. 


320 


NAVAL  OEDNANCE  AND  GUNNEEY. 


878.  The  Punching  System  requires  elongated  projectiles 
of  moderate  weight,  fired  with  high  velocities,  so  as  to  perforate 
the  armor,  and,  if  near  the  water-line,  to  sink  the  vessel,  or  at 
any  part  to  injure  men  or  machinery,  or  explode  the  magazine 
within  the  vessel. 

879.  The  Two  Systems  ComMned. — The  two  forces  may 
prepare  the  way  for  each  other,  so  as  to  produce  a more  for- 
midable result  than  when  they  are  independently  exercised. 

The  defect  of  the  light-shot  system  when  the  range  is  very 
long  or  the  armor  very  thick,  and  of  the  heavy-shot  system 
when  the  range  is  even  very  short  and  the  armor  is  laminated 
or  so  constructed  as  to  suffer  little  from  racking  and  shaking, 
is  the  waste  of  power  in  producing  local  effect,  that  is  fmitless 
because  it  is  incomplete. 

By  combining  the  two  systems,  the  light  fast  shot  may 
weaken  the  armor  by  the  loss  of  substance  and  continuity, 
until  the  heavy  shot  can  carry  in  a large  section  of  it  bodily ; 
and  at  the  same  time  the  general  straining  and  cracking  of 
plates  produced  by  the  heavy  shot  will  make  punching  all  the 
easier. 

880.  Force  of  Impact. — In  order  to  estimate  the  probable 
effect  of  a projectile  upon  an  object,  it  is  necessary  to  calculate 
the  total  energy  in  the  projectile  at  the  moment  of  impact. 

The  “ms  viva,^'  or  total  energy  of  a body  in  motion,  is  the 
whole  mechanical  effect  or  work  which  it  will  produce  on  being 
brought  to  a state  of  rest,  without  regard  to  the  time  occupied ; 
and  it  varies  as  the  weight  of  the  body  multiplied  by  the  square 
of  its  velocity.  This  work,  accumulated  in  the  moving  body, 
is  represented  by  the  weight  which  it  is  capable  of  raising  one 
foot  high,  and  is  equal  to  the  weight  in  pounds  of  the  moving 
body  multiplied  by  the  square  of  its  velocity  in  feet,  and 
divided  by  twice  the  accelerating  force  of  gravity. 


Or,  Total  Energy 


wv^ 

- V 


where  w =■  weight  of  projectile, 

V = final  velocity, 
g = force  of  gravity.  (32.2  ft.) 

Example. — Thus,  if  a projectile  of  165  lbs.  weight  be  mov- 
ing with  a velocity  of  1170  feet  per  second,  the  work  accumu- 
lated in  it,  or  the  power  it  will  actually  exert  on  impact,  is 

165  X (1170)’ 


PROJECTILES. 


321 


881.  The  Punching  Effects  of  Pkojectiles  are  iisuallj 
compared  by  calculating  wbat  is  termed  the  energy  ])er  inch  of 
circumference  in  foot-tons,  which  is  found  by  dividing  the 
total  energy  by  the  number  of  inches  in  the  circumference  of 
the  projectile. 

Enero-y  per  inch  of  circum.  = - . — ^ — 7-,, 

^ 2y  X 27t  K’ 

where  R = radius  of  projectile. 

It  will  be  readily  seen  that  more  force  is  required  to  drive 
a large  projectile  through  a plate  than  a small  one. 

Therefore,  if  the  object  is  to  know  the  depth  to  which  pro- 
jectiles will  penetrate,  size  must  enter  as  an  element  in  the 
question.  It  has  been  found  that  an  approximate  standard  of 
comparison  is  furnished  by  dividing  the  total  energj^  stored  up 
in  a projectile  by  its  circumference. 

Tlie  reason  of  this  is  plain.  Suppose  the  projectile  to  act 
literally  as  a punch,  and  to  clip  a round  disk  out  of  the  plate  of 
sufficient  size  to  allow  it  to  enter ; it  is  clear,  in  such  a case, 
that  the  work  performed  is  simply  that  of  shearing  the  plate 
round  the  edge  of  the  projectile.  Thus  the  energy  of  the  pro- 
jectile will  be  met  b}’  the  resistance  required  to  shear  the  tar- 
get in  this  manner,  in  a line  which  coincides  with  the  exact 
circumference  of  the  projectile.  Ro  doubt  this  supposition  is 
not  correct,  as  any  one  knows  who  has  seen  plate-liring.  It  is, 
however,  sufficiently  near  the  truth  to  furnish  a standard  of 
comparison  between  projectiles  of  various  calibres. 

21 


CHAPTER  YII. 


GUN-CAEEIAGES.* 

Section  I — United  States  Na/oal-gun-carriages. 

882.  Geneeal  Consideeations. — The  first  of  all  consider- 
ations as  to  the  mounting  of  the  battery,  is  that  it  should  admit 
of  the  utmost  possible  rapidity  of  fire,  united  with  accuracy  of 
aim.  It  is  important  to  secure  the  greatest  possible  efficiency 
of  the  weapon  under  the  conditions  in  which  it  is  required  to 
be  employed. 

The  daty  of  providing  the  most  perfect  means  of  working 
guns  seems  to  be  second  only  in  importance  to  that  of  adopting 
the  best  material,  form,  and  construction  for  the  gun  itself.  Of 
two  shnilar  guns,  that  which  can  tire  the  greatest  number  of 
rounds  in  a given  time  is  certainly  most  efliective,  and  rapidity 
of  fire  depends  much  more  on  the  gun-carriage  and  conveniences 
for  loading,  than  upon  any  peculiarity  attaching  only  to  the  gun. 

883.  Owing  to  the  increase  in  the  size  and  power  of  ordnance 
since  the  introduction  of  armor,  gun-carriages  have  gradually  be- 
come elaborate  machines;  and  mechanical  science,  in  the  hands 
of  naval  experts,  has  produced  carriages  and  slides  which  enable 
the  heaviest  guns  to  be  easily,  accurately,  and  safely  worked  on 
the  broadsides  of  ships.  The  great  superiority  of  wrought-iron 
to  timber  as  a material  for  gTin-carriages  is  now  universally  ac- 
knowledged. 

881.  Although  the  mechanism  has  been  greatly  improved, 
the  physical  force  of  the  gun’s  crew  is  still  the  source  of  the 
power  by  which  the  gun  is  worked.  As  long  as  this  is  the  ease 
a practical  limit  to  the  weight  of  glin  that  can  be  efficiently 
worked  is  imposed,  and  it  would  seem  that  this  limit  has  been 
already  reached.  As  still  larger  guns  are  in  prospect,  the 
necessity  naturally  presents  itself  for  substituting  an  inanimate 
and  unlimited  power — like  that  of  steam  acting  directly  or 
through  the  medium  of  Avater  under  pressure. 

885.  The  heat  and  elasticity  of  steam,  and  the  difficulty  of 
conveying  it  from  place  to  place,  render  it  unsuitable  for  direct 
apjjlieation  to  the  AArnrhing  of  guns  ; but  in  the  hydraulic  system, 
so  successfully  developed  for  commercial  purposes,  steam  is 

* Compiled  by  Lieut.  Commander  G.  W.  Coffin,  TJ.  S.  Navy. 


GUX-CARRIAGES. 


323 


made  available  as  a central  source  of  power,  by  employing  a 
steam-eaglns  to  pump  crater  into  pipes,  wliicb  transmit  it  at 
bigli  pressure  to  the  various  points  of  application  of  the  force 
where  it  acts  in  hydraulic  pressure  to  produce  the  different 
movements  required.  It  is  this  system  which  has  been  applied 
to  the  loading  and  working  of  heavy  guns. 

886.  The  application  of  this  system  to  naval  guunery  was 
put  in  successful  practice  in  some  of  our  iron-clads  during  the 
late  war. 

Loading  from  below  deck  by  depressing  the  muzzle  (Art. 
1028)  was  devised  by  Mr.  Stevens  and  practised  on  board  one  of 
our  vessels. 

Taking  up  the  recoil  on  a steam  or  air  cylinder  (Art.  102G), 
and  running  out  and  in  by  steam  as  recommended  by  Captain 
Eads,  was  also  successfully  practised. 

Muzzle-pivoting  the  guns  so  as  to  obtain  25  deg.  elevation 
and  lateral  train  in  a fixed  turret  with  a port  no  larger  than 
the  muzzle  was  practised  on  some  of  our  monitors  with  entire 
success. 

887.  Requirements  of  Mechanical  Carphages. — These 
arp  : powerful  moving-machinery  so  contrived  as  to  be  unaffected 
by  the  concussion  of  firing;  self-acting  controlling  gear,  almost 
independent  of  human  carelessness ; the  gradual  absorption  of, 
rather  than  ridgid  re.-istance  to,  shocks ; Lie  dispersion  of  con- 
cussious  over  large  surfaces  ; independence  of  distortion  of,  or 
other  injuries  to,  the  ship’s  side  ; smoothness  and  ease  of  motion 
in  every  direction,  and  safety  under  all  conditions  of  the  sea. 

888.  Disappearing  Systems. — Guns  mounted  on  the  disap- 
pearing principle,  are  arranged  to  drop  when  fired  into  a position 
in  which  they  can  be  loaded  under  cover,  and  from  which  they 
are  only  raised  when  required  again  to  deliver  their  fire.  (Art. 
1022.) 

It  is  yet  undecided  how  far  this  principle  is  generally  appli- 
cable in  substitution  of  turrets  for  the  protection  of  guns  at  sea. 
One  great  difficulty  would  seem  to  be  that  of  effectually  closing 
the  opening,  by  which  the  gun  must  pass  up  and  down,  through 
the  deck  so  as  to  prevent  the  entry  of  water,  and  it  is  difficult 
to  conceive  how  rapidity  or  accuracy  of  fire  can  be  attained  in 
this  way. 

889.  In  this  system  the  gun  must  not  only  be  loaded  while 
lowered  and  under  cover,  but  it  is  usually  fitted  to  be  trained 
and  aimed  while  there,  by  indirect  methods,  such  as  by  teles- 
copic apparatus  adapted  to  the  gun’s  axis,  and  so  arranged  that 
it  can  enable  an  observer  to  look  over  and  above  the  cover.  It 
is  not  probable  that  any  such  indirect  instrumental  apparatus 


324 


NAVAL  OEDNANCE  AND  GUNNEEY. 


can  be  constracted  which,  when  adapted  to  a heavy  rifled  gun 
shall  admit  of  the  accuracy  of  fire  of  the  piece  being  adequately 
met  by  a corresponding  exactness  of  aim. 

The  disappearing  principle  was  first  recommended  by  Cap- 
tain J.  B.  Eads,  and  was  adopted  for  trial  in  several  of  our 
western  iron-clads. 

890.  The  MAKsmuy  Beoahside  Caeeiage  (W ood). 

Nomenclature. 


A.  — Brackets. 

B.  — Bear  Transom. 

C.  — Breast  Piece. 

D.  — Sweep  Piece. 

I. — Saucer. 

F. — Front  Transom 

L. — Boss  of  EoUer  Handspike. 


M.  — ^Trucks. 

N.  — Cap  Squares. 

9. — Side  Tackle-bolt. 

10.  — Train  “ “ 

11.  — Transporting  Tackle-bolt. 
K. — EoUer  Handspike. 

P. — Washer  and  pin. 


Dimensions. 


Height  of  Trunnions 

Extreme  length  of  Caniage 

Width  of  Front 

Width  of  Eear 

Thickness  of  Wood 


34  inches. 
68 

39.5  “ 

44 

7 r.  “ 


891.  The  Braclcets,  A,  are  made  of  heavy  white  oak, 
jogged  and  dowelled  together  as  in  Figure  208,  and  firmly 
secured  to  each  other  by  the  bolts  1,  2,  3,  4,  5 — 1 and  2 cap- 
stpiare  bolts;  3,  4,  and  6,  bracket  bolts.  The  rear  portion  of 
the  brackets  are  extended  dotvnward  to  the  deck,  the  upper 
descending  by  a curve  and  two  steps ; the  latter  being  faced 
by  strips  of  metal,  to  take  the  chafe  of  the  handspikes  when 
used  on  them.  The  brackets  are  joined  by  the  Front  (F)  and 
Rear  Transoms  (B),  which  are  jogged  into  them,  the  front 
transom  having  two  bolts  (7  and  8),  and  the  rear,  one  (6) ; the 
Front  Transom,  F,  is  scored  out  to  permit  vertical  motion  of 
the  chase  of  the  gun  in  the  carriage. 

892.  The  Breast  Piece,  C,  is  firmly  bolted  to  the  front 
transom  and  works  against  the  Sweep  Piece,  D,  fitted  to  ship 
and  nnship  from  the  ship’s  side  by  composition  pins  and 
sockets. 

893.  The  Socket  Plate  consists  of  a metal  plate,  with  in- 
dentations or  sockets  for  the  boss,  F,  of  the  Roller  Handspike, 
K,  to  take  in.  It  is  placed  under  and  at  the  rear  edge  of  the 
Transom  B. 

894.  The  Roller  Handspike,  K,  consists  of  a bronze  head 


GUi!f-CAERIAGES. 


325 


and  socket  with  a hickory  handle ; in  the  head  are  placed  two 
lujnum-vitm  rollers,  four  inches  in  diameter,  working  on  a line 
through  the  sides  of  the  head.  A boss,  L,  is  cast  at  the  junc- 


ISll 

iLEPji  41 

|I';I 

■,ILJ 

ll':| 

kM 

IB  ff  '': 

° i' 

1>W 
rill  K 

r"'  ‘1 

M 

<5001-  ^ socket,  making  an  angle  of  70°  with  the 

socket  is  placed  the  hickory  handle, 
hen  in  use,  the  lift  of  the  carriage  is  greatest  with  thp 
OSS,  L,- vertical,  as  it  is  then  raised  i inch  above  the  deck.  In 


326 


NAVAL  ORDNANCE  AND  GUA^NERT. 


service  the  best  result  is  obtained  with  the  handle  at  the  hip  ; 
care  must  be  used  to  maintain  the  axis  of  the  roller  perpendicu- 
lar to  the  motion  of  the  carriage,  otherwise  the  weight  cants 
the  head,  causing  the  rollers  to  deface  the  deck. 

895.  The  Truch  Axle  is  let  into  the  Brackets,  A,  and 
secured  to  them  by  the  cap-square  bolts,  1,  and  the  brace,  12, 
through  which  the  other  cap-square  bolt  passes  and  is  set  up 
by  a nut. 

896.  The  Tr^iclcs,  M,  are  of  lignum^itoe,  one  calibre  in 
thickness,  and  retained  on  the  axle  Ijy  a washer  and  flange- 
pin,  P. 

897.  The  Saiccer,  I,  is  of  composition,  and  secured  to  the 
Rear  Transom,  B.  From  its  shape  it  permits  a horizontal 
movement  of  the  lower  end  of  the  screw,  due  to  its  deviation 
from  the  perpendicular,  in  elevation  or  depression. 

898.  Resistance  to  Recoil. — As  the  recoil  of  the  gun  is  to 
the  rear  and  downward,  considerable  resistance  is  offered  by 
the  friction  excited  between  the  carriage  brackets  and  deck ; 
the  recoil  is  thus  checked  in  proportion  to  the 'friction  exerted. 

899.  Manoeuvring  the  Carriage. — To  run  the  carriage  in 
and  out,  or  transport  it  about  the  deck,  the  Roller  Handspike, 
K (Fig.  208),  is  shipped  under  the  rear  transom,  B,and  the  gun 
readily  moved  on  its  trucks  and  the  roller  handspike. 

900.  Elevation  Chtainahle. — Broadside  carriages  are  so  con- 
structed as  to  give  11°  elevation  and  7°  depression  to  the  gun, 
and  for  four  different  heights  of  the  lower  port-sill  above  the 
deck,  viz.,  24,  20,  18,  and  16  inches,  according  to  the  require- 
ments of  their  position. 

901.  Preservation. — Hew  carriages  should  be  kept  well 
painted,  and  the  trucks,  axle-trees,  and  trunnion-holes  oiled. 
Staining  or  keeping  them  bright  is  strictly  prohibited. 

902.  Gun  Tacldes  are  to  be  of  well-stretched  manilla,  cut 
of  suflicient  length  to  allow'  of  full  recoil,  and  with  end  enough 
to  hitch  around  the  straps  of  their  inner  blocks. 

903.  Metallic  Gun  Taclde  Blocks  are  supplied  to  all  Har- 
shly and  heavy  pivot  carriages;  these  have  ribs  on  the  hooks, 
which  keep  the  blocks  fair  with  the  falls,  and  prevent  their 
fouling  on  recoil. 

Breechings  are  of  the  best  three-strand,  shroud-laid,  and 
soft,  hemp  rope,  9 and  10  inch  for  the  larger  guns,  from  6 to 
9 for  the  smaller;  they  should  be  long  enough,  when  fitted,  to 
allow  the  muzzle  of  the  gun  to  come  one  foot  inside  of  the 
port.  Breechings  are  never  to  be  covered,  blackened,  or  in 
any  way  rendered  less  pliable  than  when  first  fitted. 

904.  Wkodght  ieon  Caekiage  fok  VIIITnch  Gun. 


GTIN-CAEIIIAGES. 


327 


Fig.  209. 


328 


NAVAL  ORDNANCE  AND  GUNNERY. 


Nom.endature. 


A.  — Brackets. 

B.  — Rear  Transom. 

C.  — Breast  Piece. 

D.  — Sweep  Piece. 

P. — Front  Transom. 

K.  — Composition  Shoes. 

L. — Elevating  Screw. 


M.  — Trucks. 

N.  — Cap  Squares. 

O.  — Angle  Iron. 

9. — Side  Tackle-bolt. 

10. — Train  “ 

11 .  — Transporting-bolt. 


Principal  Dimensions. 


Height  of  Trunnion 36  inches. 

Extreme  Length  of  Carriage 56  ‘‘ 

Width  of  Carriage 27  “ 

Thickness  of  Iron f “ 

Weight  of  Carriage 981  lbs. 


905.  The  Brackets,  A,  are  made  of  f inch  Tvronglit-iron  ; on 
tlieir  rear  lower  portion  are  placed  composition  shoes,  K, 
which  rest  npon  the  depk. 

906.  The  Transoms,  BF,  of  the  iron  carnage,  are  of 
wronght-iron  plate,  and  occupy  the  same  position  as  in  the 
wooden  carriage  ; the  front  transom,  F,  and  rear,  B,  are  riveted 
to  the  brackets  by  angle-iron,  O. 

907.  The  Truck  iVxle  passes  throngh  the  forward  lower 
ends  of  the  brackets,  shown  in  the  figure  by  the  dotted  line; 
on  these  axles  composition  trucks,  M,  one  calibre  in  thickness, 
are  placed. 

908.  Blevating  Gear. — At  the  height  of  the  Breast  Piece,  D, 
and  just  in  rear  of  the  Trunnion  Holes,  are  rods  connecting  the 
brackets;  on  these  are  pivoted  a bar,  P,  whose  rear  end  rests  on 
the  head  of  the  male  and  female  screw,  L,  which  works  in  the 
bed-plate  of  the  carriage  to  such  an  extent  that  when  the  gnn 
has  extreme  elevation,  the  screw  is  considerably  below  the 
Bed-plate,  B,  yet  does  not  touch  the  deck. 

909.  Side  (9),  Train-tackle  (10),  and  Transporting  Bolts 
(11)  are  of  composition,  and  occupy  the  same  position  as  in  the 
wood  carriage. 

910.  The  Breast  Piece,  C,  is  of  wood  and  arranged  to  be 
at  the  height  of,  and  work  on,  the  Sweep  Piece,  D. 

The  Socket  Plate  is  very  similar  to  that  on  the  wood  car- 
riage, occupying  the  same  position. 

911.  Cap  Sguares,  N,  are  of  composition,  and  secured  to 
the  brackets  by  screw  nuts. 

912.  The  Recoil  is  checked  by  the  friction  exerted  between 
the  deck  and  the  composition  shoes,  K,  whose  rear  edges  are 
curved  upward  to  prevent  injury  to  the  deck  on  recoil. 


GUX-CAERIAGES. 


329 


913.  Wroiiglit-iron  is  employed  in  the  mannfactnre  of  gun- 
carriages  for  the  reason  tliat  it  does  not  splinter  like  cast-iron 
on  the  impact  of  shot.  Because  of  their  less  weight,  less  space 
occupied,  and  iron-liability  to  injury  in  service,  these  carriages 
promise  to  entirely  supersede  the  wood  carriages. 

914.  When  Parrott  guns  are  mounted  in  broadside,  a Mar- 
silly  carriage  is  employed,  differing  from  the  ordinary  carriages 
in  that  the  brackets  are  extended  farther  to  the  rear  to  accom- 
modate the  additional  length  of  gun. 

915.  Pitot  Cakeiages. — Object. — Guns  whicli  are  expected 
to  be  fired  at  greater  elevations  than  the  ordinary  port  will 
admit  of,  are  mounted  upon  pivot-carriages,  which  give  an 
elevation  of  20°  to  the  gun,  and  a much  larger  arc  of  train 
than  the  broadside  carriage,  the  bulwarks  of  the  ship  being 
arranged  to  let  down  in  order  to  accomplish  it. 

On  Spar  Declcs  the  slide  may  usually  be  pivoted  amidships, 
and  on  both  bows  when  placed  forward ; if  aft,  astern  and  on 
both  quarters ; and  there  being  fewer  obstructions  aft,  the  gun 
in  some  cases  has  a full  sweep  from  one  beam  to  the  other. 

On  Gun  Declcs  the  arc  of  train  is  somewhat  limited,  yet  con- 
siderably greater  than  with  the  broadside  carriage ; tlie  ship’s 
side  is  arranged  to  let  down  like  the  bulwarks  on  spar-decks, 
the  fighting  pivot  being  at  the  ship’s  side. 

916.  The  XI-Inch  Pivot  Caekiage  (Wood)  is  composed  of 
two  principal  parts,  the  slide  and  the  carriage  proper  (Fig  210),  the 
former  being  secured  at  one  of  its  ends  by  a pivot  bolt,  P. 
Fig.  212  is  traversed  by  tackles,  to  bring  the  guns  to  bear  upon 
the  object,  or  to  change  position  in  firing. 

917.  The  Carriage  differs  from  the  Broadside  in  the  suppres- 
sion of  trucks,  and  the  substitution,  therefor,  of  three  transoms 
B (Fig.  214),  front,  middle,  and  rear ; the  lower  sides  of  which 
rest  upon  the  slide,  and  by  their  friction  modify  the  recoil. 

918.  The  Brackets.^  A,  are  in  two  parts,  gogged  and  dowelled 
together,  and  they  and  the  transoms,  B,  are  firmly  secured  to 
each  other  by  the  bolts,  O. 

919.  The  Transoms.,  B,  extend  beyond  the  brackets  and 
slide-rails,  C,  the  forward  being  for  the  compressors,  f,  and  the 
rear  for  the  double  eye  bolted  to  it,  to  which  the  blocks  of  the  in 
and  out  tackles  hook ; a third  called  the  Breast  Transom  J is 
bolted  between  the  front  ends  of  the  brackets,  and  is  scored  out 
as  in  the  Broadside  carriage. 

920.  The  Journal  Plates  (g)  attached  to  the  brackets,  carry 
rollers  on  an  eccentric  axle,  extending  across,  between,  and 
beyond  the  brackets;  levers  are  supplied  to  be  shipped  on 


330 


NAVAL  ORDNANCE  AND  GUNNERY. 


(L 

O 

H 


WOODEN  PAKT9. 

N.  Battens  and  Slats. 

Y.  Preventer  Breechings 


METAL  PARTS. 

Z.  Upper  Pivot-plate. 

1.  IMiddle  Boiler-plate. 

2.  Eyes  for  Tackles. 

8.  Harter  Straps. 

4.  Rail-plates. 


Fig.  210. — Plan  of  Xl-Inch  Gun-carriage  and  Slide. 


BOTTOM  VIEW. 


GUJSr-CAERIAGES, 


331 


tlie  end  of  the  axles,  throwing  the  eccentrics  in  and  out  of 
action. 


Fig.  211— Plan  of  SUde  for  Xl-Inch 
Gun-carriage. 

Note. — All  metal  parts  are  composition,  except 
bo  us. 


METAL  PARTS. 

5.  Transporting  journals. 

6.  Pivot-plates  & guide-flanges. 
7 Middle  roller 


screw  and  bracket- 


the  axles,  levers,  elevating 


921.  The  Compressor,  214),  is  placed  upon  the  project- 

ing portion  of  the  Front  Transom  B,  and  is  worked  by  means  of  a 
screw  and  handles,  binding  the  transom  and  compressor-batten  D, 
closely  together,  by  which  the  recoil  is  restrained,  and  kept  with- 
in the  limits  of  the  slide.  On  the  rear  transom  is  placed  a metal 


332 


NAVAL  ORDNx\NCE  AND  GUNNERY. 


saucer,  L,  on  wliich  the  lower  end  of  the  Elevating  Screw,  K, 
rests,  the  upper  portion  working  in  the  cascabel  of  the  gun. 

922.  The  Slide  consists  of  two  wooden  rails,  C,  jogged  into 
transoms,  front,  middle,  and  rear  (E,  Fig.  21d),  and  connected 
beneath  by  slots,  and  at  their  ends  by  cross-pieces  called  Hurters. 
(F,  Fig.  214.) 


CARRIAG-E. 

WOODEN  PADTS, 

J.  Breast  Transom  scored  for  elevation, 

as  is  also  the  middle  transom. 

XTET.AL  PARTS. 

K.  Elevating  Screw. 

L.  Saucers. 

K.  Inside  journal-plate. 

0.  Bracket-bolts, 


SLIDE. 

METAL  PARTS. 

P.  Bossed  Sockets,  Plates,  & Pivot  Bolts. 

R.  Middle  Training  Truck,  with  Journals. 

S.  Transporting  Trucks,  Axles,  «S:  Journals. 

T.  Guide  Plates  inside  of  rails. 


Fig.  213. — Sectional  Vie-w  of  XI- 
Inch  Gun-carriage  and  Slide. 


The  transoms,  E,  three  in  number,  project  beyond  the  slide- 
rails,  and  have  attached  to  them  rollers,  G,  on  eccentric  axles ; 


GUN-CAEKIAGES. 


333 


the  rear  for  training,  ancf  the  front  for  shifting  the  slide,  or 
traversing  it.  At  the  proper  position  in  each  of  the  transoms, 
front  and  rear,  is  placed  a metal  plate,  with  hole  for  the  pivot- 
bolt  (Fig.  211),  6. 

923.  The  Compressor  Battens^  D (Fig.  211),  are  two  strips  of 
oak  equal  in  length  to  the  distance  between  pivots,  which  are 
attached  to  the  slide-rads,  C,  on  the  outside ; against  these  the 
under  lip  of  the  compressor,  f,  takes  when  set  taut. 


Fig.  213. — Pivot  Compressor. 

924.  The  Ilurters^  F,  are  the  two  cross-pieces  bolted  to  the 
rails,  and  haAng  their  inner  sides  curved  for  the  carriage- 
rollers  to  run  against,  should  the  carriage  get  beyond  control, 
going  out  or  in.  To  these  and  the  slide  are  attached  composition 
eyes  for  the  blocks  of  the  in-and-out  training  and  traversing 
tackles. 

923.  Metal  Tracks  are  laid  upon  the  deck  for  the  slide-roll- 
ers, G and  II  (Fig.  214),  to  run  upon,  being  struck  with  a radius 
equal  to  the  distance  between  their  rollers  and  the  opposite 
pivot.  For  each  position  of  the  slide,  in  traversing^  bossed 
sockets,  P (Fig  212),  are  inserted  in  the  deck  for  the  front  and 
rear  pivot-bolts. 

926.  The  Bossed  SocketyY  (Fig.  212),  consists  of  a raised 
rim  of  metal  around  the  pivot-hole,  a corresponding  slot  in  the 
slide  transom  securing  the  coincidence  of  the  hole  in  the  slide 
with  that  in  the  socket,  thus  facilitating  the  entrance  and  re- 
moval of  the  pivot-bolt,  W. 

927.  The  Eccentrics  y G-  and  FL  (Fig.  214),  when  out  of  action 


334 


NAVAL  ORDNANCE  AND  GUNNERY. 


allow  the  slide-transoms,  E,  to  rest  upon  the  deck,  and  those  of 
the  carriage  upon  the  slide.  In  order  to  ti-ain  or  shift  the 
slide,  the  levers  are  shipped  upon  their  axles,  the  rollers,  G and 
H,  put  in  action,  thus  lifting  the  slide  from  the  deck,  and  leaving 
it  free  to  be  moved  by  its  tackles.  In  the  same  way  the  car- 
riage is  lifted  from  the  slide  to  run  in  or  out. 

928.  Recoil. — Before  firing,  the  compressor,  f,  is  set  taut  by 
the  screw,  binding  the  carriage  transom,  B,  and  compressor- 
batten,  D,  together.  When  the  gun  is  fired,  the  recoil  is  ab- 
sorbed by  the  friction  exerted  between  them. 

929.  The  Compressors,  f (Figs.  213  and  211),  are  not  intended 
to  eiitii’ely  supersede  the  use  of  breechings,  but  rather  as  an  aux- 
iliary ; the  main  reliance  being  placed  on  the  Breeching,  which 
should  be  shackled  to  the  ship’s  side,  and  not  to  the  slide,  as  in 
the  latter  position  unnecessary  strain  is  brought  on  the  pivot- 
bolt. 


CARRIAGE. 


WOODEN  PARTS.  METAL  P.VETS. 

A.  Brackets  of  two  pieces,  with  jog,  d.  Cap  Squares. 

a,  and  dowels,  b.  e.  Trunnion  Plates. 

B.  Transoms,  projecting  beyond  the  f.  Compressor,  with  screw  and  lever, 
rails,  front,  middh',  and  rear,  g.  Rollers  and  Journal  Plates, 
jogged  into  brackets. 

SLIDE. 

WOODEN  PARTS.  MET.VL  P.VRTS. 

C.  Rails.  , U-  Shifting  Trucks. 

D.  Compressor  Battens.  H.  Training  Trucks,  both  uith  jour- 

E.  Transoms  ; front  and  rear,  each  nals,  and  eccentric  axles, 
in  two  parts,  middle  in  one  part. 

F.  Hurters,  front  and  rear. 


Firing  to  Windward,  the  compressor,  f,  should  be  set  just 
taut  eiioiurh  to  check  the  recoil  and  ease  the  strain  on  the 

O 

breeching. 


GUN-CARRIAGES. 


335 


Firing  to  Leeward^  the  gun  on  recoil  has  to  run  up  an  in- 
clined plane ; consequently  the  compression  required  is  very 
slight. 

^YitK  the  Yessel  on  an  Even  Keel,  it  is  usual  to  set  tlie 
Compressor  a certain  number  of  turns,  which  is  known  to  give 
the  proper  compression. 

930.  Shipping  the  Levers. — In  order  that  this  may  be  done 
expeditiously,  both  axle  and  lever  are  marked  with  a cold- 
chisel,  and  should  always  be  hove  up  past  the  centre  and  rest 
against  the  wood  of  the  slide  or  carriage. 

931.  Transporting. — For  transporting  the  pivot-carriage  and 
slide  f]-om  one  end  of  a vessel  to  the  other,  composition  sockets, 
S,  are  attached  to  the  under  side  of  each  slide-rail ; through 
these  pass  square  axles,  carryiiig  at  their  extremities  metal 
rollers.  The  axle,  being  passed  through  the  slide,  is  lifted  on  its 
rollers,  the  transporting  trucks  shipped,  and  the  slide  lowered ; 
it  now  rests  on  the  transporting  trucks,  S,  and  may  he  readily 
moved  to  any  desired  position.  (5,  Fig.  211.) 

A Middle  Roller,  7 (Fig.  211),  has  in  some  cases  been  pro- 
vided for  the  slide  of  the  Xl-ineh  gun,  which  from  its  great 
length  is  liable  to  sag  at  the  centre. 

932.  Running  out  to  Leeward  in  a sea-way,  even  with  pre- 
cautions and  a well  drilled  crew,  there  is  liability  of  the  gun 
breaking  away  and  doing  damage.  To  guard  against  this. 


Fig.  216. 


Preventer  Breechings,  T,  are  fitted  (Fig  210),  of  such  a 
length  as  to  he  just  taut  when  the  gun  is  out,  and  allow  the 
front  carriage  trucks  to  reach  but  not  ascend  the  curve  of  the 
front  hurter,  F ; for  if  the  trucks  should  ascend  this  curve,  the 
compressor-straps  must  surely  give  way  to  the  power  exerted  to 
separate  the  carriage  and  slide  by  such  a heavy  weight  moving 
with  its  velocity. 


3G 


NAVAL  ORDNANCE  AND  GUNNERY. 


933.  XI-iNCH  Ikon  Pivot-Cakeiage. — 


Nomenclature. 


A.  — Slide  rails. 

B.  — Transoms. 

C. — Front  and  Rear  Hurters. 

D.  — Pivot-holes. 


SLIDE. 

E.  — Transporting  Trucks. 

F.  — Slide  Rollers. 

1,  2,  ?}. — Tie  Bolts. 

4. — Transporting  Axle. 


CARRIAGE. 


G. — Brackets. 

II. — Front  Bed-plate. 

I. — Bear  Bed-plate. 

K.  — Eccentric  Rollers. 

L.  — I'ront  Rollers. 

M.  — Cap  Square. 

N.  — Composition  plates  to  increase 

friction. 


O.  — Angle  iron  connecting  brackets, 

etc. 

P.  — Bolts  for  Preventer  Breeching. 

Q — Compressor  Plate. 

R.  — Bolts  of  In-and-Out  Tackles. 

S.  — Vertical  Transom. 

P'.  P'. — Journal  Plates.  V Compressor, 


PRINCIPAL  DIJIENSIOXS. 


Extreme  length 15  ft.  7 in. 

Length  between  Pivots 11  ft.  10  in. 

Width  of  Slide 3 ft.  G in. 

Width  of  Rails 0 ft.  5 in. 

Radius  of  Training  Track 10  ft.  10  to, 

Radius  of  Traversing  Track 12ft.  G in. 


934.  The  Slide,  A,  consists  of  two  rails  of  double  T rolled 


wroiiglit-iron,  8.87  inches  high  by  5 inches  wide,  connected  by 
the  tie-bolts,  1,  2,  3. 


GTJIT-CAERIAGES. 


337 


935.  Hie  Transoms,  B,  are  of  1-^ineli  wroiiglit-iroTi  of  the 
form  shown  in  the  figm’e,  and  riveted  to  the  under  side  of  the 


rails,  A ; they  project  beyond  and  have  fitted  to  them  composi- 
tion rollers,  F,  on  eccentric  axles,  the  latter  being  secured  by 
plates  and  iDolts  ; levers  shipped  on  the  projecting  ends  of  the 
axles  put  the  rollers  in  and  out  of  action. 

936.  The  Hurters,  (7,-are  the  brass  castings  riveted  to  each 
end  of  the  slide-rails  for  the  carriage-trucks  to  run  against.  Each 
of  these  carries  bolts  for  the  blocks  of  the  in-and-out  tackles  he- 


338 


NAVAL  ORDNANCE  AND  GUNNERY. 


neath  them,  and  to  the  vertical  part  of  the  T rail,  are  attached 
brass  plates  with  bolts  for  the  blocks  of  the  shifting  and  train- 
ing tackles. 

937.  Coincidence  of  the  Pi/oot-holes,  D,  is  secured  by  plates 
screwed  to  the  slide  transoms,  B,  and  distant  from  each  other 
a little  more  than  the  diameter  of  the  bossed  socket,  indicated  in 
the  figure  by  the  dotted  circle  around  the  pivot-hole,  D. 

938.  Fo7‘m  of  Bail. — The  wrought-iron  rails.  A,  when  first 
manufactured  have  the  form  shown  in  Fig.  215,  but  before  be- 
ing placed  for  the  slide  the  under  side  of  the  upper  outer  por- 
tion of  the  T is  removed,  giving  it  the  form  of  Fig.  216,  in 
order  that  the  compressor  may  have  a fiat  surface  to  act  on. 

939.  Transporting. — Aboiit  ten  inches  in  rear  of  the  front 
and  the  same  distance  in  front  of  the  rear  trucks  are  placed  the 
sleeves  for  the  transporting  axle  and  trucks,  E,  the  latter  of 
such  a diameter  as  to  sustain  the  slide  clear  of  the  deck  when 
let  down  from  its  eccentric  rollers,  F. 

940.  The  Carriage. — All  iron  parts  of  the  carriage  are  made 
of  1-J-ineh  wrought-iron,  the  journal-plates,  rollers,  eap-scpiare, 
trunnion-rests,  and  preventer-breeching-bolts  being  of  brass. 

Immediately  beneath  the  trunnion-hole  is  a vertical  iron 
plate,  S,  extending  down  between  the  brackets  to  the  bed- 
plate, II. 

941.  The  Brackets,  G-,  rest  on  the  bed-plates,  and  they  and 
the  vertical  transom,  S,  and  bed-plates,  II  and  I,  are  riveted 
together  with  the  angle  iron,  O. 

942.  The  Bed-plates,  II  and  I,  extend  beyond  the  brackets, 
the  rear,  I,  being  shaped  to  a doiible  eye,  for  the  blocks  of  the 
in-and-out  tackles,  the  front,  II,  contracting  into  a plate  for  the 
compressoi-screw  to  work  upon. 

943.  The  Journal  Plates,  P',  for  the  eccentric  axle  and 
rollers  are  riveted  to  the  rear  end  of  the  brackets,  G,  the  axle 
extending  across,  between,  and  beyond  the  plates  and  carrying 
rollers,  K,  revolving  in  the  jfiates.  These  axles  are  eccentric  in 
order  that,  by  the  use  of  level’s,  the  trucks  may  be  placed  in  or 
out  of  action  at  pleasure.  In  the  former  ease  the  carriage  is 
raised  and  rests  on  its  rollers,  K ; in  the  latter,  it  rests  on  the 
slide,  A. 

944.  Form  of  Eccentric  Axle. — An  ordinary  cylindrical  axle 

has  cast  on  it  an  eccen- 
tric (Fig.  219),  that  is, 
instead  of  the  two  cylin- 
ders being  concentric, 
the  axle  passes  on  one 
side  of  the  centre,  X,  of 


Fig.  219. 


GUiSr-CAERIAGES. 


339 


the  larger  circle.  "With  the  axle  at  its  lowest  position,  the  rollers 
are  out  of  action  ; at  its  upper  position,  the  carriage  is  raised  by 
the  action  of  the  rollers,  a height  corresponding  to  the  eccen- 
tricity of  the  axle. 

The  front  trucks,  L,  are  like  those  of  an  ordinary  carriage, 
always  resting  on  the  slide  and  revolving  on  any  movement  of 
the  carriage. 

9d5.  The  Compressor^  Y (Fig.  220),  consists  of  a composi- 
tion casting,  Y,  having  a vent,  V',  at  the  centre  of  the  upper 
arm,  through  which  works  a screw  bolt,  W,  with  handles. 
It  is  placed  on  the  compressor  plate,  O,  its  under  lip,  x,  taking 
against  the  under  side  of  the  upper,  T,  of  the  rail.  When  the 


« ib". 


screw  is  turned,  the  rail  is  compressed  between  the  compressor 
plate,  O,  and  the  lip  of  the  compressor,  x.  The  recoil  is  thus 
limited  by  the  friction  of  the  different  parts. 

946.  Recoil. — As  the  bed-plates,  II  and  I,  and  rail  are  each 
of  iron,  acting  alone,  sufficient  friction  would  not  be  excited  to 
keep  the  recoil  within  the  desired  limits.  To  correct  this  deti- 
ciency,  after  the  brackets,  G,  have  been  riveted  to  the  bed-plates, 
plates  of  composition,  1ST,  are  screwed  to  that  portion  of  the  bed- 
plates in  contact  with  the  slide,  thus  increasing  the  friction  to 
the  required  point.  As  the  compressors  are  placed  as  near  as 
possible  to  the  brackets,  the  latter  are  cut  out  to  allow  space  in 
turning  the  handles  of  the  compressor. 

947.  Necessitij  of  Eccentric  Rollers  in  the  Slide.— 
slide-rollers,  F,  are  all  eccentric  for  the  reason  that  when  shift- 
ing the  slide  at  sea,  with  much  motion  on  the  ship,  it  is  abso- 
lutely necessary  to  have  complete  control  of  it ; for  should  it 
once  get  away  from  the  crew,  it  becomes  a serious  matter  to 
again  confine  it. 

When  this  is  likely  to  occur,  the  levers  are  at  once  let  down, 
throwing  the  rollers  out  of  action  and  the  slide  upon  the  deck, 
when,  from  the  great  weight,  the  friction  of  the  transoms  on  the 


340 


NAVAL  OEDNANCB  AND  GUNNERY. 


deck  will  almost  immediately  stop  it.  This  would  be  impossi- 
ble were  the  slide  always  free  to  move  on  its  roUerSj  and  only 
confined  by  tackles.  ^ 

948.  20-pde.  Eifle  Pivot  Caeeiage. — 


Principal  Dimensions. 


Estreme  length f)7  inches. 

Length  between  Pivots 88  inches. 

Width  of  Slide 23.G  inches. 

Thickness  of  iron. f inch. 

Radius  of  Training  Track 83  inches. 

Radius  of  Shifting  Track 90  inches. 

Extreme  length  of  Carriage 48  inches. 


Its  construction  is  essentially  the  same  as  the  Xl-inch  car- 
riage, the  only  difference  being  that  the  bed-plates  of  the  twen- 
ty-pounder are  of  bronze  cast  with  two  upright  pieces,  to  which 
the  iron  bi’ackets  are  riveted,  while  in  the  Xl-inch,  angle  iron  is 
used  to  connect  their  brackets  and  bed-plates.  Only  one  tie  bolt 
is  used  to  connect  the  slide-rails  at  their  centres.  As  the  beds 
are  of  bronze  the  requisite  amount  of  friction  can  always  be 
obtained  by  the  compressor.  (Figs.  221  222.) 

949.  XY-iNcn  Tukket  Carriage. — ■ 


Nomenclature. 


a. — Box  Bracket. 

B.  — Bed  Plate. 

C.  — In-and-out  gear. 

D.  — Compressor. 

E.  — Cog-wheel. 

F.  — Guides. 

G.  — Carriage-braces. 

II. — ‘‘  RoUers. 

I.  — Iron  rails. 


K. — Balance-wheel. 

L ' . — El  e vator-  rest. 

M.  — Curved  lever. 

N.  — Front  Transom. 

O.  — Rear  “ 

O'. — Sleeve. 

O”.— Nut. 

P. — Small  Cog- wheel 
R. — Compressor  Plates. 


GUN-CAERIAGES. 


341 


950.  The  Slide  consists  of  two  heavy  iron  rails,  I,  extend- 
ing from  one  circumference  of  the  Tm*ret  to  the  other,  and 


firmly  secured  to  it ; on  these  run  the  carriage  rollers,  II.  Be- 
tween the  two  iron  rails,  and  parallel  to  them,  are  four  wooden 
joists,  L,  called  compressor-battens,  each  six  inches  square.  (Fig. 
225.) 

951.  The  Carriage  is  of  wrought-iron.  The  brachets.  A, 
being  of  the  box  form,  while  the  bed-plate,  B,  and  front,  N, 
and  rear  O,  transoms,  are  of  single  plate-iron.  All  parts  of 
the  carriage  being  riveted  together,  and  the  brackets.  A,  sup- 
ported by  the  two  traces,  G.  At  each  under  corner  of  the  bed- 
plate, B,  is  placed  an  angular  metal  plate,  F,  called  a guide,  pre- 
venting lateral  motion  of  the  carriage  on  the  rails. 

952.  The  Li-and-Out  Gear,  C,  consists  of  an  axle  extend- 


34:2 


NAVAL  ORDNANCE  AND  GUNNERY. 


ing  across  the  front  end  of  the  carriage,  caiTjing  rollers,  H, 
placed  in  the  brackets.  Just  inside  the  outer  bracket,  the  axle 


lias  on  it  a large  cog-wheel,  E,  a shorter  axle  placed  hio-her  in 
tlie  bracket,  working  the  larger  cog-wheel  bj  means  ”of  the 


smaller  cog,  P,  in  its  inner  end.  To  the  outer  end  is  fixed  a 
crank,  C',  to  be  worked  by  hand. 

953.  The  Carriage  Rollers,  II,  are  four  in  number : the  for- 
ward two  attached  to  the  axle  of  the  “ In-and-Out  Gear,”  and 
the  rear  to  short  axles  in  each  bracket. 


GUN-CAERIAGES. 


343 


954.  The  Compressor  Gear,  D.— To  the  bottom  of  the  carriage 
is  piveted  an  iron  plate  (P.  Fig.  225),  whose  ends  project  doAvn- 
ward  through  the  Bed-plate,  B ; on  these  are  hung  curved 
levers,  M.  To  one  is  pivoted  a sleeve.  O',  and  to  the  other  a 
nut,  O".  A rod  passing  through  the  bracket  and  the  sleeve  has 
on  its  end  a thread,  which  works  in  the  nut  on  the  opposite 
lever ; lateral  motion  of  the  sleeve  on  the  rod  being  prevented 
by  collars  outside  the  bracket.  The  rod  has  attached  to  it  a bal- 
ance-Avheel  and  crank,  K. 

955.  The  Compressor  Plates,  R,  five  in  number,  are  of  ^ 
inch  iron  (Fig.  224) ; their  ends  project  through  the  Bed-plate  and 
are  keyed  ; tlieir  lower  portions  extending  downward  between 
the  wooden  joice  or  battens,  L (Fig.  225),  parallel  with  them 
and  the  iron  rails. 

956.  Action  of  the  Compressor  Gear. — As  the  balance- 


wheel,  K,  is  revolved  it  carries  the  rod  with  it,  causing  the 
upper  ends  of  the  curved  levers,  M,  to  separate,  and  the  lower 
to  approach  ; the  latter  press  against  the  two  outer  compressor- 
battens,  L,  forcing  them  out  of  parallelism,  and  binding  the 
iron  plates,  R,  and  battens,  L,  firmly  together.  When  the  gun 
is  fired  its  recoil  is  absorbed  by  the  friction  of  the  several  parts. 
Reversing  the  motion  of  the  wheel  separates  the  plates  and 
battens,  leaving  the  carriage  free  to  move  on  its  rollers. 

957.  Elevator-Pest. — Idie  elevating  screw  usually  rests  on 
the  projecting  portion,  L',  of  the  bed-plate.  In  some  carriages  a 
semicircular  plate  is  riveted  to  the  rear  transom,  having  on 


344 


ORDNANCE  AND  GUNNERY. 


its  circnmference  a vertical  plate  connected  to  a fore  and  aft 
plate,  tlie  two  supporting  an  iron  saucer,  on  whicli  the  lower 
end  of  the  elevating-screw  rests,  the  upper  end  passing  through 
the  cascahel  of  the  gun. 

958.  The  Ilurters  are  flat  plates  of  iron  bolted  to  the  rails,  to 
prevent  the  carriage  going  beyond  the  proper  point,  out  or  in. 

959.  Ele/vation. — The  port  is  cut  from  the  circumference, 
of  the  turret,  of  such  dimensions  as  to  allow  of  10°  elevation 
and  5°  depression,  and  permit  only  vertical  motion  of  the 
muzzle  of  the  gun  in  it. 

960.  The  Port  Stopper,  S (Fig.  226). — ^When  the  gun  re- 
coils after  firing,  the  open  poi't,  Z,  is  free  to  the  entrance  of 
an  enemy’s  shot.  To  protect  those  in  the  turret  while  loading 
the  gun,  a heavy  mass  of  iron,  S (Fig.  226),  curved  to  allow  the 
gun  to  pass  going  in  and  out,  is  pivoted  at  the  top  and  bottom 
of  the  Turret,  and  worked  by  a lever  and  tackle.  As  the  gun 
recoils,  the  Port  Stopper  is  swimg  around,  covering  the  port, 
and  swinging  sufliciently  near  to  the  inner  circumference  of  the 
Turret  to  prevent  shot  fired  at  an  angle  from  entering  the 
Turret  between  it  and  the  port.  The  gun  being  loaded  the 
port-stopper  is  swung  around  and  the  gun  run  out. 

961.  Loading. — The  loading  hatches,  T,  are  placed  abreast 
the  rear  of  each  carriage  when  in,  the  communication  between 
the  turret  and  below  being  open  when  the  guns  are  pointed 
abeam.  As  the  projectiles  are  very  heavy  and  the  space  in  the 
turret  limited,  mechanical  appliances  are  made  use  of  to  carry 
the  projectile  to  the  muzzle  of  the  gun.  These  consist  of  a long 
iron  rod,  U,  pivoted  above  the  loading-hatch,  the  movable  end 
being  fitted  to  slide  on  a guide  at  the  top  of  the  turret  abreast 
the  muzzle  of  the  gun.  The  shell-tackle  is  hung  on  the  ]’od  by 
its  strap,  which  carries  a roller  travelling  on  the  rod.  When 
the  gun  is  to  be  loaded,  the  shell  is  whipped  u]^  to  the  requisite 
height,  the  whip  hitched,  and  the  projectile  run  to  the  muzzle 
of  the  gun  on  the  rod.  After  each  tire,  the  turret  is  revolved  so 
as  to  bring  the  gun  abeam  and  leave  the  loading-hatches  open. 

962.  The  Hammer  and  Sponge. — The  port  being  closed 
by  the  port-stopper,  S,  an  ordinary  handle  cannot  be  used, 
hence  that  in  use  consists  of  a number  of  sections  which  con- 
nect with  each  other  by  a spring  catch.  The  rammer  or  sponge, 
beiirg  fixed  to  the  first  section,  is  entered  and  the  next  section 
prrt  on  ; in  this  way  the  whole  is  made  up  and  the  gun  sponged 
or  the  projectile^  pushed  home.  In  removing  the  sjronge  or 
rammer,  each  section  is  taken  off  as  its  catch  comes  to  the 
muzzle. 

963.  Pointing. — The  guns  being  fixed  in  the  tuiTet,  point- 


GUN-CAIIRIAGES. 


345 


ino-  is  effected  by  revolving  it  until  the  guns  bear  upon  tlie  ob- 
ject, which  is  determined  by  the  person  at  the  sight-hole,  T. 


This  consists  of  a circular  opening  of  about  two  and  a half  or 
three  inches  diameter  cut  through  the  turret,  parallel  to  the  rails 


346 


NAVAL  ORDNANCE  AND  GUNNERY. 


on  which  the  carriage  runs.  In  this  opening  is  placed  an  in- 
strument (Fig.  227),  consisting  of  a hollow  cylinder  of  brass, 


having  a portion  of  its  circumference  at  the  outer  end  cutaway, 
and  a vertical  piece  soldered  to  it.  The  inner  end  of  the  cyl- 
inder is  closed,  and  a vertical  slit  cut  in  it.  The  officer  at  the 
sight-hole,  loohing  through  the  sHt,  brings  the  vertical  piece  on 
the  object,  when  the  engineer  at  the  starting-bar  ceases  to  re- 
volve the  turi'et. 

964.  Sights. — The  gun  besides  being  fitted  with  the  ordi- 
nary sight  has  a trunnion-ledge  and  level  (Fig.  228).  This  con- 


Fig.  228. — Trunnion-ledge  and  Level  for  XV-incli  Gun. 

sists  of  a brass  plate  pivoted  to  the  centre  of  the  trunnion,  the 
upper  portion  ending  in  a pointer,  the  lower  having  a slot  and 
thumb-screw  working  in  it.  A ledge  projects  from  the  plate, 
on  which  is  placed  a spirit-level.  The  upper  face  of  the  trun- 


GUN^-CAEIIIAGES. 


347 


nion  is  graduated  for  a certain  number  of  degrees  of  elevatiou 
and  depression. 

To  elevate  the  gun,  loose  the  thumb-screw  and  move  the 
pointer  to  the  number  of  degrees  desired  ; tighten  the  screw  and 
lower  the  breech  until  the  bubble  of  the  spirit-level  marks  zero. 
The  gun  then  has  the  elevation  indicated  by  the  pointer ; re- 
versing the  operation,  depression  is  obtained. 

965.  The  Turret  when  not  in  use  rests  upon  the  deck,  a 
raised  rim  of  metal  protecting  its  lower  edge  from  being 
jammed  by  shot.  A.  shaft,  L,  passes  down  through  the  vessel 
to  the  kelson,  with  arrangements  at  its  lower  end  for  being 
raised  by  a wedge  and  ram.  When  this  is  done  the  turret  is 
raised  from  the  deck  and  rests  on  the  shaft,  and  is  revolved  by 
steam  gearing.  The  turret  is  composed  of  a number  of  one- 
inch  wrought-iron  plates,  firmly  bolted  together,  making  a total 
thickness  from  eleven  to  thirteen  inches.  The  people  in  the 
turret  are  protected  from  the  fastening  bolts,  which  ai-e  likely 
to  fly  out  on  the  impact  of  heavy  shot,  by  a casing  of  iron 
placed  a few  inches  from  the  inner  circumference  of  the  turret. 

966.  Above  the  turret  is  placed  an  iron  pilot-house,  from 
which  those  controlling  the  movements  of  the  vessel  may  see 
by  the  bevelled  openings  in  its  circumference.  In  some  moni- 
tors the  guns  and  their  carriages  have  been  arranged  to  work 
by  steam,  and  the  turret  to  be  raised  by  an  hydraulic-pump  at- 
tached to  the  lower  end  of  the  shaft,  instead  of  the  wedge  and 
rams.  This  would  seem  to  be  a decided  improvement  over  the 
old  method,  or  that  generally  in  use. 

967.  Moktae  Caekiage  (Fig.  229). 


Nomenclature. 


1.  — Circle. 

2.  — Bracket. 

8. — Mortar. 

4 — Face. 

5.  — Trarmion. 

6.  — Carriage  Steps. 

7.  — Eccentric  Socket. 

8.  — Carriage  Boiler. 

9.  — Circle  Eccentric. 


10. — Hurter. 

11.  — “Ratchet. 

12.  — Clovis  lug. 

18. — Stringers. 

14.  — Rear  Transom. 

15.  — Heavy  Cro.ss-bolt. 
IG. — Lever  (eccentric). 

17.  — Circle-lever. 

18.  — Guides. 


Principal  Dimensions. 


Length  of  Carriage 9 ft.  4 inches. 

IVidth  of  Carriage,  Front 4 “ 9 “ 

Vv'idth  of  Carriage,  Rear 4 “ G “ 

Height  of  Trunnion 3 “ 2 “ 

Diameter  of  Circle 11  “ G “ 


968.  The  Carriage. — In  consequence  of  the  high  angles  at 
which  mortars  are  fired,  their  carriages  differ  from  ordinary  gun- 


348  NAVAL  ORDNANCE  AND  GUNNERY. 

carnages  in  tliat  they  rest  for  their  whole  length  on  the  circle 
or  platform. 

969.  The  Brackets,  2,  are  each  made  of  two  pieces  of  boiler- 
iron,  separated  from  each  other  by  flat  bars  of  iron  placed  at 
suitable  intervals,  to  stiffen  the  brackets  in  the  direction  in 
vdiich  the  weight  and  recoil  bear  upon  them.  All  parts  are 
held  together  by  screw-bolts.  The  brackets  are  united  to  each 
othei  by  the  steps,  6,  axle-tree,  8,  two  ii’on  stringers,  13,  crossing 


20 

Fig.  229. 

diagonally  under  the  piece  near  the  bottom  of  the  brackets,  a 
rear  transom,  14,  and  a heavy  cross-bolt,  15. 

970.  27ie  Transoms. — The  steps,  6,  serve  the  purpose  of 
front  transoms,  and  are  made  by  laying  plates  of  boiler-iron  hor- 
izontally ; the  lower  being  nearly  twice  the  size  of  the  upper, 
and  bolted  to  the  brackets.  The  upper  is  scored  out  in  the 
rear  to  allow  for  the  curved  form  of  the  piece.  The  rear 
transom,  14,  is  a plate  of  iron  placed  vertically  between  the 
brackets  in  rear  of  the  piece,  and  is  fitted  with  an  elevating 
loop,  which  serves  as  a fulcrum  for  the  elevating  lever. 

971.  llunning In  and  Out. — The  motion  of  the  carriage  in 
running  in  or  out  is  obtained  by  a pair  of  rollers,  8,  on  an  eccen- 
tric axle,  placed  underneath  and  a little  in  front  of  the  curve 


GTJiSr-CAKRIAGES, 


319 


of  the  ti’unnions.  On  the  projecting  end  of  the  axle  a lever, 
16,  ships,  by  which  the  rollers  may  be  thrown  in  or  out  of  ac- 
tion. The  motion  of  translation  of  the  carriage  is  given  by 
handspikes  placed  in  holes  in  the  circumference  of  the  trucks, 
8 ; the  latter  being  first  thrown  in  action  by  the  lever  in  the 
socket,  7,  The  movements  of  the  carriage  are  directed  by  com- 
position guides,  18,  screwed  to  the  circle  and  fitting  over  flanges 
at  the  bottom  of  the  brackets.  A heavy  piece  of  oak,  called  the 
Hurter  bolted  to  the  circle,  limits  its  outward  movement,  the 
brackets  being  curved  to  fit  the  slope  of  the  hurter. 

972.  The  Mortar  Circle,  (Fig.  230). — The  naval  mortar  is 


, Fig.  230. 

generally  used  on  board  schooners  built  for  the  purpose.  It  is 
carried  amidships,  and  that  part  of  the  deck  on  which  the  cir- 
cle rests  is  raised  about  three  inches  above  the  remainder.  The 
circle  is  a circular  platform  made  by  two  thicknesses  of  oak 
beams ; the  upper,  called  the  deck  planks,  are  laid  at  right  angles 
to  the  direction  of  the  recoil ; the  lower  layer,  called  sleepers, 
being  laid  parallel  to  the  axis  of  the  piece.  The  two  layers  are 
bolted  to  each  other  horizontally  and  vertically,  and  strength- 


350 


NAVAL  ORDNANCE  AND  GUNNERY. 


ened  circumferentially  by  two  steel  hoops,  19  and  20,  one  at 
the  top  and  bottom.  This  disposition  of  the  planks  offers  the 
greatest  resistance  to  recoil.  On  its  upper  surface  are  bolted 
composition  tracks,  22,  for  the  carriage  rollers.  A heavy  bolt 
through  its  centre,  working  in  a frame-work  beneath,  keeps  it  in 
position. 

973.  Eaentric  Rollers  (23)  are  four  in  number,  and  placed 
at  equal  distances  in  the  circumference  of  the  circle.  (3n  the 
ends  of  the  axles,  curved  levers  (IT)  ship,  by  which  the  circle 
is  raised  on  its  rollers,  and  may  be  revolved  about  its  central 
pivot  by  tackles  hooked  to  eye-bolts  in  the  circle  and  deck. 

971.  The  Deck  is  strengthened  underneath  the  circle  by  a 
column  of  heavy  beams  laid  across  each  other,  and  extending 
from  the  kelson  up  to  the  under  side  of  the  deck. 

975.  Howitzer  Boat-carriage.  (Wood.) 


Fig.  231. 
Nomenclature. 


A. — Bed. 

B. — Slide. 

C.  — Compressor  Plate. 

D.  — Compressor  Bolts. 

E.  — Compressor  Handlea. 

F.  — Lugs  for  Loop. 


G.  — Bed-plate. 

H.  — Elevating  Serew. 

K — Ath wart-ship  Sweep 

L.  — Pivots. 

M. — Pivot  Plates. 

N.  — Fore  and  aft  Sweep  Piece. 


' 976.  The  Slide  consists  of  a wooden  top-piece  resting  on 
two  side  pieces  tvliich  are  slightly  inclined  from  the  vertical 
and  slope  at  each  end  towards  the  end  of  the  top-piece,  where 
metal  plates  are  attached  for  the  pivot-bolts,  of  the  carriage. 
In  the  top-piece,  and  extending  iiearly  its  whole  length,  is  a 
slot  in  which  move  the  bolts,  D,  and  wooden  guide  of  tlie  Bed- 
plate. The  bolts,  1),  are  square  at  their  lower  ends  and  pass 
through  the  bed-plates,  up  the  slot,  and  through  the  bed,  A. 
On  their  upper  ends  a thread  is  cut,  and  corresponding  nuts 


GTm-CAEEIAGES. 


351 


■with  handles,  E,  work  on  a composition  plate  let  into  the  wood, 
flush  with  it.  On  this  the  nuts  press  when  screwed  down, 
compressing  the  slide,  B,  between  the  bed.  A,  and  bed-plate, 
G,  and  controlling  the  recoil  by  the  friction  of  the  difi'erent 
parts. 

977.  The  Compressor  is  composed  of  the  several  parts  C, 
D,  E,  G,  and  A ; that  is,  it  consists  of  a combination  of  all, 
resulting  in  friction  between  certain  parts  and  modiflcation  of 
the  recoil.  When  the  compressor  handles  are  set  as  taut  as  the 
strength  of  an  ordinary  man  will  allow,  it  always  suffices  to 
keep  the  recoil  within  the  limits  of  the  stop  in  the  slide.  In 
order  that  the  compressors  shall  invariably  perform  their  func- 
tion, the  surface  of  the  parts  in  contact  must  be  plain  but  not 
smooth. 

The  Bolts,  D,  being  passed  through  the  bed-plate  loosely, 
were  the  handles  taken  off,  they  would  drop  out ; to  prevent 
this,  small  buttons  are  placed  on  the  under  side  of  the  bed- 
plate, G. 

The  Lugs,  E,  are  cast  of  composition  ■with  a cavity  to  re- 
ceive the  loop  of  the  gun,  which  rests  in  it,  and  is  retained 
there  by  a bolt  passing  through  the  lug  and  loop ; the  latter 
being  secured  by  a pin  and  washer. 

978.  Elevation  is  obtained  by  a screw,  II,  passing  through  the 
caseabel  of  the  gun ; its  lower  end  has  a knob  Avorking  in  a 
box  fitted  to  the  bed;  a disk  a few  inches  above  the  knob  serves 
to  turn  the  screw. 

979.  The  Boat-carriage  should  be  so  placed  in  the  bow  of 
the  boat  as  to  carry  the  muzzle  of  the  Howitzer  just  above  and 
clear  of  the  gunwale  and  stern  of  the  boat.  Two  pieces  of 
yellow  pine,  K,  are  laid  athwart-ships  so  as  to  bear  the  carriage 
at  that  height,  and  on  these  it  traverses  when  pivoted  at  the 
stem. 

980.  Pivots. — Six  pivots,  are  pivoted  to  each  boat ; stem, 
each  bow,  stern,  and  each  quarter.  The  tAvo  iron  plates,  M,  of 
each  pivot,  being  Avelded  together  and  bolted  to  their  positions, 
the  distances  between  the  stem  pivot-plate,  and  that  of  either 
bow,  must  correspond  to  the  distances  betAveeu  the  pivot-holes 
in  each  end  of  the  slide ; they  are  thus  at  the  points  of  an 
equilateral  triangle,  which  enables  a rapid  and  certain  manage- 
ment of  the  gun  in  changing  its  position.  (Fig.  232.) 

981.  Pivoting. — If  the  carriage  be  pivoted  at  the  stem,  it 
may  be  brought  to  either  boAv,  by  pi\*oting  the  rear  end  of  the 
slide  to  one  boAv,  remoA'ing  the  stem  pivot,  and  training  the 
forward  end  to  the  opposite  bow ; to  change  it  from  the  bow  to 


352 


NAVAL  ORDNANCE  AND  GUNNERY. 


the  stem  pivot,  the  process  is  reversed.  To  sustain  the  carriage 
when  pivoted  at  the  how  in  sweeping-,  a piece  of  yellow  pine 
scantling,  N,  is  placed  fore  and  aft  amidships  and  mortised  into 
the  rear  cross-pieces. 

The  stern  of  the  boat  is  similarly  arranged,  bnt  from  the 
form  of  the  boat  at  that  part  there  is  more  space,  and  the  gnn 
can  always  be  worked  easier  there  than  forward. 


982.  The  Ikon  Boat-carkiage.— (Fig.  233.) 

Wrouglit-iTon  J3 oat-carriages  are  now  being  made  and 
supplied  to  vessels  in  service,  the  dimensions  being  tlie  same 
as  those  of  the  wooden  carriage,  in  order  that  they  may  replace 
them  and  not  entail  any  change  in  the  present  fittings  of  boats. 


983. 


Nomenclature. 


A. — Slide 

B. — Bed. 

C.  — Bed-plate. 

D.  — Lugs  for  Loop. 


E.  — Elevator  Box. 

F.  — Compressors. 

G.  — Rests  of  Slide. 


Principal  Dimensions. 

Extreme  length 

Length  between  Pivots 

Length  of  Bed 

Length  of  Bed- plate 

Width  of  Bed 

Extreme  width  of  Slide 

Height  of  Loop-bolt 


GSil  inches. 
64.1  “ 

87  “ 

26.3  “ 

7.75  “ 
11.75  “ 
13.05  “ 


981.  The  Slide.  A,  consists  of  a wrought-iron  plate,  riveted 
to  two  wrought-iron  Z-shaped  sides,  the  heads  of  the  rivets 


GUN-CARRIAGES. 


353 


bein^  taken  oS  to  present  a plain  surface  to  tbe  bed,  B.  The 
iipper  plate  of  tbe  slide  contains  a slot  extending  nearly  its 
whole  lena:tb.  Between  the  ends  of  the  slot  and  slide  are  holes 
for  the  front  and  rear  pivot  bolts. 

985.  The  Bed  Plate. — Between  the  side  pieces,  a composi- 
tion bed-plate,  C,  travels  forward  and  back ; to  this  plate  are 
attached  bolts,  having  a thread  cnt  on  their  upper  ends ; these 
pass  through  the  slot  in  the  slide  and  holes  in  the  bed,  and 


0 D \d 

ik 

,u 

Fig.  233. 

have  working  on  them  corresponding  nuts  with  handles  by 
which  the  necessary  compression  of  the  slide  between  the  bed 
and  bed-plate  is  produced,  thus  modifying  the  recoil. 

986.  The  Bed.,  B,  which  rests  on  the  slide,  A,  is  a bronze  cast- 
ing, consisting  of  a plate  having  on  its  upper  surface  projecting 
pieces,  D,  called  the  lugs,  which  have  a cavity  in  them  for  the 
loop  of  the  gun  ; the  elevator  box,  E,  and  holes  for  the  compres- 
sor-screws. 

987.  Fiecoil.—K^i\xQ  slide  is  of  wrought-iron,  while  the  bed 


354 


NAVAL  OEDNANCE  AND  GUNNEET. 


and  bed-plate  are  of  bronze,  advantage  is  taken  of  the  friction 
exerted  between  the  different  metals  to  check  recoil.  This  is 
accomplished  more  effectually  by  having  the  frictional  sur- 
faces of  different  kinds  of  metal,  than  when  only  one  kind  is 
emplojmd. 

988.  The  Sides  curve  upward  at  each  end  to  allow  space  be- 
tween the  carriage  and  pivot-plate,  and  to  facilitate  its  move- 
ments. 

By  reference  to  the  rear  elevation  of  the  carnage  (Fig  233;, 
the  manner  of  riveting  the  top  plate  to  the  Z-shaped  sides  will 
be  readily  understood,  and  that  the  slide  rests  on  the  lower  por- 
tions of  its  sides,  which,  being  2-|  inches  wide,  give  abundant 
stability  to  the  carriage  in  training. 

Three  tie-bolts,  not  shown  in  the  figure,  placed  at  the  front, 
rear,  and  centre  of  the  slide,  connect  the  sides  and  prevent  lat- 
eral motion.  As  these  are  placed  low  down,  they  do  not  inter- 
fere with  the  movements  of  the  bed-plate,  C. 

These  carriages  are  considerably  lighter  than  the  wooden 
carriages  ; and  being  of  iron,  are  consequently  less  liable  to  injury 
from  exposure  in  service. 

989.  The  Howitzek  Field-caeeiage.  (Fig  234.) 


990.  The  Carriage  is  of  wrought-iron,  its  weight  being  re- 
duced to  the  least  limit,  about  500  lbs. ; the  axle,  has  cast  at 
its  centre  lugs  to  receive  the  loop  of  the  gun. 

991.  The  Trail,  B,  is  curved,  being  bolted  to  the  axle,  and 
supported  on  either  side  by  the  rod  braces,  C,  which  bolt  to  the 
trail  and  axle.  At  its  rear  end  the  trail  expands,  and  is  slotted 
for  the  trail-wheel,  E.  This  is  hung  on  a hollow  axle,  to  which 
is  attached  on  each  side  a guide  that  is  hinged  at  the  forward 
part  of  the  seat ; this  allows  the  trail-wheel  to  be  thrown  back 
on  the  trail  and  put  out  of  action.  A pin  chained  to  the  trail 
passes  through  it  and  the  hollow  axle.  With  the  wheel  in  the 
slot  and  confined  by  the  pin,  the  trail  of  the  carriage  rests  on  it, 
as  in  Fig.  234.  Beyond  the  slot  is  a socket  for  the  trail  hand- 
spike. 'The  elevator-box  is  like  that  in  the  boat-carriage. 

992.  The  Field  Carriage  ashore. — As  it  is  designed  to  oper- 
ate independently  of  a limber,  light  composition  frames,  having 
pins  projecting  upward,  are  attached  to  the  ti*ail  and  axle  on 


Nomenclature. 


B. — Trail. 

C.  — Trail-braces. 

D.  — Lags. 

H.  — Elevator-box. 


E.  — Trail- wheel . 

F.  — Socket. 

G.  — Elevator. 

K. — Ammunition  boxes. 


6TUT-CARRIAGES. 


355 


each  side,  on  which  the  ammunition  boxes  rest.  Their  bottoms 
are  fitted  with  metal  sockets  for  the  projecting  pins  of  the 
frames.  The  carriage  is  di’awn  by  means  of  a drag-rope  hooked 
to  a becket  near  the  sockets  ; this  rope  has  inserted  at  suitable 
intervals  wooden  handles  for  the  crew  to  hold.  At  the  hook  are 
two  shorter  ropes,  called  guide  ropes,  by  which  the  direction  of 
the  trail  is  governed  when  on  the  march.  To  the  axle  is 
hooked  a short  drag-rope,  which  is  used  as  a check,  or  holding- 
back  rope  in  steep  d^escents. 


Fig.  234. 


"When  in  action,  the  trail-pin  is  removed,  and  the  trail-wheel 
thrown  back  on  the  trail,  allowing  the  trail  to  rest  upon  the 
ground,  which  serves  to  check  the  recoil. 

993.  The  Field  Carriage  in  the  Boat  is  placed  aft  wdth  its 
trail  over  the  quarter  (Fig.  235),  so  as  not  to  impede  the  move- 
ments of  the  coxswain.  For  convenience  in  running  it  forward 
or  aft,  as  when  shifting  the  gun  from  the  boat  to  the  field-car- 
riage, or  the  reverse,  three  wooden  tracks  or  skids  are  laid  fore 
and  aft  on  the  thwarts,  and  bolted.  The  centre  being  for  the 
trail,  the  other  two  for  the  carriage-wheels. 

994:.  For  Landing  the  Field  Carriage^  short  skids  projecting 
ahead  to  the  beach  or  landing  are  provided  ; these  hook  to  the 
bows  of  the  boat,  and  are  braced  at  the  shore  end  by  a long 
iron  rod  and  hook  ; on  these  the  carriage- wheels  run. 

995.  Implements. — With  the  field  and  boat  carriage  are  sup- 
plied Eammer,  Sponge,  Ladle,  W orm^  and  Handspike ; two  of 


35G 


NAVAL  ORDNANCE  AND  GUNNERY. 


tliose  mentioned  being  on  the  same  handle,  one  at  each  end. 
The  latter  answering  a double  pui-poss,  first  as  a trail  hand- 
spike, and  second  as  a shifting-spar ; having  fitted  to  its  centre 


a metal  hook  used  in  the  groin et  around  the  neck  of  the  cascabel 
in  shifting,  mounting,  and  dismounting  the  Howitzer. 

Section  II. — English  If  aval  Gun-Carriages. 

996.  The  BKOADsmE  Scott  Cakkiage. 


Nomenclature. 


A.  — Bracket. 

B. — Bow  Compressor. 

C.  — Elevating  Gear. 

c. — Releasing  Lever  of  Elevat- 
ing Gear. 

D.  — Chain  Nipper  of  In-and- 

Out  Gear. 

E.  — Carriage  Wedges  of  Bow 

Compressor. 

b. — Eccentric  Lever  and  Gear. 

F. F. — Coned  and  Grooved  Rollers. 

G.  — Metal  Hook  for  lip  of  Front 

Track. 

H. H.H. ' — Raised  Metal  Tracks. 


K.  — Cogged  Training  Track. 

L.  — Preventer  Pivot  Bar. 

M.  — Slide  Wedges  of  Bow  Compressor. 

N.  — In-and-out  Gear. 

O.  — Endless  Chain. 

P. P. — Winches  of  Training  Gear. 

R — Shaft  of  Training  Gear. 

S.  — Training  MTieeL 
S'. — Cog-track. 

T.  — Shaft  Support. 

W. — Training  Brake. 

X- — Hydraulic  Jack. 

Y.  — Compressor  Pawl. 

Z. - — Buffer  Blocks. 


997.  The  Carriage  is  of  the  box  girder  description,  of 
mixed  wrought  and  cast  iron  (wrought  outside,  and  cast  inside). 


GUjST-CAEEIAGES. 


35T 


and,  unlike  tlie  old  pattern,  is  long  and  low,  thus  remedying  the 
rearing  back  tendency  of  short  and  high  carriages,  and  the  con- 
sequent downward  strain  on  the  deck  and  slide,  and  giving  a 


Fig.  236. 


much  greater  surface  to  absorb  the  concussion  or  shock  of  re- 
coil. As  the  carriage  is  made  so  much  lower,  the  slide  is  corre- 
spondingly raised,  thus  maintaining  the  same  heiglit  of  the  axis 
of  the  trunnion  above  the  deck,  and 
allowing  room  for  tlie  cogged  gear 
beneath  the  slide. 

998.  The  Slide  is  of  girder 
wrought-iron,  filled  in  on  each  side 
with  teak  (see  Fig.  239),  with  no  head- 
plate,  thus  allowing  the  gun  to  be 
run  farther  out  and  facilitating  point- 


The  upper  surface  of  the  slide 
is  an  inclined  plane,  having  an  angle 
of  from  3°  to  5°  for  ordinary  broad- 
side guns,  which  serves  to  check  the 
recoil,  and  facilitates  the  running  out 
of  the  gun. 

999.  The  Dech  (Fig.  237)  beneath 
the  slide  has  bolted  to  it  four  (4) 
metal  tracks,  H,  H,  II',  and  K ; the 
first  two,  H,  are  usually  solid,  and 
have  cast  on  them  upper  surface  a rib 
to  take  the  groove  of  the  slide-rollers 
F.  These  tracks  are  raised  at  their 
extremities,  to  allow  for  the  deck  curv- 
ature, and  thus  prevent  alteration  of 
the  sights  in  extreme  training.  The 
track,  K,  is  cogged  fo)’  the  cog-training 
wheel,  and  may  be  of  brass  or  iron, 
usually  the  former.  The  track  H'  is  of  metal,  having  cast  on 
its  forward  side  a strong  projecting  lip,  under  which  the  metal 


hook,  G,  attached  to  the  slide,  takes. 


NAVAL  ORDNANCE  AND  GUNNERY. 


358 


1000.  The  Pivot  (Fig.  238)  is  independent  of  the  ship’s 
side  and  any  accident  that  might  occur  to  it,  as -the  recoil  is 
received  from  the  coned  and  grooved  rollers,  F,  of  the  slide, 


Fig.  338. 


and  the  metal  hook,  G,  by  the  three  metal  tracks,  H.  Were  the 
shock  received  by  a pivot  at  the  side,  a heavy  shot  impinging 
there  might  and  probably  would  prevent  the  further  service  of 
the  gun. 

1001.  The  Dimensions  of  a 12-inch  25-ton  Broadside  Gun- 
carriage  are  as  follows : Length  of  slide,  15  ft.  6 in. ; width,  6 
ft. ; length  of  carriage,  8 ft.  9 in. ; height  of  trunnion  above 
the  deck,  5 ft.  1^  in.,  the  relative  length  of  slide  and  carriage 
permitting  a recoil  of  6 feet. 


Fig.  239. — Section  at  Compressor. 


Fig.  340. — Rear  view  of 
Carriage. 


Fig.  241. — ^Rear  view  of  Slide. 


Fig.  243. — Front  view  of  Slide. 


GUN-CAKRIAGES. 


359 


For  other  guns  the  dimensions  are  similarly  proportioned. 

1002.  TliJi  Self-Acting  Bow  Compressor^  B,  consists  of 
strong  metal  bows  hung  by  their  centi-es  through  a hole  in 
each  side  bracket.  (See  Fig.  24:6,  B.)  From  the  carriage  short 
wedge-shaped  plates,  E,  are  suspended  between  hard  wooden 
haulks,  and  wedge-shaped  iron  plates  fixed  to  the  girders  of  the 
slide  M.  A wheel  with  screw  attached  works  through  the 
outer  end  of  the  metal  bow,  setting  the  plates  firmly  together 
(Fig.  239).  The  circumference  of  the  wheel  is  notched  to  re- 
ceive pawl,  Y,  attached  to  the  bow  at  the  height  of  the  wheel. 
The  weight  of  the  gun,  when  let  down  from  its  eccentric 
rollers,  drives  the  up])er  wedge,  E,  tight  between  the  lower 
ones,  M,  and^the  downward  concussion  of  firing  tends  to  drive 
them  still  more  together,  while  the  action  of  lifting  the  gun- 
carriage  on  its  eccentric  rollers,  to  run  it  out,  releases  the 
wedges  because  of  their  shape. 

1003.  The  Elevating  Gear,  C (Fig.  238),  consists  of  a 
cogged  arc  attached  to  the  side  of  the  breech  of  the  gun,  acted 
on  by  a cog-wheel  inside,  and  drum  outside  the  bracket,  and 
fixed  to  the  same  pinion.  Through  it,  sockets  are  pierced  in  the 
periphery  of  the  drum,  into  which  pointed  handspikes  are 
placed  in  elevating  or  depressing  the  gun — a clamp  outside 
the  drum  nipping  it  at  the  desired  elevation ; a holding-pin 
attached  to  the  bracket  assists  the  clamp. 

1004:.  The  Eccentric  Gear,  h (Fig.  238),  consists  of  a shaft 
across  the  rear  end  of  the  carriage,  car- 
rying the  eccentric  rollers,  placed  in  the 
under  and  rear  side  of  the  brackets.  A 
cog-wheel  on  the  inside,  worked  by 
levers  on  the  outside,  acts  on  a V -shaped 
cog  when  on  the  eccentric  axle,  throw- 
ing the  eccentric  rollers  in  and  out  of 
action.  A pawl,  or  releasing  lever  (Fig. 
238),  is  provided  for  holding  the  eccen- 
tric in  action.  The  latest  carriages  have 
their  eccentric  rollers  worked  by  an  hy- 
draulic jack,  X,  on  one  side,  and  cog- 
wheels and  drum  on  the  other  (Fig. 
24:3) ; with  the  jack  the  heaviest  gun  may  be  easily  lifted  by 
one  man. 

1005.  The  In-and-Out  Gear  (X,  Fig.  237). —The  carriage, 
being  lifted  oiit  on  its  rear  eccentrics  as  before  described,  is 
run  in  and  out  by  means  of  spur  wheels  and  pinions  fixed  to 
the  rear  end  of  the  slide  on  each  side,  worked  by  Avinch-han- 
dles,  which  drive  a shaft  across  the  rear  end  of  the  slide.  Two 


Fig.  243. 


360 


NAVAL  OEDNANCE  AND  GTLNNTEET. 


endless  chains,  O,  run  around  spockePioheels  fitted  to  this  shaft, 
and  the  forward  end  of  the  slide  (that  foi*ward  having  an 
elastic  shackle)  by  which  the  chain  is  kept  taut  at  all  times, 
the  upper  part  of  tlae  chain  passing  through  holes  in  the  car- 
riage, When  not  in  use,  the  chains  are  not  attached  to  the 


carriage  ; but  when  required,  the  upper  part  of  each  chain,  0, 
is  caught  by  an  arrangement  called  the  chain-dipper.  (See  hig. 
244,  D.)  This  consists  of  an  eccentric  in  the  bottom  of  the 
carriage,  worked  by  a lever,  by  which  the  eccentric  catches  the 
chain  in  the  teeth  fitted  to  the  upper  side  of  the  box  in  the 
bottom  of  the  carriage,  and  through  which  the  chain  passes. 
When  the  In-and-Out  Gear  is  moved  with  the  chain  caught,  it 
cari-ies  the  carriage  with  it,  either  in  or  out.  By  throwing  the 
lever  up,  the  chain  is  released,  and  the  carriage  ceases  to  move. 

Buffer  Blochs,  2i  (Fig.  237),  of  india  rubber  are  placed  at 
each  end  of  the  slide  to  receive  the  carriage  should  it  move  out 


with  tackles  should  occasion  require  it. 

1006.  The  Training  Gear,  li,  S,  T,  W,  (Figs.  238,  241,  245), 


GUN’-CAIIRIAGES. 


361 


consists  of  a crown-wheel  and  bevel  pinions,  taxed  to  the  rear 
end  of  the  slide,  woi’ked  by  winch-handles,  which  drive  a shaft, 
R,  extending  forward  beneath  the  slide,  and  armed  at  its  for- 
ward end  with  a cog-wheel,  woi’king  in  the  cogged  ti’ack,  K, 
on  the  deck. 

For  Extreme  Train,  when  the  vessel  is  rolling  deep,  or  at 
any  time  that  additional  power  is  reqnii-ed,  a second  driving- 
pinion  is  provided,  giving  twice  and  a half  the  power  of  the 
single  pinion  ; a pawl,  to  lock  the  training-geai’,  when  the  gnn 
is  stationai-y,  and  a bi’ake,  W,  to  control  the  rapidity  of  train- 
iiag.  The  latter  consists  of  a dimiiuitive  bow  compressor 
applied  to  the  training-geai*,  near  the  winch-handle  (Fig.  21-5, 
W).  Eye-bolts  for  trahaing  are  fitted  to  the  slide  to  be  used 
with  tackles. 

1007.  Advantages  of  Mechanical  Caueiages. — The  shocJc 
of  recoil  is  I’eceived  by  metal  ribs  cast  on  tlie  npjaer  surface  of 
the  heavy  solid  metal  tracks,  H,  and  by  a sti’ong  metal  hook, 
G,  attached  to  the  front  end  of  the  slide,  whicli  ties  it  down 
to  the  deck  by  the  hook,  taking  under  the  strong  metal  lip  of 
the  front  ti’ack,  H'.  By  this  means  the  shock  of  recoil  is  not 
received  at  any  single  point,  but  is  distributed  over  the  sui’face 
of  the  three  tracks,  and  thence  to  the  deck,  and  thus  the  tear- 
ing or  rending  effect  is  much  less  at  any  one  of  these  points 
than  it  would  be  on  a single  pivot-bolt.  Again,  the  compressor 
wedges,  E and  M,  are  not  only  wedge-shaped  vertically,  but  are 
slightly  so  longitudinally,  by  which  arrangement  the  I'ecoil  is 
gradually  checked  or  absoi’bed,  instead  of  being  suddenly  re- 
sisted as  with  ordinai’Y  compressors. 

1008.  The  Bow  Compressor,  B,  is  self  acting,  fi’om  its  pecu- 
liar construction.  The  compi’essoi’-plates  being  wedge-shaped 
both  vertically  and  horizontally, 
lifting  the  carriage  must  nec- 
essarily ease  them  ; lowei’ing  the 
carriage,  the  reverse  occurs. 

Therefore  the  wheel  being  set  to 
a point  (determined  by  practice) 
and  pawled,  the  mere  running 
out  of  the  gun,  in  one  case,  and 
firing  in  the  othei’,  operates  the 
compressor.  So  that  the  com- 
pression by  the  wheel  having 
once  been  determined,  the  gam 
may  be  fii-ed  a long  time  with- 
out the  compression  being  altered. 

Experiments  prove  that  one  man  may  set  the  wheel  so  taut 


362 


NAVAL  ORDNANCE  AND  GUNNERY. 


as  to  reduce  the  recoil  to  3 feet,  one  half  that  allowed  by  the 
slide.  By  this  arrangement  the  danger  occurring  with  most 
compressors,  viz.,  that  the  compressor-man  will  set  the  com- 
pressor too  taut  or  not  enough,  is  entirely  obviated  ; and  any 
compressor  not  self-acting  is  liable  to  be  worked  so,  and  the  gun 
and  carriage  seriously  injured  thereby. 

1009  Training  Gear. — As  this  gear  is  attached  to  the  rear 
end  of  the  slide,  it  is  much  less  exposed  to  an  enemy’s  shot 
than  at  the  ship’s  side,  or  in  any  other  position  about  the  slide. 
And  at  night,  or  when  smoke  and  noise  would  liinder  the  men 
at  the  side  of  a gun  worked  by  tackles  from  seeing  or  hearing 
their  gun-captain,  the  captain  of  a gun,  fitted  with  mechanical 
training  gear,  regulates  the  movements  of  the  slide  with  the 
greatest  ease,  as  the  motive  power,  viz.,  the  men  at  the  winch- 
handles,  are  within  a few  feet  of  him.  Again  this  position  of 
the  motive  power  enables  him  to  train  and  keep  his  gun  on 
the  object  as  it  is  being  run  out,  and  save  much  valuable  time, 
especially  in  firing  at  a moving  object.  In  practice  the  con- 
trolling brake,  W,  has  answered  its  purpose  very  well,  and  the 
training  gear  greatly  increases  the  rate  of  firing  under  any 
conditions,  its  advantages  being  best  shown  in  bad  weather. 
AVith  it  and  the  in-and-out  gear,  much  manual  labor  is  saved, 
the  crew  being  reduced  thereby  to  one-third.  In  training  guns 
by  tackles  and  handspikes,  the  motion  is  verjmrregular,  the  guns 
being  many  times  jumped  beyond  the  desired  point,  while  with 
the  Mechanical  Gear  the  greatest  nicety  is  obtained. 

1010.  High  and  Low  Carriages. — The  effect  of  reducing 
the  height  and  increasing  the  length  of  carriages  may  be  il- 
lustrated by  assuming  an  extreme  case.  Imagine  a very  high 
and  short  carriage  on  one  slide,  and  a very  long  and  low  car- 
riage on  another.  The  gun  being  fired  horizontally,  the 
shock  of  recoil  in  the  first  instance  will  be  communicated  by  a 
lever,  represented  by  the  vertical  height  and  length  of  the  car- 
riage, and  the  leverage  being  great,  the  shock  will  be  more 
powerful,  while  with  the  long,  low  carriages  the  leverage  is 
much  reduced,  and  consecpiently  the  shock  on  the  slide,  and  a 
longer  surface  is  provided  for  absorbing  the  recoil.  Hence 
the  same  decks  will  sustain  the  firing  of  heavier  guns  by  the 
use  of  long,  low  carriages  and  high  slides,  preserving  the  axis 
of  the  gun  at  the  same  height  above  the  deck. 

1011.  The  Didpkessiox  Cakeiages  (Fig.  21T). — These  were 
designed  by  Capt.  Scott,  11.  JS[.,  for  the  smaller  upper  guns  of 
Broadside  vessels,  as  an  auxiliary  defence  against  Torpedo  or  at- 
tacking boats  very  near  or  alongside  the  vessel,  as  at  such  times 
the  main-deck  guns  do  not  possess  sufficient  depression  to  protect 


GTJN-CAERTAGE9. 


363 


her  against  them.  Referring  to  Fig,  2i7,  the  slide,  A,  is  of  iron 
and  has  an  inclination  of  10°  to  the  front.  To  the  slide  is  at- 


Fiq.  247. 


tached  the  cylinder  of  an  hydraulic  compressor,  B,  the  piston 
being  fixed  to  the  front  end  of  the  carriage,  which  is  of  iron;  an 
elevating  arc,  0,  attached  to  the  gun  and  worked  by  a pinion  and 
wheel  instead  of  the  drum  and  handspikes  in  use  with  heavy  guns, 
permits  of  20°  elevation  and  30°  depression.  A clamp  fitted  to 
the  axle  fixes  the  gun  as  desired.  Tlius  with  the  ship  on  an  even 
keel,  projectiles  may  be  thrown  100  ft.  high,  at  100  yards’  dis- 
tance, or  into  a boat  as  near  as  13  yards  from  the  ship’s  side. 
The  great  amount  of  depression  obtained  makes  them  a very  use- 
ful addition  to  Broadside  Iron-clad  armament,  as  with  the  ut- 
most depression  obtainable  with  the  Broadside  carnages,  the 
shot  would  fall  over  twice  as  far  from  the  ship’s  side.  Without 
these  depression  carriages,  there  would  be  left  around  the  ves- 
sel a free  zone  of  fire  of  considerable  size,  in  which  attacking 


364 


NAVAL  ORDNANCE  AND  GUNNERY. 


boats  might  lie  with  perfect  immunity  from  the  vessel’s  hea’^y 
guns. 

1012.  The  Eng- 
lish Tueeet  Cae- 
EiAGE.  (Figs.  248, 
249.) 

The  Slide  con- 
sists of  four  wrought- 
iron  girder  beams,  A, 


built  into  the  Turret 
below  the  deck  (see 
Fig.  248),  consti- 
tuting strengthening 
struts,  and  forming 
a part  of  the  ship. 
These  fixed  girders 
have  an  inclination  of 
about  3°,  and  form 
slides  on  which  are 
mounted  two  com- 
pound pivoting  gnn- 
carriages,  the  train- 
ing being  effected  by 
the  revolution  of  the 
Turret  itself. 

The  only  point  of 
piinciple  in  which 
the  Turi-et  differ 
from  the  Broadside 
carriages,  is  in  their 
possessing  compound 

vertical  pivoting  gear,  to  minimize  the  vertical  area  of  the  port. 
To  accomplish  this,  the  carriage  and  slide  with  tlie  gun  were 
lifted  bodily  to  set  heights  by  means  of  screws  working  irregu- 
larly, involving  considerable  loss  of  time.  It  is  now  obtained  by 
lifting  the  gun  only.  This  is  effected  by  supporting  the  gun  in 
wrought-iron  blocks,  susceptible  of  vertical  motion  in  the 
brackets.  These  blocks  are  united  beneath  the  gun  by  a curved 
transom  acted  on  beneath  its  centre  by  the  ram  of  an  hydraulic 
jack  attached  to  the  bottom  plate  of  the  carriage,  which  raises 
the  gun  bodily  about  6 inches  per  minute.  Iron  props  of 
different  lengths  are  used  to  support  the  trunnion-blocks  in  the 
different  positions  in  which  it  is  intended  to  fire. 

1013.  Elevation. — On  each  step  the  elevation  and  depres- 
sion is  regulated  by  elevating  gear,  differing  from  the  Broad- 


Gim-CAERIAGES. 


365 


side  gear,  in  that  it  is  adapted  to  use  with  the  axis  of  the  gun 
at  the  three  different  heights ; a single  man  at  the  eascabel  of 
the  gun  works  the  pinion  and  spur-wheel,  which  raise  or  lower 
the  gun  along  the  cogged  arc,  or  elevating-bar.  The  steps  are 
so  arranged  that  the  upper  gives  no  elevation  and  7°  depres- 
sion, the  bottom  step  15°  elevation  and.  no  depression  ; the 
middle  or  ordinary  fighting  step  gives  9°  elevation  and  2°  de- 
pression. This  division  of  step  may  be  changed  at  any  time, 
by  substituting  iron  props  of  other  heights. 

1014.  The  Carriages  are  adapted  to  the  circular  form  of 
the  tiu’ret  by  lengthening  the  minor  bi’acket  of  each,  and  both 
are  so  reduced  in  front  as  to  leave  considerable  space  betw^een 
them  and  the  turret,  thus  rendering  them,  like  the  broadside  car- 
riage, independent  of  concussions  or  indentations  of  the  armor*. 

1015.  Recoil. — The  shock  of  recoil  on  the  trunnion-blocks 
is  distributed  over  large  bracket  sirr-faces  by  the  wrought -iron 
guides  in  w’hich  they  move.  That  from  the  carriage  is  conveyed 
to  the  girders  by  the  long  brackets  of  the  carriage,  whose  inner 
plate  of  cast-iron  resting  on  the  girders  form  excellent  frictional 
surfaces. 

1016.  The  Turret  has  a spindle  at  its  bottom  extending 
downward  a short  distance  into  a strong  framework  built  for  it ; 
the  lower  edge  of  the  turret  rests  on  coned  rollers,  connected  by 
rods  with  a tiange  or  collar  on  the  spindle.  The  whole  being 
protected  by  a shield  (Fig.  218).  It  is  revolved  by  machinery 
worked  by  steam  or  by  hand  power ; usually  both  are  provided. 
If  worked  by  hand,  the  handles  by  which  the  power  is  applied 
are  placed  on  the  deck  below,  outside  the  turret,  requiring  with 
eighteen  men  about  eighty  seconds  to  perform  one-half  revolu- 
tion ; with  steam,  eighteen  seconds. 

1017.  The  In-and-Out  Gear  consists  of  a shaft  canying  two 
endless  chains,  connected  and  detached  from  the  carriage  in  the 
same  way  as  with  the  Broadside  carriage.  The  shaft  extends 
through  the  iron  girders  and  the  sides  of  the  turret,  to  which 
handles  are  fixed  to  be  worked  by  the  men  outside.  It  is 
arranged  in  halves  and  connected  by  a coupling,  so  that  each 
gun  may  or  may  not  be  worked  separately.  As  nearly  twice 
the  power  is  required  to  run  in  and  out  a Turret  gun  as  a 
Broadside,  the  gearing  is  arranged  to  multiply  the  manual 
labor  to  the  desired  extent,  with  the  Turret  one  hundred  and 
fifty  times  and  Broadside  ninety. 

Elastic  Buffers  are  placed  at  each  end  of  the  girders  or 
slide,  to  check  the  gun  should  it  go  in  or  out  violently. 

1018.  Pointing  is  efiected  by  sights  on  top  of  the  turret,  on 
which  allowance  is  made  for  the  heio-ht  abov*e  the  sun.  Inaceu- 

O O 


SG6 


NAVAL  ORDNANCE  AND  GUNNERY, 


racies  in  the  parallelism  of  the  sights  and  axis  of  the  gnn  are  so 
far  compensated  for  hy  the  greater  distance  between  the  front 


and  rear  sight  (Turret),  that  with  rolling  motion,  better  shooting 
is  sometimes  made  than  with  the  short  radius  sights  on  the  gun 
itself.  By  reference  to  the  figure,  it  will  he  seen  that  the  same 
compressor  and  in-and-out  gear  are  used  with  both  Turret 
and  Broadside  carriages.  When  the  Turret  is  fixed  and  the  gun 
movable,  the  latter  rests  on  a turn-table  worked  by  steam,  which 
brings  the  gun  to  the  port,  the  training  being  effected  by  the 
mechanical  gear. 

1019,  The  Theket  Indicatoe. — With  Turret  guns,  extreme 
depression  can  only  be  given  when  aiming  directly  abeam,  and 
as  the  gun  is  pointed  forward  or  abaft  the  beam,  a correspond- 
ing reduction  of  the  extreme  beam  depression  occurs.  Tliere  is 
also  great  liability  of  firing  through  the  decks  or  shooting  away 
ngging,  etc.  To  obviate  this  danger  and  enable  the  person 


Gim-CAERIAGES. 


367 


pointing  tlie  gun,  either  on  top  or  in  the  turret,  to  point  the  gun 
at  night  or  in  the  day-time,  clear  of  the  deck  and  all  obstruc- 


ELEVATION  OF  INDICj 


IN  DAVUCKT 


SEEN 


Fig.  250. 


tions,  an  instrument  has  been  devised  called  the  TuiTet  Indicator, 
(Fig.  250),  fixed  either  on  the  turret  or  in  it.  By  which  is  seen 
at  a glance,  by  day  or  night,  the  angle  of  depression  at  which 
both'or  either  of  the  guns  can  be  fired  at  every  bearing,  clear  of 
the  deck  and  all  obstructions. 

1020.  Eeferring  to  Fig.  250,  it  will  be  seen  that  the  indica- 
tor consists  of  a hollow  disk,  with  a rod  through  its  centre  carry- 
ing a pointer ; it  is  graduated  near  its  outer  circumference  to 


368 


NAVAL  ORDNANCE  AND  GUNNERY. 


indicate  the  arc  of  train  that  the  gun  makes  with  the  beam.  The 
number  of  degrees  marked  on  the  inner  circle,  as  seen  by  day- 
light, indicate  the  amount  of  safe  depression  which  maybe  given 
at  that  arc  of  train,  the  gun  right  or  left  being  marked  on  the 
disk ; also  the  fore  and  aft  and  beam  points,  the  black  spaces  in- 
dicating the  obstructions  to  fire. 

1021.  For  use  at  nighty  the  clear  space  of  the  disk  as  seen 
by  daylight  is  illuminated,  by  which,  although  it  appears  blank 
by  day,  at  night  it  shows  the  same  graduated  arc  of  train  and 
corresponding  amount  of  depression  as  the  outer  disk,  the  fore 
and  aft  points  being  indicated  by  illuminated  letters  seen  through 
the  open  space  in  the  upright  piece.  By  machinery  or  hand 
power  the  pointer  is  made  to  follow  the  movements  of  the  Tur- 
ret, recording  the  arc  of  train  and  correspondino:  depression. 

1022.  THE  MONCEIEFF  SYSTEM  O'E  GUX-CAE- 
EIAGE. — The  principle  on  which  this  carnage  is  constructed 
may  be  shortly  stated  as  that  of  utilizing  the  force  of  the  recoil 
in  ordei’  to  lower  the  whole  gun,  so  that  it  can  be  loaded  out  of 
sight  and  out  of  exposure,  while  retaining  enough  of  that  force 
to  bring  the  gun  up  again  into  the  bring  position. 

This  principle  belongs  to  all  the  carriages  ; but  the  forms  of 
these  carriages,  as  well  as  the  method  in  which  this  principle  is 
applied,  vary  in  each  case.  For  instance,  in  siege  guns,  where 
weight  is  an  element  of  importance,  the  recoil  is  not  met  by 
counterpoise.  With  heavy  garrison  gims,  on  the  other  hand, 
which  wdien  once  mounted  remain  permanent  in  their  positions, 
there  is  no  objection  to  weight.  In  that  case,  therefore,  the 
force  of  gravity  is  used  to  stop  the  recoil,  because  it  is  a foi’ce 
always  the  same,  easily  managed,  and  not  likely  to  go  wrong. 

The  great  difficulty  arising  from  the  enormous  destructive 
force  of  the  recoil  of  heavy  guns  is  here  overcome. 

1023.  That  part  of  the  carriage,  E (Fig.  251),  which  is  called 
the  elevator,  may  be  spoken  of  and  treated  as  a lever;  this  lever 
has  the  gun-carriage  axle  at  the  end  of  the  power-arm,  and  the 
centre  of  gravity  of  the  counter-weight,  C,  at  the  end  of  the 
weight-arm,  there  being  between  them  a moving  fulcrum. 

When  the  gun,  G,  is  in  the  firing  position,  the  fulcrum  on 
which  this  lever  rests  is  almost  coincident  with  the  centre  of 
gravity  of  the  counter-weight,  C,  and  when  the  gun  is  fired  the 
elevators  roll  on  the  platform  and  consecprently  the  fulcrum,  or 
point  of  support,  travels  away  from  the  end  of  the  weight-arm 
towards  the  end  of  the  power-arm,  or  in  other  words,  it  passes 
from  the  counter-weight,  C,  towards  the  gun,  G. 

When  the  gun  is  Fred,  its  axle  passes  backwards  on  the  up- 
per or  fiat  part  of  a cycloid.  It  is  free  to  recoil,  and  no  strain 


GUN-CAEEIAGES. 


369 


is  put  upon  any  part  of  the  structure,  because  the  counter- 
weight commences  its  motions  at  a very  low  velocity.  As  the 


recoil  goes  on,  however,  the  case  changes  completely,  for  the 
moving  fulcrum  travels  towards  the  gun,  making  the  weight- 
arm  longer  and  longer  every  inch  it  travels.  Thus  the  resist- 
ance to  the  recoil,  least  at  lirst,  goes  on  in  an  increasing  pro- 
gression as  the  gun  descends,  and  at  the  end  of  the  recoil  it  is 
seized  by  a self-acting  pawl,  or  clutch. 

The  recoil  takes  place  without  any  jar,  without  any  sudden 
strain,  and  its  force  is  retained  under  control  by  the  men  at  the 
gun,  to  bring  it  to  the  tiring  position  at  any  moment  they  may 
choose  to  release  it.  The  recoil,  moreover,  however  violent  at 
first,  does  not  put  injurious  horizontal  strain  on  the  platform. 

1024.  Hydkaulic  Appliances. — The  hydraulic  system  of 


Fig.  252.  — Turret  with  two  38-ton  guns,  showing  loading  from  below  under 
port,  and  hydraulic  buffer. 


loading  and  working  guns  as  applied  to  the  turret  of  the 
Thunderer^  is  illustrated  by  Fig.  252. 

24 


370 


NAVAL  OEDNANCE  AND  GUNNEET. 


The  principal  mechanism  of  a gun-camage  monnted  on  a 
slide  is  that  for  absorbing  and  regulating  the  force  of  recoil, 
and  for  moving  the  gun  from  loading  to  firing  position,  or 
back.  In  the  usual  English  type  of  carriage  the  former  office 
is  performed  by  a peculiar  and  very  powerful  brake,  known  as 
the  compressor,  and  the  latter  usually  by  winch-gear,  giving 
motion  to  an  endless  chain  so  placed  beneath  the  carriage  that 
it  may  be  seized  at  any  point  by  a clutch  on  the  carriage. 

1025.  In  the  hydraulic  arrangement  all  this  mechanism  is 
replaced  by  the  press  or  cylinder  seen  in  the  figure ; this  press 
acts  both  to  check  recoil  and  to  give  motion  to  the  gun-carriage 
on  the  slide.  It  is  fixed  on  the  slide  in  the  line  of  recoil,  with 
its  piston-rod  permanently  attached  to  the  carriage. 

1026.  Running  In  or  Out. — To  run  the  carriage  in  or  out 
it  is  only  necessary  to  admit  to  one  side  or  other  of  the  piston 
the  water  delivered  from  the  steam-pumps.  When  the  gun 
recoils  the  w^ater  is  di-iven  out  of  the  press  through  a loaded 
and  partly  balanced  valve,  the  resistance  of  which  to  its  passage 
arrests  the  recoil,  and  can  be  adjusted  at  a moment’s  notice,  so 
as  to  regulate  the  extent  of  recoil  under  different  conditions. 
In  its  office  of  checking  recoil  it  is  self-acting,  and  always  ready 
for  use  without  any  preparation.  Whatever  the  weight  of  the 
gun,  no  men  are  required  for  running  in  or  out  beyond  the  one 
whose  duty  it  is  to  open  and  close  the  valves  which  allow  the 
water-pressure  to  act. 

1027.  The  gun  is  made  partial  muzzle-pivoting  by  hinging 
the  slide  horizontally  at  the  rear,  the  front  end  being  free  to  be 
raised  or  lowered  upon  suitable  chocks  from  the  floor  of  the  tur- 
ret, at  the  different  heights  required  to  give  the  desired  range 
of  elevation  to  the  gun  in  the  port. 

1028.  Loading. — The  loading  is  effected  by  turning  the 
turret  so  as  to  bring  the  muzzle  of  the  gun  opposite  either  one 
of  two  distinct  sets  of  loading-gear  placed  on  the  main  deck, 
and  locking  it  in  this  position  by  a catch.  The  gun  is  at  the 
same  time  depressed,  so  that  the  charge  may  be  raised  to  the 
muzzle  and  pushed  home  in  the  bore  at  an  inclination  from 
below  the  upper  deck. 

The  projectile  is  brought  up  to  the  loading-place  on  a small 
railway-truck  controlled  by  a friction-plate,  which  clamps  it  to 
the  rails  whene^•er  the  truck-handle  is  lowered.  It  is  then  run 
on  to  a hoist  which  rises  with  it  out  of  the  main  deck  until 
arrested  by  stops  placed  so  as  to  bring  the  hoist  to  rest  when 
the  projectile  is  in  line  with  the  bore  of  the  gun.  It  is  then 
pushed  off  the  truck  into  the  muzzle,  and  raimned  home  by  an 


GUN-CAEEIAGES.  371 

hydraulic  rammer,  consisting  of  a parallel  tube  in  which  runs  a 
piston-rod  armed  with  a rammer-head. 

1029.  Sjponging. — The  same  rammer  is  used  for  pushing 
home  the  charge  and  also  for  cleaning  the  bore  after  each 
round.  For  this  purpose  the  head  of  the  rammer  is  formed 
like  an  ordinary  sponge,  and  it  contains  a self-acting  valve, 
which  opens  when  pushed  against  the  end  of  the  bore,  so  as  to 
discharge  a strong  jet  of  water  within  the  gun.  In  loading,  this 
valve  does  not  act,  because  it  does  not  then  come  in  contact, 
owing  to  the  peculiar  form  of  the  rammer-head. 

The  same  form  of  rammer  has  been  made  telescopic  to  re- 
duce its  length.  A wad  pushed  home  with  the  projectile  pre- 
vents it  from  running  forward  when  the  rammer  is  withdrawn. 

1030.  Advantages. — The  advantages  claimed  for  this  method 
are ; 

1.  The  loading  operation  is  transferred  from  a confined 
space  and  exposed  position  in  the  port,  to  a roomy  and  conve- 
nient place  on  the  main  deck,  where  the  apparatus  is  completely 
protected. 

2.  The  dimensions,  and  consequently  the  weight,  of  the  tur- 
ret required  to  protect  any  given  gun  are  greatly  reduced,  be- 
cause the  minimum  diameter  that  will  take  m the  length  of  the 
gun  is  all  that  is  necessary,  without  additional  space  for  loading. 

3.  Instead  of  a large  gun’s  crew,  one  man  in  the  turret  and 
one  outside  may  direct  and  control  all  the  movements  of  the 
heaviest  gun,  and  may  load  and  fire  it  wfithout  other  help  than 
that  involved  in  bringing  up  the  ammunition  ; and,  finally,  far 
greater  rapidity  of  fire  is  obtained  than  would  be  possible  by 
manual  power. 

The  loading  positions  are  duplicated,  to  give  a reserve  in 
case  of  accident,  or  to  enable  that  one  to  be  selected  which  may 
best  keep  the  turret-port  out  of  the  line  of  the  enemy’s  fire. 
In  the  event  of  accident  to  the  hydraulic  loading-gear,  the  gun 
may  be  loaded  from  below  by  hand. 

The  carriages  are  arranged  so  that  recourse  may  be  had 
to  hand-power  for  working  the  guns,  should  any  accident  to, 
or  failure  of,  the  hydraulic  system  occur.  For  this  purpose 
the  mechanical  means  of  working  by  hand  have  been  retained 
side  by  side  with  the  hydraulic  apparatus,  and  it  has  been  nec- 
essary to  adhere  generally  to  the  usual  mode  of  mounting  a 
gun.  But  it  is  thought  that  w'here  this  condition  is  not  im- 
posed, great  advantages  in  simplicity  and  strength  of  the  appa- 
ratus required,  and  in  the  safety  with  which  exceptionally 
heavy  guns  may  be  worked,  can  be  obtained  by  a radical  change 
in  the  method  of  mounting  the  gun. 


CHAPTEE  YIIL 


EXPLOSIVE  AGENTS. 

Section  I. — General  Consideration  of  Explosives.^ 

1031.  Definitions. — An  explosion  may  be  considered  as  the 
result  of  a chemical  change  in  the  solid  or  liquid  body,  by 
which  is  suddenly,  or  very  rapidly,  produced  from  it  a gi’eat 
volume  of  highly  expanded  gas. 

Explosives  may  be  defined  as  a class  of  bodies,  the  mole- 
cules of  which  are  in  such  a state  of  unstable  equilibrium,  that 
a slight  disturbing  agency  will  cause  chemical  change  among 
them  ; the  effect  of  which  change  is  to  produce  suddenly  a very 
large  volume  of  highly  expanded  gas. 

1032.  Explosive  Effect. — Explosive  reaction  is  the  tei-m 
applied  to  the  chemical  change  which  takes  place  in  explosive 
bodies  when  their  equilibrium  is  destroyed,  while  the  blow  or 
impulse  given  by  the  sudden  production  of  the  large  volume  of 
highly  heated  gas  is  termed  explosive  effect. 

KJ33.  Explosive  Compounds. — An  explosive  compound  is  a 
single  definite  chemical  compound,  the  particles  of  which  re- 
arrange themselves  to  form  the  gases  evolved  by  explosion. 

The  more  important  of  the  explosive  compounds  in  exten- 
sive use  for  '\  arious  purposes  are  : 

Eulminate  of  Mercury 
Evlminate  of  Silver, 

Nitro-glycerine, 

Gun-cotton. 

Explosive  compounds  are  much  more  sudden  and  violent 
ill  their  action  than  explosive  mixtures. 

1031.  Explosive  Mixtuees. — An  explosive  mixture  consists 
of  combustibles  and  supporters  of  combustion,  mixed  so  that 
by  their  mutual  action  a large  quantity  of  gas  is  developed. 
The  most  important  ex]ilosive  mixture  is  gunpowder. 

1035.  The  combustible  bodies  that  maj’  be  used  are  very 
numerous,  but  practically  there  are  only  two  bodies  which  are 
used  to  supply  the  oxygen  necessary  for  burning  the  combusti- 

* Extracts  from  Lectures  of  Prof . TF.  H.  Hill,  IF.  S.  Torpedo  Station. 


EXPLOSIVE  AGENTS. 


373 


ble.  These  are  potassium  nitrate  or  saltpetre,  and  potassium, 
chlorate.  Therefore  all  mixtures  may  be  divided  into  two 
classes,  namely : nitrate  and  chlorate  mixtures. 

Nitrate  Mixtures. — The  most  important  one  under  tliis 
head  is  that  composed  of  saltpetre,  sulphur,  and  charcoal  (Art. 
lOdT).  Ill  various  proportions  this  mixture  is  employed  for 
very  many  purposes ; the  action  is  the  same  in  all  cases,  so  that 
the  explosion  of  gunpowder  fully  illustrates  them  all.  Nitra  e 
mixtures  are  not  greatly  susceptible  to  friction,  concussion,  or 
percussion.  In  general  the  explosion  of  these  mixtures  is  com- 
paratively slow. 

1036.  Chlorate  Mixtures. — In  general,  the  explosion  of 
these  mixtures  is  much  more  sudden  and  violent  than  that  of 
nitrate  mixtures,  and  they  are  also  much  more  sensitive  to  per- 
cussion, concussion,  and  friction.  Glenerally  speaking,  all  chlor- 
ate mixtures  are  unsafe,  and  dangerous  to  handle  or  transport 
on  account  of  their  susceptibility  to  accidental  explosion. 

1037.  As  examples  of  this  class  may  be  mentioned,  potas- 
sium chlorate  mixed  with  resin,  galls,  gambia,  tan, .etc. ; such  as 
Hosley’s,  Oriental,  Erhardt’rs  powders,  etc. ; with  sugar,  potas- 
sium ferrocyanide,  or  ferricyanide ; such  as  white  or  German 
gunpowder ; with  sulphur  as  used  in  explosive  bullets. 

1038.  A gaseous  explosive  mixture  is  nearly  as  sudden 
in  its  action  as  an  explosive  compound,  for  it  contains  particles 
in  a state  of  perfect  mixture,  each  gas  acting  as  a vacuum  to 
the  others.  This  is  not  the  case  with  solid  explosive  mixtm-es ; 
therefore  these  latter  are  less  sudden  and  violent  in  their  action 
than  either  gaseous  mixtures  or  explosive  compounds. 

1039.  Intensity  of  the  Explosion. — Explosion  may  be  of 
different  degrees  of  intensity,  from  that  where  the  body  is  con- 
verted into  gas  by  gradual  combustion  up  to  detonation,  where 
the  whole  mass  of  the  body  is  suddenly  and  violently  converted 
into  gas  ; as  for  example  : when  gunpowder  is  ordinarily  fired, 
each  grain  commences  to  burn  on  the  sui’face,  the  burning 
gradually  extending  to  the  interior,  until  the  whole  is  con- 
sumed, while  nitro-glycerine  seems  always  to  detonate,  which 
partially  accounts  for  its  excessive  violence. 

1040.  Means  of  Causing  Explosion. — The  application  of 
heat  either  directly  or  indirectly  is  the  principal  means  of  caus- 
ing an  explosion.  Directily,  as  by  a match,  a red-hot  iron,  etc. 
Indirectly,  by  friction,  where  the  mechanical  energy  of  rubbing 
is  converted  into  heat ; by  percussion,  where  heat  is  generated 
by  the  direct  application  of  a blow ; or  by  concussion,  where 
heat  is  generated  by  a jar  or  shock  communicated  through  a 
second  body. 


374 


NAVAL  OEDNANCE  AND  GUNNEET. 


1041.  Method  of  Peodtjcing  Explosion. — The  circum- 
stances under  which  an  explosion  takes  place  create  a marked 
difference  in  the  effect  produced.  Every  one  is  familiar  with 
the  different  effects  produced  by  firing  gunpowder  in  the 
open  air  and  firing  it  in  a confined  space ; but,  apart  from  this, 
the  mode  by  which  it  is  fired  exercises  immense  infiuences, 
both  upon  the  force  and  the  rapidity  of  its  explosion. 

Suppose  that  a quantity  of  fulminate  of  mercumj  be  ex- 
ploded within  a mass  of  any  other  explosive ; apart  from  the 
name  produced,  a blow  will  be  given  by  the  gas  suddenly 
formed  by  the  fulminate,  which  will  act  upon  the  sm-rounding 
explosive  percussively,  like  the  blow  of  a hamme'r  upon  an 
anvil.  The  very  rapid  motion  of  the  particles  of  gas  will  give 
them  a force,  as  regards  any  resisting  body,  similar  to  that 
exercised  by  a solid,  having  a great  velocity,  against  any  obsta- 
cle in  its  path. 

1042.  DETONATIOhr. — "When  the  flame  of  the  fulminate 
is  applied  directly  to  the  explosive,  the  chemical  change  is 
initiated  at  the  point  of  application,  and,  if  the  flame  alone  were 
considered,  would  gradually  spread  from  this  point  through 
the  mass ; but  the  percussive  blow  is  extended  through  all  parts 
of  the  body  with  very  great  rapidity,  enormously  expediting 
the  speed  of  the  explosive  charge.  In  certain  cases  the  effect 
is  practically  simultaneous  throughout  the  whole  mass  of  the 
body  exploded,  thus  producing  detonation,  the  effect  of  which 
is  mueh  more  powerful  than  that  of  an  ordinary  explosion. 

1043.  Explosives  Capable  of  Detonation. — Each  explo- 
sive body  that  has  been  experimented  with  seems  to  have  a 
particular  mode  of  detonation,  and  probably  all  explosives  may 
be  detonated  if  the  right  method  of  doing  so  be  known.  Gun- 
cotton seems  to  have  a greater  range  of  susceptibility  to  differ- 
ent inodes  of  firing  than  any  other  explosive  agent.  It  can  be 
made  to  burn  slowly  without  explosion,  and  the  rapidity  of  its 
combustion  can  be  increased  up  to  the  point  of  detonation. 
Nitro-glycerine,  as  before  stated,  appears  always  to  detonate. 
(It  is  not  sensitive  to  flame  as  directly  applied.)  Fulminate  of 
mercury  is  a detonating  substance,  but  the  quantity  of  gas  given 
off  is  comparatively  small,  hence  the  limited  range  of  its  de- 
structive effect.  Gunpowder  is  said  to  be  capable  of  detona- 
tion, but  it  is  more  difficult  to  obtain  detonating  effects  with  it 
than  with  any  of  the  others. 

1044.  Detonation,  now  Pkoduced. — Detonation  can  only 
be  produced  by  the  application  of  the  requisite  blow  or  shock, 
and  this  is  usually  accomplished  by  means  of  a detonating  fuze 


EXPLOSIVE  AGENTS. 


375 


containing  the  required  amount  of  fulminate  of  mercury,  the 
amount  differing  for  each  explosive. 

Fulminate  of  mercury  has  been  found  to  be  by  far  the  best 
agent  for  producing  detonation  ; less  of  it  is  required  than  of 
any  other  explosive.  Nitro-glycerine  is  much  more  powerful 
than  fulminate  of  mercury,  but  while  a certain  amount  of  the 
latter  will  detonate  gun-cotton,  seventy  times  as  much  nitro- 
glycerine will  not  accomplish  it.  Chloride  of  Nitrogen  and 
Iodide  of  Nitrogen  are  much  more  violent  than  fulminate  of 
mercury,  yet  a larger  quantity  of  them  are  required  to  produce 
detonation.  These  facts  indicate  that  there  is  some  peculiarity 
in  the  impulse  given  by  the  firing  of  fulminate  of  mercury  that 
affects  other  explosives  more  powerfully  than  that  given  by 
any  other  body,  though  the  latter  may  he  the  stronger.  It  may 
be  considered  that  this  isowing  to  a peculiarity  of  vibration,  or 
wave  motion,  due  to  the  explosion  of  fulminate  of  mercury, 
which  causes  greater  disturbance  among  the  molecules  of  other 
explosives  than  the  vibrations  produced  by  any  other  explosives. 

1045.  Hatuke  of  Detonation. — Detonation  is  really  only 
an  exceedingly  rapid  explosion.  In  an  ordinary  explosion  like 
that  of  powder  in  a gun,  much  force  is  lost  by  the  slowness  of 
the  action.  As  gases  expand  heat  is  absorbed,  so  that  if  the 
gases  can  expand  as  they  are  formed,  much  of  the  heat  of  the 
chemical  reaction  is  absorbed,  diminishing  the  shaiqmess  of  the 
explosive  effects,  Avhich  is  therefore  not  sudden  but  gradual. 
With  a force  gradually  generated  and  exerted,  we  have  a 
propulsive  effect,  but  a detonation  has  a disruptive  violence, 
which  may  become  almost  irresistible. 

1046.  Illustrations  op  Explosion  by  Detonation. — The 
practical  value  of  this  mode  of  developing  the  force  of  explo- 
sive agents  is  very  great.  The  necessity  of  confining  gun- 
powder and  other  explosive  materials  in  strong  receptacles  for 
the  purpose  of  developing  their  explosive  force,  is  greatly  re- 
duced, and  indeed  entirely  dispensed  with  in  the  case  of  charges 
fired  under  water,  when  detonating  fuzes  are  used  as  the  ex- 
ploding agents. 

Masses  of  hard  material  of  great  size  or  strength,  such  as 
blocks  of  hard  rock,  large  iron  castings,  or  thick  bars  of  iron, 
may  be  broken  up  by  simply  placing  upon  one  of  their  surfaces 
a comparatively  small  charge,  quite  unconfined,  of  compressed 
gun-cotton,  or  of  a nitro-glycerine  preparation,  and  exploding 
it  by  means  of  a detonating-fuze. 

In  such  operations  the  destructive  effect  of  the  detonation 
will  be  increased  by  covering  the  charge  with  sand  or  other 
material,  but  in  hurried  operations  good  results  may  be  obtained 


376 


NAVAL  ORDNANCE  AND  GUNNERY. 


with  either  of  the  materials  specified  by  detonating  them  when 
freely  exposed  to  air. 

For  hasty  demolition  of  buildings  and  of  military  works, 
the  explosion  by  detonation  affords  most  important  facihties, 
reducing  the  difficulties,  dangers,  and  cost  of  such  operation  to 
a minimum. 


Section  II — Ma/nufacture  of  Gunpowder. 

1047.  Gunpowdee  is  the  agent  employed  for  the  firing- 
charge  of  all  ordnance,  and  for  the  bm’sting-charge  of  all  pro- 
jectiles. 

Its  use  depends  upon  the  fact,  that  at  the  moment  of  igni- 
tion, violent  deflagration  takes  place,  accompanied  by  the  evo- 
lution of  a large  volume  of  gas.  It  is  evident  that  if  the  ex- 
plosion occur  in  a limited  space,  a vast  pressure  accumulates 
and  becomes  a propulsive  foi’ce.  The  gas  produced  by  the  ex- 
plosion of  good  gunpowder  occupies  nearly  900  times  the  vol- 
ume of  the  powder  itself ; but,  owing  to  the  high  temperature, 
the  space  occupied  by  the  gas  at  the  moment  of  formation  is 
probably  3,000  times  greater  than  the  volume  of  the  powder. 

It  has  been  found  that  no  comj)osition  fulfils  so  many  requi- 
sites for  charging  fire-arms  as  a mixture  in  due  proportions  of 
nitre.)  charcoal^  and  sulphur ^ and  it  is  this  composition  which 
constitutes  gunpowder. 

The  ingredients  should  be  of  the  greatest  possible  purity, 
both  for  the  quality  of  the  powder  and  the  prevention  of  disas- 
trous accidents  in  the  manufacture. 

1048.  mGKEDIEXTS  OF  GUhrP01YDEE.--The  in- 
gredients for  the  manufacture  of  gunpowder  should  be  sup- 
plied in  the  rough  state,  and  refined  and  prepared  for  use  at  the 
factory,  in  order  to  insure  as  far  as  possible  uniformity  of  results 
in  manufacture  and  safety  in  carrying  it  on. 

It  is  manifestly  useless  to  attempt  to  obtain  powder  possess- 
ing uniform  qualities  unless  measures  are  taken  to  insure  the 
uniform  purity  of  its  constituent  elements  ; and  although  pres- 
ence of  chemical  impurities  may  be  readily  detected  in  samples 
of  refined  saltpetre  and  sulphur  supplied  by  contract,  and  though 
it  might  be  possible  to  devise  a series  of  practical  tests  for  the 
various  physical  qualities  by  purchase,  there  can  be  no  guarantee 
for  the  purity  of  the  former  and  uniformity  of  the  latter  equal 
to  that  of  careful  supervision  during  the  actual  processes  of  prep- 
aration and  refining. 


* Smith. 


MANTJFACTUIIE  OF  GUNPOWDER. 


377 


A manufacturer  wlio  refines  liis  own  saltpetre  and  sulpliur, 
and  burns  liis  own  charcoal,  has  means  of  insuring  the  purity  and 
uniformity  of  the  ingredients  of  which  he  makes  use,  far  supe- 
rior to  that  of  any  system  of  testing,  however  careful. 

1049.  The  additional  security  against  accidents  in  the  course 
of  manufacture,  gained  by  careful  exclusion  of  all  ^loreign  mat- 
ter from  the  ingredients  during  the  processes  of  refining,  is  of 
even  greater  consequence  in  the  manufacture  of  gunpowder. 
The  question,  how  far  the  too  frequent  explosions  in  powder 
factories  are  dependent  on  the  presence  of  minute  particles  of 
foreign  bodies  introduced  into  the  ingredients  after  refining  and 
before  they  come  into  the  hands  of  the  mixer,  has  not  received 
the  attention  which  it  deserves.  But  it  is  too  often  found  that 
though  care  be  taken  to  exclude  any  fragments  of  sand,  grit, 
etc.,  from  the  powder  from  the  time  it  leaves  the  mixing-house 
till  the  time  that  it  is  finished,  the  same  vigilance  is  not  exei’- 
cised  in  excluding  minute  particles  of  foreign  substances  from 
the  unmixed  ingredients,  by  which  negligence  the  subsequent 
precaution  is  altogether  thrown  away. 

1050.  Those  engaged  in  removing  saltpetre  from  the  refin- 
ery to  the  mixing-house  should  be  scrupulously  careful  not  to 
step  into  the  bins  where  it  is  stored  without  putting  on  clean 
magazine  shoes,  and  should  not  make  use  of  any  shovels,  bar- 
rels, etc.,  but  those  kept  specially  clean  and  free  from  grit  for 
the  purpose ; and  the  same  precautions  should  be  taken  in  hand- 
ling sulphur  and  charcoal,  the  latter  of  which  should  be  picked 
over  by  hand,  piece  by  piece,  before  being  ground,  and  after  that 
treated  with  the  same  care  as  the  other  ingredients.  If  pre- 
cautions to  avoid  accidents  are  worth  taking  at  all,  they  must,  to 
be  effectual,  be  commenced  whenever  the  ingredients  are  taken 
in  hand,  and  maintained  to  the  end  of  the  manufacture. 

1051.  Eefinixg  Sautpetee. — -The  principle  on  which  the 
process  depends,  is  that  saltpetre  is  greatly  more  soluble  in 
hot  than  in  cold  water,  while  the  impurities  generally  found 
in  it  do  not  present  the  same  disparity  in  their  solubility  at  dif- 
ferent temperatures.  Thus  a saturated  cold  solution  of  crude 
saltpetre  Avill,  as  its  temperature  is  raised,  take  up  a much 
greater  additional  quantity  of  saltpetre  proportionately  than  it 
Avill  of  the  other  salts  present.  Hence  if  a boiling  saturated 
solution  of  the  impure  salt  be  made  and  allowed  to  cool,  it  will 
deposit  the  excess  of  saltpetre  and  retain  the  other  salts  in  solu- 
tion. Boiling  Avater  will  take  up  39. G1  parts  of  chloride  of  so- 
dium, and  about  240  of  saltpetre.  W ater  at  the  temperature  of 
70°  will  take  up  about  36  of  the  former  and  about  32  of  the 
latter.  Consequently,  if  a boiling  solution  saturated  with  salt- 


378 


NAVAL  OEDNANCE  AND  GUNNEEY. 


petre  and  chloride  of  sodium  he  cooled  to  70°,  it  will  deposit 
about  208  parts  of  the  former  to  about  3.6  of  the  latter. 

All,  therefore,  that  has  to  be  done  in  refining  saltpetre  is  to 
make  a concentrated  solution  of  this  crude  material  at  a high 
temperature,  to  run  the  solution  into  fiat  troughs,  to  keep  it  in 
constant  agitation  as  it  cools  down,  and  then  to  renaove  from  it 
the  saltpetre  as  it  crystalizes  out  of  the  mother  litpior. 

1052.  Desceiption  of  the  Refixixg  Peocess. — Solution. 
— About  two  tons  of  crude  saltpetre  are  pressed  in  a large  open 
copper  pan  capable  of  holding  about  500  gallons  of  water,  and 
about  270  gallons  of  water  are  added  to  it.  This  is  generally 
done  over  night,  and  the  fires  are  lighted  under  the  copper  early 
the  following  morning.  Over  the  bottom  of  each  pan  is  placed 
a false  bottom  of  iron  perforated  with  holes  of  an  inch  in  diam- 
eter, to  allow  the  sand  and  insoluble  impurities  to  fall  to  the 
bottom.  In  about  two  hours  the  Avhole  of  the  saltpetre  will  be 
found  to  be  dissolved  and  the  solution  boiling,  and  the  specific 
gravity  of  the  solution  being  about  1.49,  it  reaches  the  tempera- 
ture of  230°  F.  The  false  bottoms  are  pulled  out  jrast  before 
the  solution  begins  to  boil,  and  the  scum,  containing  the  greater 
part  of  organic,  impurities,  is  removed  from  the  surface.  The 
solution  is  allowed  to  boil  for  about  half  an  hour  longer,  until 
no  more  scum  rises  to  the  surface ; the  copper  is  then  filled  up 
with  cold  water,  and  the  solution  again  boiled  briskly  for  a few 
minutes,  after  which  it  is  allowed  to  cool  down  to  become  of  a 
proper  temperature  for  being  pumped  into  coolers. 

1053.  Filtering. — The  filtering  process  is  almost  always 
used  when  refining  saltpetre  for  gunpowder-making,  but  is 
sometimes  omitted  when  refining  for  other  pm-poses.  In  tlie 
latter  case  the  solution  is  made  of  extra  strength  and  conse- 
quently denser,  and  the  cooler  being  placed  below  the  level  of 
the  coppers,  the  solution  is  run  directly  into  it  through  a pipe, 
the  orifice  of  which  in  the  copper  is  placed  at  a certain  height 
above  the  bottom,  to  prevent  the  sediment  running  out  with  the 
clear  liquor.  But  filtering  affords  a much  more  certain  plan  of 
obtaining  a clear  liquor  for  crystallization,  and  presents  little 
difficulty  and  causes  very  little  loss  of  time. 

1054.  When  the  temperature  of  the  solution  has  fallen  to 
220°  F.,  with  a specific  gravity  of  about  1.53,  it  is  ready  for 
pumping  into  the  filters.  AVhen  the  solution  has  arrived  at  the 
proper  temperature  for  the  ]U’Ocess,  a common  hand-pump  is 
lowered  into  the  copper,  and  the  solution  is  pumped  into  a 
wooden  trough  leading  to  another  larger  one,  termed  the  supply- 
trowjh,  furnrshed  with  six  holes  in  the  bottom,  beneath  which 
the  iilteriug-bags  are  suspended.  AVooden  plugs  are  provided 


MANUFACTURE  OF  GUNPOWDER. 


379 


for  these  holes  in  the  bottom  of  the  supplj-trongh,  so  that  if  the 
hags  become  clogged,  the  flow  of  solution  maj  be  stopped  till 
they  are  replaced  by  clean  ones. 

1055.  The  bags  are  suspended  on  iron  hooks  underneath 
the  holes  in  the  supply-trough.  They  are  always  rinsed  with 
hot  water  before  the  Altering  commences,  and  require  occasion- 
ally a little  poured  over  them  to  prevent  the  formation  of 
crystals  during  the  process,  which  would  clog  the  canvas  and 
prevent  the  solution  running. 

Occasionally  a solution  is  found  to  contain  so  much  organic 
impurity,  that  it  will  not  run  through  the  Alters.  In  this  case 
a little  glue,  about  1 lb.  to  2 tons  of  saltpetre,  is  added  to  the  so- 
lution in  the  copper,  which  has  the  effect  of  throwing  up  a 
great  part  of  the  impurity  as  a scum,  which  can  be  removed  be- 
foi'e  the  liquor  is  pumped  oirt. 

1056.  The  Altering  of  a copperful  of  liquor,  of  the 
strength  described  (Art.  1052),  takes  about  three-quarters  of  an 
hour.  As  soon  as  it  is  all  removed  from  the  copper,  the  pumps, 
which  are  suspended  overhead  on  a small  pulley,  are  pulled 
up  and  the  coppers,  if  necessary,  cleaned  out.  The  sediment, 
consisting  piincipally  of  sand  in  the  proportion  of  about  ^ per 
cent,  of  the  crude,  is  washed  and  the  washing  reserved  for 
evaporation.  A wooden  trough  placed  directly  underneath  the 
flltering-bags  receives  the  solution  as  it  runs  from  them,  and 
conducts  it  directly  into  the  cooler.  When  all  the  solution  is 
Altered,  the  bags  are  i-insed  with  hot  water  into  the  evaporat- 
ing-pots,  and  then  washed  and  hung  up  to  dry. 

1057.  Crystallization. — The  cooler,  or  crystallizing  cistern, 
is  a large,  shallow,  flat  trough  of  sheet  copper,  being  about  12 
feet  long,  7 feet  wide,  and  1 foot  deep.  By  the  time  the  solu- 
tion runs  into  it  the  temperature  will  have  fallen  to  between 
190°  and  180°  F.  As  the  temperature  continues  to  fall,  the  ex- 
cess of  saltpetre  crystallizes  out,  leaving,  of  course,  a considerable 
quantity  still  in  solution,  and  along  with  it  the  chemical  impu- 
rities of  the  crude  salt,  the  chlorides  and  sulphates. 

If  the  solution  were  left  to  crystallize  without  agitation,  the 
salt  would  be  deposited  in  the  form  of  large  crystals,  each  of 
which  would  pnclose  a small  quantity  of  this  impure  mother 
liquor.  To  prevent  this,  the  liquor  in  the  coolers  must  be  kept 
in  constant  agitation,  to  cause  it  to  deposit  the  salt  in  the  form 
of  flour.,  or  minute  crystals.  This  is  effected  by  a workman 
who,  for  the  Arst  hour  or  so,  until  the  temperature  of  the 
liquor  falls  to  about  90°,  keeps  it  constantly  stirred  by  means 
of  a large  wooden  hoe,  with  which  also  the  flow  is  drawn  to  the 
side  of  the  cooler,  to  be  shovelled  out  with  a copper  shovel. 


3S0 


NAVAL  ORDNANCE  AND  GUNNERY. 


As  it  is  removed,  it  is  fii’st  thrown  into  an  inclined  board,  or 
drainer^  to  allow  the  excess  of  lic[uor  to  run  back  into  the  cooler. 
It  remains  on  the  drainer  for  some  minutes,  after  which  it  is 
transferred  to  the  washing-vat. 

1058.  When  the  liquor  falls  in  temperature  to  about  90°  F., 
the  agitation  is  discontinued,  because  the  crystals  are  deposited 
much  more  slowly,  so  that  the  cost  of  labor  would  he  considera- 
bly increased.  The  crystals  which  are  deposited  at  a tempera- 
ture below  this  also  contain  a much  larger  quantity  of  mother 
liquor.  About  three  quarters  of  the  entire  Cjuaiitity  of  saltpetre 
is  removed  from  the  solution,  if  the  agitation  he  stopped  at 
90°  F. 


The  crystallizing  process  may  he  very  materially  hastened 
by  artificial  cooling.  In  some  refineries,  where  a good  fall  of 
water  can  he  obtained,  a stream  of  cold  water  is  made  to  ran 
under  the  bottom  of  the  cooler.  This  reduces  its  temperature 
very  rapidly,  and  causes  the  flour  to  he  deposited  with  less  loss 
of  time. 

1059.  The  mother  liquor  is  left  to  cool  down  after  the 
proper  amount  of  flour  has  been  removed  from  it.  As  soon  as 
its  temperature  approaches  that  of  the  atmosphere,  large  crystals 
are  deposited  in  the  cooler.  The  liquor,  still,  of  course,  a satu- 
rated solution  containing  all  the  original  soluble  impurities,  is 
run  off  and  reserved  for  subsequent  evaporation.  The  crystals 
are  scraped  off  and  transferred  to  the  refinery  copper  with  the 
next  charge  of  crude  salt. 

The  following  is  an  analysis  of  a sample  of  the  salts  left  in 


solution  in  the  liquor  : 

Saltpetre 77.10 

Chi.  Sodium 18.51 

Sulphate  of  Soda 3.39 

99.30 


— which  should  be  compared  with  the  anaysis  of  the  crude 
salt. 

1060.  Washing. — The  washing-vat,  to  which  the  saltpetre 
flour  is  transferred,  is  of  wood,  about  6 feet  long,  i wide,  and 
3|-  deep.  It  is  provided  with  a false  bottom  pierced  with 
small  holes,  underneath  which  is  a plug-hole  which  can  be 
closed  or  opened  as  required.  In  tliis  vat  the  saltpetre  receives 
three  waslfiugs,  the  first  being  given  at  once,  as  soon  as  it  is 
raked  from  the  strainers  into  the  vat,  to  remove  the  excess  of 
mother  liquor  still  adhering  to  it.  About  70  gallons  of  water 
are  run  through  the  vat,  and,  escaping  from  the  plug-hole  un- 
derneath the  false  bottom,  are  conducted  into  an  underground 


IiIANTJFACTURE  OF  GUNPOWDER. 


381 


tank.  The  second  washing  is  done  by  covering  the  crystals 
with  water  and  allowing  it  to  stand  for  half  an  honr,  the  ping 
being  in,  and  then  allowing  it  to  rnn  off  into  a second  nnder- 
gTonnd  tank.  The  crystals  are  allowed  to  drain  for  half  an 
honr  after  this  washing.  The  third  washing  is  given  by  run- 
ning about  100  gallons  of  Avater  through  the  crystals,  as  in  the 
first  Avashing,  the  plug-holes  remaining  open. 

The  Avater  from  the  third  washing  runs  into  the  tank  which 
receives  the  second,  the  contents  of  which,  being  comparatively 
free  of  impurities,  are  used  in  the  refining  coppers.  The  water 
from  the  first  Avashing  is  only  used  in  the  evaporating-pots.  It 
is,  of  course,  most  important  that  the  purest  water  should  be 
used  for  these  AAmshings.  Distilled  Avater  shoidd,  if  possible,  be 
alone  employed.  The  washings,  as  they  run  off,  are  saturated 
solutions  of  saltpetre ; but  they  take  up,  in  passing  through  the 
salt,  any  traces  of  chlorides  remaining  in  it. 

1061.  Tests. — Supposing  all  the  foregoing  operations  to 
have  been  properly  carried  on,  the  saltpetre  will  be  found  to  be 
perfectly  pure.  Should  it  be  deemed  necessary  to  test  it  for 
impurities,  it  should  be  subjected  to  the  folloAving.  A solution 
should  be  tested  : 

1.  With  blue  and  red  litmus  paper,  for  the  presence  of  an 
acid  or  alkali. 

2.  With  a solution  of  nitrate  of  silver,  for  the  presence  of 
chlorides,  which  Avould  throw  down  the  insoluble  chloride  of 
silver. 

3.  With  a solution  of  chloride  of  barium,  for  the  presence  of 
sulphates,  which  would  give  the  insoluble  sulphate  of  baryta. 

I.  With  a little  oxalate  of  ammonia,  for  lime,  AAdiich  would 
give  oxalate  of  lime. 

In  the  ordinary  practice  of  a refinery,  the  second  test,  viz., 
that  for  chlorides,  more  especially  the  chloride  of  sodium,  is  the 
only  one  ever  used. 

1062.  The  saltpetre  is  transferred  to  the  store  bins  gener- 
ally the  day  after  it  is  refined.  In  removing  it  from  the  wash- 
ing vats,  about  six  inches  deep  at  the  bottom  is  left,  as  it  con- 
tains a great  deal  of  Avater.  After  remaining  in  the  bins  three 
or  four  days,  it  will  be  found  to  contain  from  three  to  five  per 
cent,  moisture,  according  to  the  season.  It  remains  in  the  bins 
till  required  for  use  in  the  mixing-house,  the  saltpetre  used  for 
poAvder-making  being  always  used  moist. 

1063.  Drying. — Should  a supply  of  refined  saltpetre  be  re- 
quired for  storage  or  transport,  the  salt  is  generally  dried  before 
being  placed  in  ban’els.  This  is  done  in  a hot-chamber  : a small 
room  with  a stone  floor,  underneath  Avhich  runs  a flue ; and  pro- 


382 


NAVAL  ORDNANCE  AND  GUNNERY. 


vided  with  racks  inside,  on  whick  are  placed  the  flat  copper 
trays  containing  the  saltpetre. 

The  hot-chamber  is  capable  of  containing  two  or  three  tons 
of  saltpetre,  and  the  teinperatnre  is  generally  raised  to  about 
220°  F.,  which  dries  it  completely  in  from  four  to  six  hours. 
The  salt  is  covered  in  a flat  tray,  placed  outside  the  store  before 
being  baiTelled  up. 

1064.  Extraction  of  Saltpetre  from  Damaged  Powder. — 
The  extraction  of  saltpetre  from  powder  sweepings,  a consider- 
able cpiantity  of  which  accumulates  in  the  course  of  manufacture, 
and  from  powder  which  may  have  been  accidentally  wetted  or 
damaged  by  long  storage  in  damp  magazines,  forms  a part  of 
the  ordinary  nature  of  duties  in  a refinery  of  saltpetre.  Copper 
pans  are  used  for  stirring  the  sweepings,  and  any  damaged 
powder  which  may  be  sent  to  the  factory  is  also  placed  in  pans. 
As  a precaution,  the  contents  of  each  pan  are  carefully  and 
thoroughly  melted,  and  the  supply  is  not  allowed  to  become 
dry  by  evaporation. 

1065.  The  Operation. — About  240  gallons  of  water  are 
pumped  into  a copper  of  400  gallons  capacity,  and  brought 
nearly  to  the  boiling-point.  Pure  water  must  be  used  for  the 
first  day’s  operation,  but  afterwards  the  liquors  obtained  in  fil- 
tering the  previous  day’s  work.  About  900  bbls.  of  the  dam- 
aged powder  are  then  thro^vn  in,  care  being  exercised  that  it  is 
thoroughly  wetted  throughout  before  being  brought  into  the 
extracting-house.  The  mixture  is  stiiTcd  and  boiled  for  three- 
quarters  of  an  hour,  after  which  the  fire  is  damped  and 
the  solution  ladled  into  filters  of  coarse  sheeting.  From 
the  first  series  of  filters,  the  solution  passes  to  a second 
row,  through  which  it  passes,  clear,  into  a tank.  From  the 
tank  it  is  subsequently  pumped  into  the  evaporating-pots  and 
boiled  down.  The  saltpetre  being  of  course  pure,  the  boiling  is 
merely  to  drive  off  a certain  quantity  of  water.  AYhen  suffi- 
ciently reduced  it  is  again  filtered  and  crr-stallized  in  small  cop- 
per pans.  The  crystals  obtained  are  used  a s crude  saltpetre. 
The  carbon  and  sulphur  obtained  are  thrown  on  the  waste-heap, 
being  of  no  value. 

1066.  The  whole  process  of  extraction  is  dirty  and  trouble- 
some, and  the  expediency  of  carrying  it  on  to  any  great  extent 
depends  on  the  price  of  saltpetre  at  the  time,  and  the  price 
which  can  be  obtained  in  the  market  for  damaged  powder. 
Powder  sweepings  should  of  course  always  be  extracted,  as  they 
are  liable  to  contain  particles  of  foreign  substances ; but  pro- 
vided powder  be  merely  old  and  dusty,  it  may  still  be  well 
adapted  for  blasting  operations,  and  may  command  a good  price. 


MANUFACTURE  OF  GUNPOWDER. 


383 


1067.  About  94  per  cent,  of  the  saltpetre  contained  in  pow- 
der can  always  be  obtained  by  extraction,  against  the  value  of 
which  must  be  set  otf  the  cost  of  the  men’s  wages  employed  in 
the  process,  the  amount  of  fuel  expended,  etc. 

1068.  Sulphur. — The  sulphur  used  in  gnnpowder-making 
is  imported  from  Sicily.  The  finest  quality  is  alone  employed. 
As  imported,  the  sulphur  contains  from  three  to  four  per  cent, 
of  earthy  impurities,  having  already  undergone  a rough  purifi- 
cation by  distillation  before  it  comes  into  the  merchant’s  hands. 
It  is  finally  and  carefully  purified  at  the  factories  by  a second 
distillation. 

1069.  The  substance  exists  in  several  distinct  conditions  or 
forms,  two  of  which  require  special  notice,  viz.,  the  soluble,  or 
electi’o-negative  form,  and  the  insoluble,  or  electro-positive.  Dis- 
tilled sulphiu’  consists  almost  entirely  of  the  former.  Sublimed 
sulphur,  contains  a large  proportion  of  the  latter.  Distilled 
sulphur,  as  used  in  the  manufacture  of  gunpowder,  consists  of 
masses  of  clear  yellow  crystals  in  the  form  of  rhombic-octahe- 
dra,  and  is  readily  soluble  in  bisulphide  of  carbon.  Sublimed 
sulphur,  known  a.?,  flowers  of  sulphur^  is  a pale  yfellow  powder, 
composed  of  minnte  particles  wdiich  do  not  present  a crystalline 
structure,  but  which  are  merely  minnte  granules  consisting  of 
insoluble  sulphur,  enclosing  a small  portion  of  the  soluble 
variety.  This  latter  form  of  sulphur  is  to  a great  extent  insol- 
ble  in  the  bisulphide. 

1070.  Description  of  Refining  Apparatus.  — The  apparatus 
employed  consists  of  a large  pot  of  cast-iron,  A (Fig.  253),  set  in 
brick  work,  the  metal  being  very  thick.  Round  the  top  edge 
is  shrunk  a strong  ring  or  tire  of  'wrought-iron,  to  prevent  split- 
ting by  explosion.  On  the  top  is  fitted  a large  dome-shaped 
cover,  also  of  cast-iron,  secured  to  the  pot  by  three  wrought-iron 
tie-rods,  which  are  secured  by  screw-bolts  to  a wrought-iron 
ring  passing  round  the  neck  of  the  cover.  At  the  top  of  the 
cover  is  a circular  opening  fitted  with  a heavy  cast-iron  lid,  the 
w'eight  of  which  is  sufficient  to  keep  it  in  its  place  during  the 
refining  process.  In  this  lid  is  an  iron  plug-hole  having  con- 
siderable taper,  through  which  the  pot  is  charged.  The  cast- 
iron  plug  which  closes  it  fits  sufficiently  tight  to  prevent  escape 
of  sulphur-vapor,  particularly  if  a little  sand  be  thrown  over  it ; 
but  at  the  same  time  it  acts  as  a safety-valve,  being  lifted  out 
if  an  unusual  pressure  of  vapor  is  exerted  inside  the  pot. 

1071.  From  the  dome-shaped  cover  two  pipes  proceed  at 
right  angles  to  each  other,  one  to  the  subliming-dome,  the  other 
to  the  distilling-tank,  or  receivingpot.  The  first  pipe  is  fur- 
nished with  a throttle-valve  (Fig.  254),  D,  which  can  be  closed 


384 


NAVAL  ORDNANCE  AND  GUNNERY. 


or  opened  by  a handle  from  without.  The  other  pipe  is  encased 
in  a water-jacket,  and  can  also  be  closed  or  opened  by  means  of 


Fig.  253. — Ground  Plan  of  Sulphur-refining’  Apparatus. 

A.  Melting  Pot. 

B.  Pipe  with  Water  Jacket  leading  to  C. 

0.  The  Receiving  Pot. 

D.  Pipe  leading  to  Subliming  Dome. 

a valve.  When  distilling,  a constant  flow  of  water  is  main- 
tained through  the  water-jacket  (Fig.  255).  An  escape  pipe  fltted 
to  tliis  jacket  allows  of  the  escape  of  water  when  tliere  is  a sudden 
development  of  steam  caused  by  the  heat  of  the  sulphur  vapor. 

1072.  The  receiviug-pot,  C,  is  merely  a large  circular  vessel 
of  cast-iron,  which  is  set  on  a frame  inserted  in  small  trucks,  to 
allow  of  a slight  movement  Avhen  the  pipe  which  connects  it 
with  the  melting-pot  becomes  expanded  and  lengthened  by  the 
heat  of  the  sulphur  vapor  passing  through  it.  There  is  a large 
circular  opening  in  the  lid  through  which  the  melted  sulphur 
can  be  ladled  out  when  necessary.  This  opening  is  closed  by 
an  iron  lid  similar  to  that  of  the  melting-pot,  in  which  is  also  a 
small  plug-hole  through  which  the  depth  of  melted  sulphur  in 
' the  receiving-pot  can  be  ganged  witii  an  iron  rod.  A small 
pipe  leads  from  another  opening  in  the  lid  of  the  receiving-pot 
into  a square  wooden  chamber  lined  with  lead  to  receive  any 
new  condensed  vapor,  and  saves  it  to  deposit  its  sulphur  in  the 
form  of  flowers.  This  chamber  is  provided  with  a tall  chim- 
ney, also  of  wood,  containing  a series  of  steps  or  traps  to  catch  as 
much  of  the  flowers  sls,  possible. 


MAinJFACTTJEE  OF  GENPOWDEE. 


385 


1073.  The  siTbliming-dome  is  a large  dome-shaped  building 
of  brick,  E (Fig.  251).  The  pipe  for  the  sulphur-pot  enters  it 


Fig.  — Sulpur  Eefinmg  Pot  and  Dome. 


near  the  top.  The  chamber  is  lined  with  flag-stones,  and  the 
floor  is  covered  with  sheet-lead.  It  is  provided  with  two  doors, 
an  inner  one  of  iron,  an  outer  one  of  wood  lined  with  sheet- 
lead,  both  close  fitting,  through  which  passes  a pipe  to  allow  tlie 
escape  of  air.  This  pipe  terminates  in  a vessel  of  cold  water. 

1071:.  Process  of  Refining. — If  distillation  alone  is  to  be 
carried  on,  about  5|-  cwt.  of  crude  sulphur  are  placed  in  the  pot 
each  morning.  An  extra  hundred-weight  must  be  put  in,  if 
both  distillation  and  subliming  are  to  be  carried  on  together.  The 
fire  being  lighted,  the  conical  cast-iron  plug  is  left  out  of  the 
hole  in  tlie  lid  of  the  pot,  the  passage  into  the  dome  is  opened, 
and  that  into  the  receiving-pot  closed.  The  heat  is  maintained 
for  three  hours  till  the  sulphur  is  of  a proper  temperature  for 
distillation.  The  vapor  which  first  rises  from  the  pot  is  of  a 
pale  yellow  color,  and  as  much  of  it  as  passes  into  the  dome 
falls  down  condensed  as  flowers  of  sulphur.  But  at  the  end 
of  three  hours  the  vapor  becomes  of  a deep  reddish-brown 
color,  showing  that  the  temperature  of  the  melted  sulphur  has 
reached  the  proper  point. 

The  plug  must  then  be  inserted  in  the  lid,  the  communi- 
cation to  the  dome  closed,  and  that  leading  to  the  receiving- 
pot  opened,  allowing  the  heavy  vapor  to  pass  through  the  pipe 
surrounded  with  the  water-jacket,  by  means  of  which  a con- 
stant circulation  of  cold  water  is  kept  up  round  it.  In  this 
way  the  sulphur  vapor  is  condensed,  and  runs  down  into  the 
25 


386 


NAVAL  ORDNANCE  AND  GUNNERY. 


receivin,o;-pot  as  a clear  orange  liquid  resembling  molasses  in 
color  and  consistency. 

1075.  The  person  who  watches  tlie  operation  knows,  bv 
gauging  the  depth  of  the  melted  sulphur  in  the  receiving-pot, 
when  the  greater  part  of  the  material  has  distilled  over.  He 
then  lowers  the  fire,  opens  the  communication  into  the  dome. 


and  cuts  off  that  leading  to  the  receiving-pot,  allowing  the  re- 
maining sulphur  to  pass  off  into  the  dome  as  flowers.  A low 
fire  is  maintained  till  the  whole  has  been  driven  off,  leaving  the 
eartliy  residue  quite  free  from  it,  and  consequently  loose  like 
coal-ashes,  so  that  it  may  be  easily  ladled  out  before  recharging 
the  pot. 

1070.  When  both  subliming  and  distillation  are  cairied  on  at 
once,  the  first  part  of  the  process  would  be  exactly  as  described 
above ; but  when  the  distillation  was  finished  the  fire  would  be 
maintained  for  the  remainder  of  the  day,  but  somewhat  lower, 
to  dnve  off  the  quantity  required  into  the  dome.  And  in  this 
case  the  subliming  process  would  be  carried  on  for  several  days, 
and  the  pot  and  dome  never  allowed  to  cool  down  altogether 
till  the  required  (piantity  of  flowers  of  sulphur  had  been  ob- 
tained. 

1077.  It  is  of  the  greatest  consequence  that  the  fires  should 


mmrFACTURE  of  gunpowder. 


387 


be  carefully  regulated  in  all  cases,  for  if  the  heat  become  too 
great  and  the  temperature  of  the  melted  sulphur  be  allowed  to 
rise  to  836°,  the  vapor  disengaged  at  that  temperature  is  highly 
explosive  when  mixed  with  common  air ; and  if  the  ping  be 
driven  out  by  the  pressure  of  the  vapor,  or  if  air  be  drawn  into 
the  pot  through  some  leakage  in  the  pipes,  an  explosion  invari- 
ably happens. 

1078.  When  the  distilled  sulphur  in  the  remaining  pot  has 
cooled  down  sufSciently,  which  it  will  do  in  the  course  of  an 
hour  or  two,  it  is  ladled  by  hand  into  wooden  tubs  and  allowed 
to  solidify.  These  tubs  are  constructed  of  a number  of  loose 
staves  held  together  by  broad  wooden  hoops,  which  can  be 
struck  off  when  the  sulphur  has  set,  allowing  the  staves  to  fall 
asunder  and  leave  it  as  a solid  cylindrical  mass. 

1079.  Distilled  sulphur  immediately  after  being  removed 
from  the  tubs  is  placed  within  a boarded-otf  enclosure,  to  guard 
against  coming  in  contact  with  any  fragments  of  grit  or  sand 
which  might  thus  enter  the  powder,  and  is  broken  up  into  larger 
lumps,  which  are  sent  up  to  the  factory  to  be  ground  under  a 
small  pair  of  millstones.  After  being  ground  it  is  reeled  through 
32-mesh  wire-cloth,  and  is  then  fit  for  the  mixing-house. 

1080.  Testing. — Its  fitness  for  use  as  an  ingredient  of  gun- 
powder may  be  readily  tested : 

1st.  By  burning  a small  quantity  on  porcelain,  when  the 
amount  of  residium  should  not  exceed  0.25  per  cent. 

2d.  By  boiling  with  water  and  testing  with  blue  litmus  pa- 
per, which  it  should  only  very  feebly  redden. 

1081.  Use  as  an  Ingredient  of  Gunpowder. — As  an  ingre- 
dient of  gunpowder,  sulphur  is  valuable  on  account  of  the  low 
temperature  (560°  F.),  at  which  it  inflames,  thus  facilitating 
the  ignition  of  the  powder.  Its  oxydation  by  saltpetre  appears 
also  to  be  attended  with  the  production  of  a higher  temperature 
than  is  obtained  with  charcoal,  which  would  have  the  effect  of 
accelerating  the  combustion,  and  of  increasing  by  expansion  the 
volume  of  gas  evolved. 

1082.  Chaecoal. — The  woods  from  which  charcoal  is  now 
manufactured  for  powder-making,  appear  to  have  been  in  use 
from  a very  early  period.  Modern  research  has  shown  that 
there  was  a good  reason  for  their  selection,  and  that  the  cause 
of  their  superiority  over  all  other  woods  is  probably  that  their 
charcoal  when  burnt  with  saltpetre  and  sulphur  yields  larger 
volumes  of  gas  than  any  others. 

1083.  TJie  Woods  tlsed. — The  woods  generally  used  for  the 
best  gunpowders  are  the  willow,  the  alder,  and  what  is  popiilarly 
known  as  the  hlack  dogwood.  The  more  rapidly  a wood  has 


388 


NAVAL  ORDNANCE  AND  GUNNERY. 


been  grown,  the  less  dense  will  it  be,  and  the  better  for  powder- 
making when  converted  into  charcoal.  The  vnllovj  is  one  of 
the  sottest  and  lightest  of  woods ; it  is  of  very  rapid  growth, 
nearly  white,  and  has  a tolerably  large  circnlar  white  pith.  The 
alder  is  somewhat  harder  and  denser  in  texture  than  the  willow, 
and  is  not  of  such  rapid  growtln  Its  color  is  reddish-brown, 
and  the  pith  is  triangular  in  section.  The  dogwood  i?,  dense  and 
tough,  of  slow  growth,  and  having  circular  pith  of  a reddish  color. 

1081.  Small  wood  of  about  ten  years’  growth  is  preferred  for 
powder-making.  Alder  and  willow  of  this  age  will  be  probably 
four  or  five  inches  in  diameter,  dogwood  about  one.  The  wood 
must  be  straight,  perfectly  sound,  and  entirely  free  from  bark, 
and  must  be  felled  in  the  spring.  Great  sti-ess  is  laid  on  the 
cleanliness  of  the  wood.  Any  traces  of  bark  adhering  to  it  are 
not  to  be  tolerated.  If  the  wood  is  cut  in  the  spring  when  the 
sap  is  rising,  the  bark  is  easily  removed,  and  the  wood  is  left 
])erfectly  clean.  Wood  cut  at  any  other  season  of  the  year  is 
■just  as  good,  only  in  this  case  the  removal  of  the  bark  is  a much 
more  difficult  matter. 

1085.  To  Convert  the  Wood  into  Charcoal. — W ood  is  con- 


verted into  charcoal  in  iron  retorts  or  cylinders,  set  into  bnck- 
work.  Fig.  256  shows  a transverse  section  of  a set  of  cylindere, 


MANUFACTURE  OF  GUNPOWDER. 


389 


giving  tlie  arrangement  of  tlie  fines,  by  wliieli  tlie  flame  is  made 
to  play  all  around  them ; and  Fig.  257  shows  a longitudinal 
section  of  one  cylinder,  showing  how  the  second  cylinder,  or 
slip.  A,  containing  the  wood  is  placed  in  its  interior,  and  the  ar- 
rangement of  pipes  hy  which  the  gaseous  matter  evolved  from 
the  wood  is  conducted  into  the  fire. 

1086.  Each  cylinder  is  made  of  cast-iron,  having  two  pipes 
passing  out  at  the  inner  end  of  it.  When  set,  the  lower  one  of 
these  is  closed  with  hrick-work,  the  upper  one  only  being  used, 
and  the  lower  one  being  only  intended  for  use  should  the  cylin- 
der be  turned  round  and  reset.  To  the  uppermost  pipe  is  at- 
tached a branch  pipe  leading  to  a horizontal  pipe  extending  be- 
hind the  whole  set  of  cylinders,  from  one  end  of  which  another 
pipe  descends  perpendicularly,  joining  another  leading  directly 
into  the  former.  Each  cylinder  has  a false  bottom  of  brick- 
work, in  front  of  which  is  bolted  on  a piece  of  wrought-iron 
plate  having  a cylinder  hole  corresponding  to  the  uppermost 
pipe  of  the  cylinder.  The  cylinders  are  closed  with  tight-fitting 
iron  doors  secured  by  a powerful  screw,  much  in  the  same  way 
as  the  ends  of  gas  retorts  are  fastened. 

1087.  For  convenience  of  handling,  the  wood  is  placed  in 


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Tig.  257. — Longitudinal  Section  of  Retort, 

email  cylinders  of  sheet-iron,  A,  termed  slips^  which  are  placed 
on  small  iron  travelling  carriages,  on  which  they  can  be  run  up 


390 


NAVAL  ORDNANCE  AND  GUNNERY. 


dii’eetly  to  tlie  month  of  the  cylinders  and  shot  in.  The  back 
end  of  each  slip  is  provided  with  a handle  to  facilitate  with- 
drawal. The  slips  are  a little  over  three  feet  in  length  so  as 
just  to  take  the  cord-w'ood  in  easily. 

1088.  Provided  the  cylinders  are  hot,  the  wood  is  thoroughly 
charred  in  two  or  three  hours.  The  plan  of  conducting  the  gas 
and  tar  from  the  wood  into  the  fire  is  found  greatly  to  economize 
fuel,  and  to  he  the  readiest  means  of  ascertaining  when  the  char- 
]-ing  is  properly  and  thoroughly  done.  This  is  shown  by  the 
flame  wliieh  issues  from  the  pipe  leading  into  the  fire  becoming 
of  a v^iolet  tint,  indicating  the  formation  of  carbonic  oxide. 

As  soon  as  this  is  observed  the  doors  of  the  cylinders  are 
opened,  the  slips  are  hoisted  out  and  lowered  into  large  iron 
extinguishers  having  close-fitting  lids,  in  which  they  remain  for 
half  a day,  after  which  the  ehai'coal  is  shot  into  coolers — large 
cylindrical  eases  of  sheet-iron  fitted  with  lids — and  sent  to  the 
cliarcoal  store.  Wood  yields  about  25  per  cent,  of  charcoal. 

1089.  Effect  of  Temperature  employed  in  Conversion. — It  is 
of  the  higliest  importance  that  the  charring  of  the  wood  should 
always  he  conducted  as  neaily  as  possible  at  the  same  temper- 
ature ; for  the  chemical  composition  of  the  charcoal  and  the 
temperature  at  which  it  will  igirite  is  undoubtedly  affected  by 
the  temperature  at  which  it  has  been  charred.  Charco.al  pre- 
pared at  a low  temperatm-e  is  softer,  more  inflammable,  and 
contains  more  gaseous  elements  than  charcoal  pi-epared  at  a 
higher  heat,  and  the  gunpowders  made  from  these  charcoals 
wmuld  be  similarly  affected.  It  is  hopeless,  therefore,  to  at- 
tempt to  ohtai]i  uniform  results  in  manufacturing  powder,  unless 
means  be  taken  to  insure  uniformity  in  the  preparation  of  char- 
coal. 

1090.  Qualities  of  Charcoal. — The  fitness  of  charcoal  for 
gunpowder  depends  on  its  chemical  composition,  which  is  indi- 
cated by  its  physical  cpialities.  If  properl}-  made  it  should  be 
jet-black  in  color,  its  fracture  should  show  a clear,  velvet-like 
surface,  and  it  should  be  light  and  sonorous  when  dropped  on 
a hard  surface. 

Underburnt  charcoal,  that  is,  charcoal  that  is  prepared  at  a 
very  low  temperature,  is  at  once  known  by  its  reddish-brown 
color ; overburnt  charcoal,  by  its  hardness  and  density.  The 
former  is  greatly  more  infiammal)le  than  the  latter,  charcoal 
prepared  at  a temperature  of  500°  F.  being  readily  ignited  at 
a temperature  of  G10°  F.,  while  charcoal  prepared  at  1800°  F. 
requires  a temperature  neaily  double  the  last  to  inflame  it. 

1091.  Underbunit  charcoal  has  found  favor  for  some  small- 
arm  powders.  It  certainly  appears  to  render  the  powder  more 


MANUFACTUEE  OF  GTJNPOWDEE. 


391 


inflammable,  and  consequently  quicker,  but  it  has  the  disadvan- 
tage of  being  more  hygroscopic  thau  denser  charcoal,  and  of 
rendering  the  powder  therefore  more  liable  to  suffer  damage 
from  damp.  That  underburnt  charcoal  produces  a very  marked 
effect  on  gunpowder  there  can  be  no  doubt.  Recent  experi- 
ments have  proved  that  if  two  powders  be  made  identical  in  all 
other  qualities,  the  one  with  black  charcoal,  the  other  with  red 
or  underburnt  charcoal,  the  latter  will  give  a higher  velocity  to 
the  projectile  than  the  former.  Powder  made  from  underbiu’nt 
charcoal  can  be  readily  distinguished,  when  crushed  to  line  dust, 
by  its  color. 

1092.  Peopojstions  of  Ingeedients. — In  determining  the 
proportions  in  which  the  constituents  should  be  mixed,  the 
circumstances  in  which  it  is  to  be  used  must  be  considered. 

A.  vast  number  of  experiments  have  been  made  at  various 
times  to  discover  the  proportions  of  nitre,  sulphur,  and  charcoal 
best  adapted  for  the  production  of  gunpowder.  It  has  been 
found  that  no  general  rule  can  be  given  which  shall  fulfil  every 
requirement,  yet  all  nations  appear  to  have  found  by  trial  the 
proportions  most  generally  useful  for  ordinary  purposes,  and 
they  all  approximate  to  the  percentages  required  by  the  formula 
2KRO,  + S -f  3C, 
supposing  the  charcoal  to  be  pure  carbon. 

The  percentage  composition  is  generally  thus  : 


Kitre 74.8 

Sulphur 11.9 

Charcoal 13.3 


The  percentage  of  nitre  varies  from  70  to  80  ; that  of  sul- 
phur and  charcoal  from  10  to  15  each. 

The  best  powder  is  intended  for  war  and  sporting  purposes, 
and  contains  usually  a little  less  sulphur  and  a little  more  char- 
coal than  the  above. 

1003.  The  proportions  required  by  regulation  for  gunpow- 
der in  the  United  States  services  are  : 


Nitre 75 

Charcoal 15 

Sulphur 10 


These  proportions  are  not  those  which  theoretically  would 
give  the  greatest  amount  of  gas.  The  charcoal  is  in  excess,  to 
allow  for  ash,  and  the  sulphur  is  diminished,  as  it  acts  injuri- 
ously on  the  metal  of  the  piece  by  the  formation  of  a sulphide 
of  iron,  which  eats  away  the  surface  of  the  bore. 

When  the  proportion  of  charcoal  is  greater  than  that  con- 
tained in  commoir  powder  it  will  be  less  completely  and  rapidly 
burned. 


392 


NAVAL  ORDNANCE  AND  GUNNERY. 


1094.  Blasting  Powder,  for  example,  contains  a greater 
proportion  of  charcoal  and  less  nitre ; its  action  is  consequently 
slower,  and  if  used  in  fire-arms,  not  only  is  the  piece  very 
soon  rendered  foul,  but  the  hall  is  projected  to  a much  less 
distance. 

This  alteration  in  the  proportions  is  mainly  on  account  of 
the  great  reduction  in  price  thereby  effected. 

1095.  Preparing  and  Mixing  the  Ingredients. — Before 
the  ingredients  can  be  mixed,  they  must  be  reduced  to  a pow- 
der sufficiently  tine  for  the  purpose.  It  is  important  to  bear 
clearly  in  mind  the  meaning  of  the  terms  mixing  and  incorpo- 
rating, as  they  are  used  by  gunpowder-makers.  Though  gun- 
powder is  really  only  a mixture,  very  intimate,  no  doubt,  of 
the  three  ingredients,  and  not  a new  chemical  substance  formed 
out  of  them,  yet  by  mixing  is  understood  only  the  stirring  to- 
gether for  a few  minutes  of  the  saltpetre,  sulphur,  and  charcoal, 
to  get  them  perfectly  distributed  amongst  each  other;  and  by 
incorporating,  the  long-continued  trituration  and  grinding  wliich 
the  mixture  undergoes  under  heavy  edge-runners,  by  which  a 
mass  of  the  ingredients  becomes  transformed,  from  a mere 
mixture  of  three  different  substances  into  gunpowder.  A pre- 
liminary mixing,  such  as  is  employed  at  most  gunpowder- 
works,  may  be  dispensed  with ; incorporation,  wliether  per- 
formed by  pestle  and  mortar,  in  the  stamping-mill,  or  under 
edge-runners,  never. 

1096.  If  the  saltpetre  is  used  moist,  an  allowance  for  this 
must  be  made  in  weighing.  The  percentage  of  moisture  in  the 
cpiantity  used  is  ascertained  by  drying  and  pressing  a sample, 
and  comparing  the  weight  before  and  after  the  operation.  In 
this  country  it  is  found  highly  advantageous  to  have  the  salt- 
petre dried  and  pulverized  before  weighing  out. 

1097.  Occasionally  dried,  refined  saltpetre  may  be  employed 
for  manufacture  in  the  case  of  a stoppage  in  the  saltpetre  re- 
finery. In  this  case  the  dried  salt  is  first  ground  under  a pair 
of  small  stone-edge  runners,  fitted  vdth  scrapers  to  iirevent  the 
salt  adhering  to  them,  and  then  passed  through  a slope  reel 
covered  with  28-mesh  wire,  that  which  passes  through  the 
wire  being  used  for  mixing,  the  larger  fragments  being  re- 
ground. 

1098.  The  sulphur  is  ground  in  quantities  of  2-^-  cwts.  at  a 
time,  under  a pair  of  iron  edge-runners,  also  fitted  with  scra- 
pers, and  sifted  in  a slope-reel  covered  with  32-mesh  wire. 

1099.  Charcoal,  after  being  carefully  hand-picked,  to  guard 
against  the  introduction  of  any  fragments  of  foreign  matter 
and  underburut  knots  of  wood,  is  groimd  in  a mill  resembling 


MANUFACTURE  OF  GUNPOWDER. 


393 


a coffee-mill  in  action.  (Fig.  258.)  It  consists  of  a cone  work- 
ing in  a cylinder,  each  being  firmished  with  diagonal  ribs,  or 
teeth,  wliich  are  widely  apart  at  top,  but  approach  closely  to- 


A. — Cylinder.  B.- — Cone.  K.— Reel. 

gether  at  bottom.  The  charcoal,  which  is  shot  in  at  the  top, 
passes  out  at  the  bottom  into  a slope-reel,  covered  with  32-mesh 
wire,  all  fragments  which  do  not  pass  throxigh  being  trans- 
ferred again  to  the  mill. 

1100.  An  important  caution  must  be  mentioned  in  connec- 
tion with  the  grinding  of  chai'coal.  After  being  burnt  it 
should  be  allowed  to  stand  for  a considerable  time — ten  days  to 
a fortnight — before  being  ground  ; for  when  ground  fresh  after 
burning,  the  finely  powdered  charcoal  absorbs  and  condenses 
oxygen  so  rapidly  as  to  generate  a great  amount  of  heat ; enough, 
in  so  bad  a conductoi’,  to  cause  spontaneous  combustion.  In- 
stances of  fires  in  gunpowder  factories  from  this  cause  are  on 
record,  fresh-ground  charcoal  having  been  left  overnight  in 
wooden  bins. 

1101.  Mixing-Machine. — The  relative  proportions  of  the 
three  ingredients  are  weighed  out  in  quantities  of  50  lbs.,  and 


394 


NAVAL  ORDNANCE  AND  GUNNERY. 


transferred  to  tlie  mixing-machine.  ("Fig.  259.)  This  consists 
of  a hollow  drum  of  gun-metal,  which  is  made  to  revolve  at  a 


Fig.  259. — Mixing-machine. 


speed  of  40  revolutions  per  minute.  The  hearings  of  this 
drum  are  hollow,  to  receive  a shaft  which  passes  through  them. 
This  shaft  carries  in  the  interior  of  the  drum  a series  of  44 
arms,  or  diers,  tlie  points  of  which  just  clear  the  interior  of  the 
drum,  and  revolves  at  twice  the  speed  of  the  drum,  and  in  the 
opposite  direction. 

1102.  A 50-lb.  hag  of  ingredients  is  emptied  into  the  drum 
through  a scpiare  opening  at  the  top  of  it,  and  the  drum  and 
shaft  carrying  the  lliers  being  set  in  motion  for  five  minutes, 
the  saltpeti-e,  sulphur,  and  charcoal  are  thoroughly  mixed  to- 
gether. The  opening  at  the  bottom  of  the  drum  allows  the 
mixed  ingredients  to  fall  down  the  shoot  into  a tub,  from  which 
they  ai’e  transferred  to  an  8-mesh  wire  sieve  placed  over 
another  shoot  having  a composition-bag  placed  beneath  it.  On 
the  sieve  the  charge  is  carefully  sifted  by  hand,  to  guard 
against  any  foreign  matter,  such  as  splinters  of  wood  from  the 
saltpetre  bins,  etc.,  pas.smg  into  it,  and  falls  through  into  the 
bags,  in  which  it  is  tied  up  tightly  and  transferred  to  the  charge- 
house,  ready  for  the  incorporating-mill. 

1103.  Incorpokation. — Incorporation  is  unquestionably  the 


M/il^UFACTuRE  OF  GUNPOV/DER, 


395 


most  important  of  all  the  operations  in  the  manufacture  of 
gunpowder.  Without  it  there  Avould  he  no  manufacture,  for 
the  charge  of  saltpetre,  sulphur,  and  charcoal  goes  to  the  in- 
corating-mill a mere  mixture,  and  leaves  it  gunpowder,  l^oth- 
ing  that  can  he  done  to  it  afterwards  will  add  to  its  strength  or 
explosiveness ; no  future  treatment  can  remedy  defective  in- 
corporation. By  incorporation  is,  of  course,  meant  the  long- 
continued  grinding  together  of  the  ingredients  which  hlends 
them  together  and  brings  them  into  such  close  juxtaposition, 
that  they  appear  to  form  a new  substance.  Unless  this  be 
done  perfectly,  perfect  mutual  decomposition  of  the  con- 
stituents of  the  gunpowder  cannot  be  expected  on  combustion. 
The  more  thoroughly  it  is  effected,  the  stronger  will  be  the 
resulting  gunpowder. 

1104.  Upon  the  thorough  and  effectual  mcorporatiou  wliich 
it  receives  depends  mainly  the  excellence  of  powder.  Great 
attention  is  paid  to  the  process,  not  only  for  military,  but  for 
sporting  purposes,  and  the  most  powerful  mills  are  always 
used.  It  has  been  carried  to  the  highest  pitch  of  excellence, 
and  in  many  eases  it  is  carried  on  for  an  unnecessary  length  of 
time;  some  of  the  liner  sporting  powders  are  said  to  be  incor- 
porated for  twelve  hours.  Provided  the  iucorporating-mill  is 
sufficiently  powerfid,  and  is  worked  at  a sufficient  speed,  a 
most  thorough  incorporation  can  be  effected  in  a few  hours, 
after  which  there  is  no  object  in  continuing  the  process.  But 
as  imperfectly  incorporated  powder  cannot  fail  to  be  of  inferior 
(quality,  and  to  foul  the  gun  under  most  circumstances,  it  is 
best  to  incorporate  the  materials  as  thoroughly  as  possible ; and 
if  the  powder  is  thus  rendered  too  explosive,  this  quality  can 
be  reduced  by  increasing  its  density  and  hardness,  and  by  vary- 
ing the  shape  and  size  of  its  constituent  grains.  (Art.  1114.) 

1105.  Imperfect  Incorporation. — What  may  be  expected  of 
an  imperfectly  incorporated  powder  may  be  at  once  seen  by 
burning  small  quantities  of  different  powders,  varying  in  the 
amount  of  incorporation  they  have  undergone,  on  plates  of 
glass  or  porcelain.  A perfectly  made  powder  flashes  off,  leav- 
ing nothing  but  some  smoke-marks ; an  imperfectly  worked 
powder  will  coat  the  plate  with  specks  of  un decomposed  salt- 
petre. 'Y\x\^  flashing  test  is  a simple  and  effectual  way  of  ascer- 
taining the  amount  of  working  which  has  been  bestowed  on 
the  powder  in  the  mills,  and  is  the  only  safe  and  infallible  test 
of  incorporation.  This  test  must  be  performed  by  an  ex- 
perienced person,  and  no  powder  which  does  not  stand  it  can 
be  expected  to  shoot  either  strongly,  uniformly,  or  cleanly. 

1106.  -The  Incokpoeating-mill. — In  order  to  effect  a close 


396 


NAVAL  ORDNANCE  AND  GUNNERY. 


and  intimate  reunion  between  the  saltpetre,  the  sulphur,  and 
the  charcoal,  they  must  be  rolled  and  ground  together  for  a 


Fig.  260. — Incorporating-mill.  (Elevation), 

length  of  time ; and  the  gunpowder-maker  finds  the  most 
effectual  way  of  accomplisliing  this,  is  to  grind  the  materials 
together  under  heavy  edge-runners  of  stone  or  iron,  which  by 
their  motion — a compound  of  rolling  and  twisting — soon  work 
them  into  a homogeneous  mass. 

1107.  The  mill  generally  used  consists  of  apair  of  large,  heavy 
edge-runners  of  iron  or  stone,  which  revolve  on  a strong  circii- 


MANUFACTURE  OF  GUNPOWDER. 


397 


lar  bed,  the  bed  being,  of  course,  stone  for  the  stone,  and  iron 
for  the  iron  runners.  (Figs.  260  and  261.)  Tlie  runners  are  of 


various  sizes,  weighing  from  3 to  4 tons  each,  and  being  from  4 
to  7 feet  in  diameter.  Those  of  the  smaller  diameter  are  better 
than  the  larger,  as  the  latter  caiise  a greater  twist  on  the  bed, 
and  are  therefore  more  apt  to  cause  accident.  The  face  of  the 
runners  should  be  nearly  flat,  with  a slight  bevel  towards  the 
edge. 

1108.  The  runners  are  connected  by  a powerful  spindle  of 
wrought-iron,  which  rests  in  brass  bouches  placed  in  the  cross- 
head, so  as  to  allow  the  spindle  and  runners  to  rise  and  fall 
according  to  the  thickness  of  the  layer  of  material  on  the  bed. 
The  spindle  is  placed  in  the  cross-head,  so  as  to  bring  one  runner 
nearer  to  it  than  the  other,  and  therefore  cause  them  to  describe 
different  paths  when  in  motion. 

1109.  The  cross-head  is  flxed  on  a vertical  shaft,  on  which 
is  fixed,  underneath  the  flooring  of  the  mill,  a wheel  driven  by 


398 


NAVAL  ORDNANCE  AND  GUNNERY. 


a pinion  on  the  driving-shaft,  which  passes  underneath  the 
whole  group  of  mills,  By  this  arrangement  the  whole  of  the 


Fig.  2G3. — Incorporating'  MiU.  (Section.) 


machinery  is  kept  underneath,  and  out  of  reach  of  damage  from 
explosion.  The  cross-head  is  fitted  with  a bracket  on  each  side, 
to  carry  2.  plow ^ or  wedged-shaped  piece  of  wood  shod  with  felt 
and  leather,  which  travels  round  on  the  bed  immediately  in 


MANUFACTURE  OF  GUNPOWDER. 


399 


front  of  the  rnimers,  and  thus  keeps  the  composition  from 
working  away  from  them. 

The  bed  has  a curb  or  edge  round  the  outside,  formed  by  a 
sloping  rim  or  casing  fixed  all  round  it ; that  on  the  inside  is 
formed  by  the  circular  base  of  the  conical  socket,  down  which 
the  vertical  shaft  of  the  cross-head  passes.  Both  the  inside  and 
the  outside  curbs  have  gun-metal  rings  round  them  for  the 
plows  to  work  against.  Every  fitting  and  bolt  is  arranged  witii 
the  greatest  care,  so  as  neither  to  break  nor  become  loose  from 
the  jolting  of  the  mill,  and  thus  drop  into  the  charge. 

illO.  Tools  Used. — The  instruments  used  are  a wooden 
ral:e,  to  distribute  the  charge  over  the  bed ; a shaver,  or  flat 
board  on  the  end  of  a staff,  to  push  off  the  charge  from  the  bed 
occasionally ; a copper  chisel,  to  be  used  in  getting  the  charge 
off  the  bed  when  finished ; a brush  for  brushing  the  materials 
into  the  centre  of  the  bed ; a wooden  mallet,  to  break  up  any 
caked  powder  which  may  adhere  to  the  runners  or  bed ; and  a 
copper  watering-pot,  used  for  watering  the  charge. 

fill.  The  Operation. — The  charges,  which  have  been  care- 
fully sifted  in  order  to  avoid  the  possibility  of  foreign  matters 
- getting  into  the  mill-bed,  are  thrown  one  half  on  each  side  of 
the  bed,  and  distributed  evenly  over  it.  The  runners  are  then 
moved  round  a quarter  I’evolution,  and  the  piece  of  mill-cake 
left  under  them  from  the  former  charge  is  broken  off  and  dis- 
tributed over  the  fresh  charge. 

1112.  This  portion  of  mill-cake  is  of  course  finished  powder, 
and  quite  hard,  if  the  nmners  have  been  left  standing  on  it. 
It  is  broken  up  and  distributed  to  prevent  its  adhering  to  the 
bed  and  causing  too  much  friction.  The  runners  are  usually 
left  on  the  portion  of  powder  on  which  they  stop  when  the  in- 
corporation is  complete,  as  the  attempt  to  move  them  off  on  to 
a leather  placed  on  the  mill-bed  involves  the  risk  of  a portion  of 
the  runner  coming  down  in  contact  with  the  bed,  and  thereby 
igniting  some  of  the  powder-dust  with  which  every  crevice  is 
filled. 

1113.  Before  starting  the  mill  about  two  pints  of  pure 
water  are  sprinkled  over  the  charge.  The  runners  are  then 
started  at  a speed  of  about  eight  revolutions  a minute.  The 
millinan  does  not  remain  in  the  mill,  but  only  goes  in  from 
time  to  time  to  push  up  the  charge  from  the  bed  and  to  add  a 
little  more  water  according  to  the  state  of  the  charge.  From 
two  to  three  pints  are  generally  found  to  be  necessary  in  very 
damp  weather,  and  as  many  as  eight  or  ten  in  very  bright  days. 
The  watering  of  the  charge  is  left  to  the  millman’s  judgment. 

1114.  Time  Iteguired  for  Incorporation. — The  times  of  in- 


400 


NAVAL  ORDNANCE  AND  GUNNERY. 


corporation  vary  with  the  power  of  the  mills.  Thns,  cannon 
powder  requires  3|-  hours  working  under  stone  lumners  weigh- 
ing 3|-  tons,  and  making  7^  revolutions  a minute,  but  only "2^ 
under  iron  runners  of  4 tons,  making  8 revolutions  a minute. 
Small-arm  (dog-wood)  powders  require  5^  hours  in  the  former 
mills,  and  4 in  the  latter. 

Taking  about  50  lbs.  as  the  maximum  amount  which  it  is 
best  to  incorporate  at  one  time  imder  one  pair  of  runners,  it  is 
easy  to  calculate  the  capacity  of  a gunpowder  factory.  A cer- 
tain amount  of  work  can  be  obtained  from  them,  and  no  expe- 
dient can  produce  more ; no  extra  time  or  work  can  be  ex- 
pended on  the  process. 

1115.  The  powers  of  a gunpowder  factory  are  therefore 
known,  being  regulated  by  the  numbers  of  pairs  of  incorporating 
runners  which  it  possesses.  The  manufacture  of  gunpowder 
cannot  be  hastened,  and  even  if  it  could,  an  explosion  may 
happen  at  any  moment  which  may  cripple  a factory  for  the 
greater  part  of  a year,  so  that  an  extensive  store  of  gunpowder 
is  always  required  to  be  kept  on  hand  in  case  of  war. 

1116.  Mill-calce. — As  the  process  of  incorporation  ap- 
proaches completion,  the  charge  requires  to  he  carefully  watched, 
in  order  to  ensure  each  finished  charge  leaving  the  mill  in  as 
nearly  as  possible  the  same  state  as  regards  moisture.  The 
appearance  of  the  powder  when  finished  depends  mainly  on 
the  state  in  which  the  charges  leave  the  mill.  The  finished 
charge  usually  has  from  two  to  three  per  cent,  of  moisture.  If 
too  much  moisture  be  present  as  the  incoiq)oration  draws  to  a 
close,  the  charge  must  be  repeatedly  pushed  up  with  a shover  ; 
if  too  little,  some  more  must  be  added  from  the  watering-pot. 
The  color  of  the  charge  gives  a very  good  indication  of  the 
amount  of  moisture  present. 

1117.  When  the  process  is  finished,  the  charge,  now  known 
mill-calce — being  partly  in  the  state  of  soft  cake,  and  partly  of 

dust — is  scraped  and  swept  up  from  the  mill-bed,  placed  in  wood- 
en tubs,  and  transferred  to  the  charge-houss  to  await  inspection. 
If  the  charges  are  found  to  be  of  a proper  color  and  consistency, 
samples  from  each  are  taken,  which,  after  being  roughly  granu- 
lated by  hand,  and  dried,  are  flashed  on  a glass  plate  to  ascertain 
the  thoroughness  of  the  incoiq)oration  which  they  have  under- 
gone. This  flashing  is  more  a matter  of  form  than  anything 
else,  for  the  mill-cake  seldom  fails  to  give  satisfactory  results. 

1118.  Danger  of  Incorporation. — As  incoi-poration  is  the 
most  important  of  all  the  operations  in  the  manufacture  of  gun- 
powder, so  it  is  by  far  the  most  dangerous.  Accidents  in  the 
subsequent  processes,  where  large  quantities  of  powder  are  sub- 


MANUFACTURE  OF  GUNPOWDER. 


401 


Jeeted  to  treatment  at  one  time,  are  fortunately  rare  ; but  in  the 
incorporating-mills  tliey  may  be  expected  from  time  to  time. 
It  is  hardly  possible  it  can  be  otherwise,  considering  the  enormous 
friction  to  which  the  powder  is  subjected  in  them. 

1119.  Tlie  amount  of  water  added  to  the  charge  does  not  re- 
duce the  ingredients  to  a pasty  mass,  and  so  lessen  their  explosive- 
ness; on  the  contrary,  the  charge  when  it  approaches  comple- 
tion is  highly  explosive.  If  a large  amount  of  water  Avere 
added,  the  saltpetre  Avould  be  partly  dissolved,  and  all  the  in- 
corporation preAdously  etfected  would  be  undone. 

1120.  It  is  difficult  to  conjecture  how  accidents  do  happen, 
unless  it  be  from  the  charge  adhering  to  the  runners  and  leaving 
the  bed  bare,  in  which  case  the  friction  betAveen  the  runner  and 
the  bed  is  so  great  as  to  cause  a spark.  Of  course  the  more 
obvious  causes  of  accident,  such  as  some  foreign  body  falling 
into  the  bed,  are  not  alluded  to  here,  but  only  those  causes 
which  are  as  yet  unknown,  and  Avhich  no  amount  of  vigilance 
can  altogether  avert. 

1121.  Drencliing-apjyaratus. — Admitting,  therefore,  that 
occasional  explosions  in  the  incorporating-mills  are  inevitable, 
the  object  of  the  manufacturer  is  to  render  them  as  harmless  as 
possible.  As  the  mills  are  generally  built  in  groups,  an  explo- 
sion in  one,  is  very  apt  to  spread  amongst  all  the  others  round 
it.  To  prevent  this  a drenching-aj>j>aratu8  (Fig.  263),  is  erected 
over  each  pair  of  runners. 

1122.  The  apparatus  consists  of  a large  shutter  pivoted  on  a 
spindle,  which  runs  through  the  whole  group  of  mills.  To  this 
spindle  the  shutter  in  each  mill  is  attached,  and  the  spindle 
passes  through  bearings  in  the  partition-walls,  so  that  the  lifting 
of  the  shutter  lifts  all  the  others.  Balanced  on  the  pivot-edge 
of  the  shutter  is  a large  copper  vessel  full  of  water.  This  A-essel 
is  so  arranged  that  the  slightest  lift  of  the  shutter  capsizes  its 
contents  into  the  bed  of  the  mill  beneath  it. 

1123.  An  explosion  in  one  mill,  therefore,  lifts  the  shutter 
above  it  and  throws  down  the  water  into  the  mill-bed,  and 
though,  of  course,  too  late  to  do  any  good  in  the  mill  which  has 
exploded,  the  movement  of  the  shutter  turns  the  spindle  and 
drowns  the  charges  in  all  the  adjacent  mills,  and  thus  saves 
them  from  explosion.  This  drenching-apparatus  is  found  to 
answer  very  Avell. 

1124.  The  explosion  of  a green  charge  does  not,  in  some 
cases,  do  much  damage  to  the  structure  of  the  mill  or  the 
machinery ; that  of  a Avorked  charge  is  very  violent,  and  leaves 
generally  no  part  of  the  structure  standing.  Consequently  all 
mills  should  be  made  of  very  strong  framework,  covered  with 

26 


402 


NAVAL  ORDNANCE  AND  GUNNERY. 


light  hoards,  which  can  he  quickly  replaced  if  destroyed  hy  an 
explosion.  Fortunately  the  men  do  not  requme  to  he  always  in 


A.  — Cistern  made  of  copper  to  hold  40  {jallons. 

B.  — Vf  eight  made  of  cast-iron  to  balance  the  shutter. 

C.  — Shutter  made  of  wood.  When  lifted  by  an  explosion  relieves  the  foot 

of  the  cistern,  A,  causing  it  to  turn  over,  drenching  the  mill,  and  also 
turning  over  ail  the  cisterns  in  connection  with  the  shaft,  D,  which 
passes  through  the  .stufinng-box,  E,  it  being  built  in  the  walL 

F. — Couplings  connecting.the  shafts  on  both  sides  of  the  wall. 

the  mills ; on  the  contrary,  they  only  enter  them  from  time  to 
time  for  a minute  or  so — either  to  liquor  the  charge,  or  to  see 
that  all  is  going  on  well. 

1125.  PRESSING. — Gunpowder  leaves  the  incorporating- 
mill  partly  in  the  state  of  soft  cake,  partly  dust.  The  cake 
hardens  very  considerably,  if  allowed  to  stand  for  a few  days. 
In  this  form  it  would  be  unfit  for  use.  The  cake  may  be 
broken  up  into  grains,  but  such  grains  are  too  soft  to  stand  much 
handling  or  transport  without  crumbling  to  dust.  Powder 
made  from  mill-cake  will  always  be  found  to  be  dusty,  and  such 
powder  must  always  be  irregular  in  action.  It  will  also  be 
much  more  liable  to  absorb  moisture,  and  therefoi'e  to  cake  and 
become  lumpy. 

1126.  To  ensure  uniformity  and  good-keeping  qualities,  and 
freedom  from  dust,  powder  must  be  converted  into  firm  grains. 
This  is  done  by  compressing  the  soft  material  into  hard  masses 
by  pressure  alone,  and  then  crushing  up  these  masses  into  the 
description  of  grain  required.  The  object  of  ])ressing,  then,  is 


MAircrFACTUEE  OF  GIJXPOWDEE. 


403 


Fig.  264. — Press.  Elevation  and  section  showing  press  in  action. 

A. — Cylinder.  B. — Earn.  C. — Press-box. 

D. — Overhead-block.  E E. — Standard. 

dranlic  gunpowder-press  is  shown  in  Figs.  264  and  265.  The 


to  convert  the  soft  dusty  mass  of  ineorpotated  ingredients,  now 
gunpowder,  into  hard  cakes  of  the  particular  density  which  is 
found  to  give  the  best  results  when  the  powder  is  finished. 
After  the  cakes  are  formed  they  can  be  broken  up  by  various 
contrivances  into  grains  of  any  size,  all  of  which  will  have  a 
uniform  density  and  hardness,  and  which  can  be  freed  from 
dust,  and  glazed  and  polished  so  as  to  bear  handling  and  trans- 
port without  breaking  or  crumbling. 

1127.  Gunpowder  is  generally  pressed  in  layers  between 
plates  of  gun-metal  or  copper,  in  a hydraulic  press.  Screw- 
presses  are  sometimes  used,  and  there  are  different  ways  of 
placing  the  powder  in  the  presses  used.  The  best  results  are 
found  to  be  obtained  by  pressing  in  thin  layers. 

1128.  DESCEiPTion  of  Press. — A convenient  form  of  by- 


404 


NAVAL  ORDNANCE  AND  GUNNERY. 


press-box  Is  made  of  gun-metal,  lined  inside  and  out  -with  oak 
boards,  and  is  of  great  strength.  The  bottom  and  one  side  are 


Fig.  265 — Press.  Elevation  and  section  showing  press  partly  unloaded. 

permanently  attached  to  each  other.  The  other  three  sides  are 
liinged  to  the  bottom,  so  that  they  can  be  opened  out  to  facili- 
tate unloading.  When  closed  tbey  are  secured  with  short, 
coarse-threaded  screws  of  gun-metal.  The  box  has  two  project- 
ing gun-metal  claws,  which  hinge  on  to  a fixed  horizontal  rod 
of  the  same  metal,  so  that  the  box  can  be  turned  on  it,  on  the 
table  of  the  hydraulic  press,  when  filled  and  ready  for  pressing, 
or  outwards  when  it  has  to  be  unloaded. 

1129.  Loading  the  Press. — Being  first  turned  down  on  its 
side,  the  open  top  is  closed  temporarily  with  a piece  of  board 
which  is  fitted  to  it.  What  is  now  the  uppermost  side  is  un- 
covered and  raised,  and  the  other  two  sides  are  fastened  in  their 
places.  Gun-metal  racks  to  hold  the  press-plates,  having  per- 


MANUFACTURE  OF  GUNPOWDER. 


405 


pendiciilar  grooves  in  them  inch  apart,  are  then  slid  in  on 
each  side,  and  the  plates  being  put  in,  the  powder-meal  is  shov- 
elled in  and  falls  down  readily  between  the  plates  till  the  box  is 
full ; the  racks  are  then  drawn  out,  leaving  the  plates  free,  with 
layers  of  powder  between  them.  The  excess  of  powder  being 
carefully  swept  off  the  edge  of  the  box,  the  upper  side  is 
lowered  and  screwed  to  the  other  three ; an  overhead-block  and 
tackle  are  made  fast  to  the  gun-metal  eye  on  the  side  of  the 
box,  and  the  box  is  turned  over  on  the  press-table. 

1130.  The  box  now  stands  on  its  bottom,  and  the  temporary 
board  with  which  the  top  has  been  closed  dui'ing  charging  being 
lifted  off,  the  powder  and  plates  will  be  found  to  have  settled 
down  several  inches  by  their  own  weight.  The  vacant  space  at 
the  top  is  tilled  up  by  shovelling  in  a few  more  layers  of  meal, 
placing  a plate  by  hand  on  each  in  succession,  till  the  press-box 
is  full.  The  overhead-block,  which  exactly  fits  into  the  press- 
box,  is  now  run  into  its  place,  over  and  nearly  touching  the  con- 
tents of  the  box,  and  secured  there,  when  everything  is  ready  to 
apply  the  pressure  until  the  box  rises  to  a sufficient  height. 

1131.  Unloading  the  Press. — After  the  designated  pressure 
has  been  attained,  the  press-table,  carrying  the  press-box,  is  allowed 
to  descend.  The  pumps  are  in  another  building,  separated 
from  the  press-house  by  large  traverses,  and  here  the  workmen 
remain  while  the  pressure  is  being  applied.  The  workmen  now 
re-enter  the  press-house  and  proceed  to  unload  the  box.  The 
overhead-block  is  first  run  out  of  the  way,  and  the  block  and 
tackle  being  attached  to  the  box,  it  is  turned  over  on  its  side. 
The  fixing-screws  are  now  taken  out  of  their  sockets,  and  the 
three  hinged  sides  of  the  boxes  opened  out,  leaving  the  powder 
and  press-plates  standing  in  a solid  mass.  Each  plate,  with  a 
layer  of  hard  slate-like  cake  adhei’ing  to  it,  is  separated  from  the 
one  beneath  it,  and,  being  lifted  into  a wooden  bin,  gets  a few 
knocks  with  a wooden  mallet,  which  cause  the  cake  to  fall  off  in 
irregular  fragments,  which  are  broken  into  pieces  of  the  size  of 
a man’s  hand,  shovelled  into  tubs,  and  removed. 

1132.  Uniformity  of  Residts. — To  obtain  pressings  of  equal 
density,  equal  quantities  of  powder-meal  must  be  compressed 
equal  distances.  It  is  a matter  of  considerable  difficulty  to  en- 
sure, uniformity  of  results  in  pressing  powder.  It  is  of  the 
highest  importance  that  the  density  obtained  should  be  uniform, 
for  recent  experiments  have  proved  conclusively  that  the  quali- 
ties and  explosive  effect  of  gunpowder  are  materially  affected 
by  comparatively  slight  variations  in  density.  It  is  perfectly 
possible  to  manufacture  powder  of  uniform  density,  and  such 
powder  will  give  accurate  and  uniform  results,  both  as  regards 


406 


NAVAL  ORDNANCE  AND  GUNNERY. 


pressure  in  the  gun  and,  consequently,  velocity  imparted  to  the 
projectile.  The  density  of  powder  is  given  in  the  press  ; the 
importance  of  accuracy  in  pressing,  in  which  the  shooting 
qualities  of  powder  therefore  entirely,  or  at  least  mainly,  de- 
pend, is  evident. 

1133.  As  the  powder-meal  possesses  varying  degrees  of  elas- 
ticity and  resistance  to  pressure,  depending  to  a great  extent  on 
the  moisture  it  contains,  and,  as  far  as  can  be  judged  by  experi- 
ence, on  the  state  of  the  atmosphere  at  the  time,  equal  pressures 
will  not  always  have  equal  effects.  It  is  therefore  very  neces- 
sary to  have  all  the  conditions  made  as  nearly  as  possible  the 
same  in  each  experiment.  If  equal  quantities  of  meal  contain- 
ing equal  quantities  of  moisture  could  be  compressed  to  the 
same  amount  in  equal  times  and  under  the  same  atmospheric 
conditions,  then  there  is  little  doubt  that  tolerable  uniformity 
of  density  would  be  attainable.  But  it  must  be  always  a matter 
of  the  greatest  difficulty  to  fulfil  all  these  conditions  exactly. 
In  the  ffi’st  place,  the  moisture  in  the  powder-meal  depends 
mainly  on  the  amount  of  liquoring  the  charges  have  received. 
This  is  usually  left  to  the  judgment  of  the  workman,  who  is 

“guided  by  the  state  of  weather.  And  though  the  charges  may 
be  unifomi  as  regards  moisture,  on  leaving  the  mills,  it  is  obvi- 
ous that  variations  of  temperature  between  the  days  of  incorpor- 
ation and  pressing  will  affect  them  unequally.  In  the  next 
place,  the  bulk  of  the  meal  is  affected  by  the  moisture  contained 
in  it,  so  that  fill  the  press-box  as  carefully  as  we  can,  we  do  not 
get  equal  quantities  to  be  subjected  to  pressure  each  time. 

1134.  If  the  quantities  operated  on  were  very  small,  it  might 
be  possible  to  devise  some  method  of  equalizing  the  moisture 
contained  in  them  ; but  when  large  charges  are  required  to  fill 
the  press-box,  it  becomes  a much  more  difficult  matter.  It  is 
necessary,  when  examining  the  densities  of  press-cake  in  order 
to  ascertain  if  it  is  fitted  for  the  manufacture  of  a particular 
])owder,  to  have  it  previously  dried. 

1135.  It  is  found  in  practice  that  though  absolute  uniform- 
ity cannot  be  guaranteed  in  pressing,  very  close  results  can  be 
obtained.  To  attain  absolute  uniformity  in  the  finished  pow- 
der, the  density  of  every  pressing,  after  it  has  been  converted 
into  grain,  is  taken,  and  the  different  pressings  are  then  mixed 
in  the  proportions  to  give  the  density  required.  Thus  if  the 
density  fixed  for  the  powder  be  1.07,  and  the  densities  of  the 
pressings  be  found  to  be  1.70  and  1.04,  they  would  be  mixed  iu 
equal  proportions,  and  would  give  a powder  of  1.67  density. 
Powders  which  differ  to  a great  extent  in  density  are  never 
mixed. 


MANTJFACTUEE  OF  GUFTPOVtTDER. 


407 


1136.  GRAINI?7G. — The  press-cake  must  now  be  converted 
into  the  particular  size  of  grain  required.  And  the  means  em- 
ployed to  break  uja  the  press-cake  must  be  so  arranged  as  to 
crush  it  up  as  nearly  as  possible  into  the  size  or  sizes  of  grain 
wanted,  without  reducing  much  of  it  to  dust.  The  smaller  the 
size  of  grain,  the  larger  will  be  the  percentage  of  it  obtained 
from  granulated  press-cake ; hence  with  the  small  size  of  grain 
formerly  used  with  cannon,  any  of  the  older  and  ruder  appli- 
ances for  effecting  granulation  gave  good  percentage  of  grain. 
But  as  recent  experiments  have  conclusively  proved  that  much 
larger-sized  grains  should  be  employed  in  large  charges  for 
heavy  ordnance,  new  and  improved  granulating-machines 
have  been  introduced.  Large  powders  have  been  made  by 
tlirowing  the  press-cake  on  a table  and  breaking  it  up  by  hand 
with  mallets ; but  there  is  little  doubt  that  arrangements  and 
alterations  can  be  made  in  the  machines  so  as  to  enable  them  to 
granulate  powders  of  any  size  of  grain. 

1137.  Geanulating-machine. — The  granulation  is  effected 
by  passing  the  press-cake  between  revolving  toothed  rollers  of 
gun-metal.  The  machine  contains  four  pairs  of  such  rollers  ar- 
ranged in  a slanting  direction,  one  above  the  other.  (Fig.  266.) 


A.  — Hopper  witli  raising  arrangement.  EE. — Long  Screen. 

B.  — Endless  Band.  F. — Box  for  Dust. 

CCCC. — The  4 pairs  of  Rollers.  G. — Box  for  Grain. 

EBB. — The  Short  Screens.  H. — Box  for  “ Chucks.” 

These  rollers  are  set  in  the  two  strong  side-frames  of  gam- 
metal  which  form  the  framework  of  the  machine.  Each 
]>air  is  adjusted  at  the  proper  distance  apart  by  set-screws;  but 
the  back  roller  of  each  pair  works  in  a sliding  bearing,  which  is 
kept  up  against  the  bearing  of  the  other  roller  by  a weighted 
lever,  so  as  to  admit  of  the  rollers  opening  out  and  admitting 
an  excess  of  material  to  pass  through  without  injury  to  the  ma- 


40S 


NAVAL  ORDNANCE  AND  GUNNERY. 


chine.  The  two  upper  pairs  of  rollers  have  coarser  teeth  than 
the  lower  pairs. 

1138.  Slanting  rectangular  sieves  or  screens  are  placed  un- 
derneath each  of  the  three  upper  pairs  of  rollers  to  the  top  of 
the  next,  to  convey  any  fragments  which  escape  proper  crashing 
in  one  pair  into  the  teeth  of  the  next  pair.  Underneath  the 
whole  is  a long  rectangular  frame  carrying  two  long  screens  to 
separate  the  proper  size  of  powder,  and  a board  underneath  to 
receive  the  dust  and  carry  it  down  into  a tub  placed  to  receive 
it.  Both  the  short  screens  and  the  long  frame  are  attached  to 
the  framework  of  the  machine,  and  receive  a vibratory  motion 
by  means  of  appro j)ri ate  mechanism. 

1139.  Attention  must  be  paid  to  the  angles  at  which  the 
different  screens  are  placed  ; this  varies  in  different  machines, 
and  the  proper  inclination  can  only  be  ascertained  by  experi- 
ment. These  screens  will  of  course  require  to  be  changed  for 
each  different  size  of  powder  that  is  being  made. 

1140.  Action  of  the  Machine. — The  general  action  of  the 
machine  will  be  understood  from  Fig.  266.  The  press-cake  is 
placed  in  a hopper  at  the  back  of  the  machine,  and  earned  up 
by  means  of  an  endless  band  of  canvas  having  strips  of  leather 
sewed  to  it  to  catch  the  cake.  The  band  passes  under  a scraper 
which  prevents  too  much  cake  being  carried  up  at  once.  The 
cake  falls  between  the  first  pair  of  rollers,  which  work  at  a 
speed  of  about  thirty  revolutions  per  minute,  and  is  immediately 
crashed  up  into  granular  fragments  which  fall  in  the  first  short 
screen.  The  whole  of  the  grains,  except  the  fragments  which 
are  too  large,  fall  through  this  screen  directly  on  to  the  surface 
of  the  upper  long  screen  underneath,  and  fall  through  it  like- 
wise to  the  second,  Avhich  permits  the  dust  and  minuter  parti- 
cles to  fail  through  on  to  the  sloping  board  underneath,  down 
which  they  slide  into  the  tub  placed  to  receive  them,  but  Avhich 
retains  the  proper  size  of  grain,  which  in  turn  rolls  down  it  mto 
another  receptacle  at  the  bottom. 

1141.  The  larger  pieces  Avhich  escaped  proper  crushing  in 
the  first  pair  of  rollers  are  shaken  down  by  the  first  short  screen 
into  the  second  pair,  to  undergo  the  same  process  as  at  first,  and 
so  on  Avith  the  third  and  fourth  pairs  of  rollers.  Some  fi*ag- 
ments  of  too  coarse  a size  Avill  escape  all  the  rollers,  and  conse- 
quently require  a third  box  to  receive  them  in  front  of  the  other 
two  placed  to  receive  the  dust  and  grain  respectively.  These 
pieces,  termed  chuchs,  require  to  be  passed  through  the  machine 
again. 

1142.  TFhen  the  hopper  has  reached  the  limit  of  its  travel 
upAvards,  and  all  the  cake  has  fallen  out  into  the  band  and  been 


MAyUFACTIJEE  OF  GUNPOWDER. 


409 


conveyed  up  to  the  machine,  a clutch  is  relieved  which  stops 
the  upward  travel  of  the  hopper,  and  a hell  is  rung  in  the  watch- 
house  where  the  workmen  remain  during  the  time  the  machine 
is  working.  The  machine,  being  self-supplying,  requires  no 
watching  when  working.  As  soon  as  the  bell  rings  the  work- 
men re-enter  the  house  and  place  tlie  grain  and  dust  in  tubs 
ready  for  transmission  to  the  proper  store-rooms. 

1143.  Danger  of  the  Process. — To  judge  from  the  large 
proportion  of  accidents  which  take  place  in  granulating-houses, 
the  process-would  appear  to  be  specially  dangerous.  It  is  diffi- 
cult to  account  for  the  fatality  which  accompanies  granulating- 
houses.  In  any  well-regulated  factory  the  operation  is  not  con- 
sidered to  be  any  more  dangerous  than  any  of  the  other  pro- 
cesses, but  statistics  show  beyond  doubt  that  it  must  be  specially 
dangerous.  The  probable  explanation  appears  to  be  that  if 
there  has  been  any  negligence  anywhere  in  keeping  fragments 
of  foreign  matter  from  the  powder  as  it  progresses  through  the 
various  stages  of  manufacture,  the  granulating-house,  in  which 
the  powder  undergoes  more  crushing  and  grinding  than  it  does 
anywhere  else,  anrl  where  there  are  a number  of  metal  axles  and 
bearings  at  work,  is  the  place  where  such  negligence  will  most 
surely  tell. 

1144.  Dusting  AND  Glazing. — The  granulated  powder  as  it 
comes  from  the  machine  contains  amongst  it  a large  cpiantity  of 
dust.  This  is  formed  by  the  crushing  action  of  the  granulating 
machine,  and  must  of  course  pass  through  the  various  sieves 
and  screens  with  which  the  machine  is  provided  along  with  the 
grain.  The  grain  itself  is  not  in  a condition  to  be  made  use  of 
as  powder,  being  rough  and  porous  on  the  surface  and  very  an- 
gular in  shape ; and  moreover,  the  presence  of  a large  quantity 
of  fine  dust  amongst  it  would  render  it  not  only  most  incon- 
venient to  handle,  but  would  also  render  it  more  liable  to  absorb 
moisture,  and  to  deteriorate. 

1145.  A rough,  unpolished  angular  grain  would  also  very 
speedily  rub  down  into  dust,  if  subjected  to  much  shaking  in 
transport.  It  becomes  necessary,  therefore,  to  free  the  granu- 
lated powder  from  all  traces  of  dust,  and  to  polish  or  give  a sur- 
face to  the  grains  themselves  to  enable  them  to  bear  a great 
deal  of  friction  without  deterioration. 

1146.  Powder  is  freed  from  dust  by  placing  it  in  revolving 
reels  covered  with  cloth  or  wire  mesh  of  various  degrees  of 
fineness,  through  which  the  dust  escapes.  It  is  glazed  by  caus- 
ing the  grains  to  rub  against  each  other  in  revolving  wooden 
barrels.  The  extent  to  which  the  operations  of  dusting  and 
glazing  are  carried,  and  the  nature  of  the  appliances  used,  de- 


410 


NAVAL  ORDNANCE  AND  GUNNERY. 


pend  entirely  on  the  density,  hardness,  and  size  of  grain  of  the 
powder  operated  on. 

1147.  Large-grained,  dense,  hard  powder  will  hear  a great 
deal  of  knocking  abont  in  tire  reels  without  becoming  disinte- 
grated and  forming  fresh  dust;  and  will,  moreover,  bearagi’eat 
deal  of  friction  in  the  glazing  barrels,  acquiring  speedily  a high 
degree  of  polish.  But  when  operating  on  a small-grained,  soft 
powder  of  low  density,  the  dusting  must  be  carefully  conducted, 
as  the  process  will  develop  as  much  fresh  dust  as  it  removes; 
and  the  amount  of  friction  the  grains  will  bear  in  glazing  must 
be  likewise  carefully  regulated. 

11-18.  It  is  found  in  practice  that  powder  may  be  divided 
into  two  general  classes,  each  of  which  requires  different  treat- 
ment in  dusting  and  glazing,  viz.,  the  cannon  jpovcd^cr  of  all 
(‘lasses,  and  the  small-arm  powder  of  all  classes.  The  former 
is  not  only  pressed  to  a higher  density,  but  is  made  of  a larger 
size  of  grain  ; the  latter  generally  is  of  lower  density  and  much 
smaller  size. 

Modern  cannon  powder,  being  of  large-sized  grains  and  of 
firm  consistency,  admits  of  a comparatively  open-ineshed  reel- 
covering being  used  in  dusting,  and  of  the  process  being  contin- 
ued as  long  as  required  without  risk  of  injury  to  the  grain. 
The  powder  can  therefore  be  rendered  perfectly  free  from  dust, 
and  sufficiently  glazed  at  the  same  time,  coming  out  of  the  reel 
as  finished  powder  at  one  operation. 

1140.  The  Dusting-eeel. — There  are  two  classes  of  reels 
in  use,  the  horizontal  and  the  slope,  the  former  usually  employed 
with  j:)owder  of  large  grain,  and  the  latter  with  fine-grain  pow- 
der. Different  powders  take  different  lengths  of  time  to  be 
freed  from  dust,  and  require  different  descriptions  of  reel-cover- 
ings. It  is  impossible,  therefore,  to  lay  down  exact  rules  in 
such  matters,  and  it  would  be  tedious  to  go  over  all  the  particu- 
lars of  the  numerous  dustings  that  all  kinds  of  powders  undergo. 

1150.  A horizontal  reel  (Fig.  2GT),  consists  of  a cylindrical 
skeleton  of  wooden  hoops  supported  on  a shaft  by  radial  arras, 
the  skeleton  being  covered  with  canvas  or  wire  cloth.  The 
reels  are  made  in  Mves  for  convenience  of  repair  and  re-cover- 
ing. The  shaft  is  of  iron,  covered  with  wood ; the  radial  arms 
are  of  gun-metal ; the  ends  are  formed  of  two  short  disks  of 
wood  screwed  upon  the  shaft.  One  end  can  be  unscrewed  and 
drawn  back.  The  bearing  of  the  reel-shaft  next  this  movable 
end  is  fixed  in  a block  which  can  be  lowered  if  necessary,  so  as 
to  put  the  reel  for  the  time  being  on  a slope.  In  the  middle  of 
the  reel  is  a square  opening  closed  with  a wooden  door,  through 
which  the  powder  is  placed  in  the  reel,  being  run  through  a 


MAlSrCTFACTURE  OF  GUNPOWDER, 


411 


hopper  at  the  top  of  the  parallel  wood-casing  in  which  the  reel 
is  placed  to  coniine  the  dust  which  escapes  from  it. 


Fig.  267. — Ilorizontal  Reel.  (Section.) 

AA.— Reel  Covering.  D.— Opening  for  loading. 

B.— Shaft.  E.— Hopper  for  loading. 

CO.— Movable  End.  FF.— Reel  Case. 

G.— Block  carrying  the  bearing  of  the  lower  end,  which  can  he  raised  or 
lowered  by  means  of  the  rope,  K,  and  Lever,  L. 

1151.  Horizontal  re^ls  are  intended  to  receive  a quantity 
of  powder  for  a certain  length  of  time,  and  to  revolve  with  it, 
shaking  it  against  the  reel  covering,  and  thus  forcing  the  dust 
through  the  meshes,  When  a reel  has  run  the  required  time, 
say  a half-hour,  making  forty  revolutions,  with  a charge  of 
powder,  the  driving-wheel  is  made  to  revolve  very  slowly,  the 
end  of  the  reel  is  lowered  by  means  of  a rope  and  lever,  and 
the  movable  end  of  the  reel  is  unscrewed  and  drawn  back.  As 
the  reel  slowly  revolves  the  powder  runs  out  into  a hopper  and 
is  conducted  into  the  baiTels. 

1152.  Slope  reels  are  not  intended  to  retain  the  powder, 
but  only  to  extract  a certain  portion  of  dust  as  it  runs  through 
them.  They  resemble  the  horizontal  reels  in  general  construc- 
tion, except  they  have  no  ends  and  the  shaft  is  set  at  a perma- 
nent slope.  Each  reel  is  provided  with  a feeding-hopper  at  its 
upper  end ; attached  to  which  is  a loose  spout  for  guiding  the 
powder  into  the  reel. 

1153.  The  Glazing-barkel. — Glazing-barrels  consist  of 


412 


NAVAL  ORDNANCE  AND  GUNNERY. 


large  strong  wooden  baiTels  (Fig.  268)  supported  on  an  iron 
shaft  Avhich  runs  through  their  centre.  The  barrels,  tAvo  of 


which  are  generally  placed  in  line  on  one  shaft,  are  made  of 
oak,  and  are  aboiAt  5 feet  long  and  2|-  in  diameter ; the  shaft  is 
eased  with  wood  where  it  passes  through  the  barrels.  Each 
barrel  is  provided  with  a small  square  door  for  charging  and 
uncharging. 

1154.  The  barrels  are  found  to  be  peculiarly  well  adapted 
for  the  purpose,  oAving  to  their  shape.  Formerly  wooden  cylin- 
ders with  straight  sides  were  used,  but  it  was  found  that  the 
ditferent  sizes  of  grain  had  a tendency  to  separate  in  them,  so 
that  all  did  not  receiA^e  an  equal  amount  of  polishing.  But  in 
the  barrels,  which  are  larger  in  diameter  at  the  centre,  there  fs 
a constant  intermingling  of  the  grain  and  a more  uniform 
action. 

1155.  With  large-grained  powders  sometimes  a little 
graphite  is  used  to  obtain  a better  surface.  This  gives  a line 
silvery  surface  to  the  grain,  but  care  must  be  taken  to  use  the 
proper  description  of  black  lead.  This  is  really  an  impurity, 
and  should  therefore  be  sparingly  supplied  to  powder.  It  is 
never  used  Avith  any  of  the  fine  small-arm  powders,  but  only 
with  poAA'ders  intended  to  be  used  in  large  charges  and  Avith  the 
express  intention  of  giving  them  a surface  which  will,  if  any- 
thing, retard  rather  than  quicken  ignition.  Inferior  blasting- 
poAvder  is  sometimes  polished  in  this  way  to  a high  degree  of 
brilliancy,  but  the  lustre  is  no  test  of  its  quality. 

1156.  The  friction  of  the  grains  in  the  glazing-bai’rels 


MAOTJFACTUKE  OF  GUNPOWDER. 


413 


necessarily  generates  a good  deal  of  heat.  Some  of  the  fine- 
grain  powders  which  require  a long  time  in  glazing  come 
out  so  hot  as  hardly  to  admit  of  the  hand  being  plunged  in 
them.  In  all  cases  the  heat  generated  is  so  great  as  to  cause 
the  powder  to  part  with  almost  all  its  moisture  ; but  as  there 
is  little  or  no  escape  for  it,  it  condenses  on  the  interior  of  the 
barrels  and  forms  a hard  coating  with  the  powder-dust.* 

1157.  The  glazing  process  not  only  polishes  the  grains,  but 
tends  to  rub  off  their  more  prominent  angles  and  to  bring  them 
to  a rounded  form.  It  generates  a little  dust,  and  requires, 
therefore,  a second  dusting,  after  which  it  has  only  to  be  dried 
to  be  ready  for  use. 

1158.  Drying. — The  drying-rooms  consist  of  large  cham- 
bers having  an  arrangement  of  steam-pipes  running  along  the 
floor,  and  provided  with  double  doors  which  can  be  closely 
shut,  and  with  ventilators  at  top  and  bottom  which  can  be 
closed  or  opened  from  without.  The  temperature  is  main- 
tained at  from  125°  to  130°  F.,  and  regulated  by  a large  ther- 
mometer inside,  which  can  be  read  from  without. 

The  chambers  are  fitted  with  wooden  racks,  on  which  are 
placed  the  trays  containing  the  powder.  The  powder  is  gener- 
ally kept  one  day  in  the  drying-room.  In  the  case  of  large- 
grain  powder,  wFen  withdrawn  it  is  placed  in  barrels  and 
headed  up  for  issue.  But  in  the  case  of  fine-grain  powders,  a 
third  dusting  is  sometimes  requisite  to  remove  all  traces  of  dust 
and  fit  them  for  service.  This  is  teYmed  Jmishing,  and  is  done 
in  a horizontal  reel. 

Explosions  of  drying-rooms  are  comparatively  rare. 

1159.  Special  Powders. — On  the  introduction  of  the 
mammoth  modern  ordnance  it  became  apparent  that  the  ordi- 
nary powders  in  use  were  too  sudden  in  their  action  for  the 
power  of  the  guns.  This  led  to  the  making  of  special  powders 
in  the  shape  of  prisms,  cylindrical  pellets,  spheres,  etc.,  with  a 
view  of  modifying  the  explosiveness  of  the  charges. 

1160.  Large-grain  powder  for  heavy  guns  was  first  adopted 
in  this  country  in  1861,  at  a time  when  other  nations  continued 
the  use  of  small-grain.  This  great  improvement  in  the  mode 
of  manufacture  was  the  result  of  careful  study  and  experiment. 
The  invention  of  Hodman’s  “ perforated  cake,”  or  prismatic 
powder,  which  has  been  adopted  by,  and  is  now  in  use  in  both 
Russia  and  Germany,  and  the  “ pebble  ” powder,  similar  to 
our  “mammoth,”  adopted  by  England,  created  that  revolution 
in  the  manufacture  of  gunpowder,  based  upon  purely  scientific 

* Glazing  barrels  are  now  fitted  with  ventilating  bungs  which  open  at  each 
revolution,  and  aUow  the  heated  air,  surcharged  with  moisture,  to  escape ; 
thus  preventing  ‘‘  sweating.” 


NAVAL  OKDNANCE  AND  GUNNEET. 


il4 

principles  of  combustion  and  evolution  of  gases,  that  has  ena- 
bled all  nations  to  increase  the  size  of  their  ordnance. 

The  question  of  variations  of  the  density  of  powder  and  of 
the  effect  whieli  such,  especially  when  combined  with  variations 
in  shape  and  size  of  grain,  could  not  fail  to  produce,  soon  began 
to  attract  general  attention.  Those  who  studied  the  subject 
soon  became  aware  of  the  immense  advantage  to  be  derived, 
not  only  from  increasing  the  density  of  powder,  and  thereby 
lessening  e.xplosiveness  and  consequent  strain  on  the  gun,  hut 
from  uniformity  of  density  and  shape  of  grain  as  affecting  reg- 
ularity of  effect. 

IIGI.  Experiments  are  still  being  made  with  a view  of  de- 
termining the  description  of  gunpowder  whose  employment  in 
large  charges  is  attended  with  the  least  risk  of  overstraining  the 
heavy  gnns  in  service. 

The  projecting  charge  should  be  so  related,  in  its  rate  of 
combustion  to  the  form  of  the  gun  from  which  it  is  fired,  that, 
with  a given  convenient  thickness  of  metal  and  length  of  bore, 
the  maximum  velocity  of  projectile  attainable  from  such  gan 
should  be  produced. 

In  comparing  one  gunpowder  with  another,  the  radical 
question  is,  which  contains  the  best  supply  of  gases,  and  which 
maintains  this  supply  most  advantageously  at  the  required  ten- 
sion. The  tension  may  be  too  low  as  well  as  too  high  ; what 
is  wanted  is  an  elastic  force  which  will  not  strain  the  gun  more 
than  is  needed  to  give  to  the  projectile  the  required  terminal 
speed. 

The  causes  which  affect  the  quality  and  character  of  gun- 
powder, and  the  phenomenon  which  attends  its  application  to 
projectile  purposes,  depend  upon  the  concurrence  of  a variety 
of  conditions,  not  a few  of  which  are  unknown. 

Ill  powder-making,  ability  to  reproduce  results  will  always 
be  the  important  question ; so  many  disturbing  causes  tend  to 
affect  its  final  qualities  that,  after  every  precaution  has  been 
taken  to  remove  them,  perfect  uniformity  in  the  finished  arti- 
cle produced  from  day  to  day  cannot,  with  our  present  means 
and  knowledge,  be  surely  counted  upon. 

1162.  TERMS  APPLIED  TO  DIFFEREXT  KIXDS 
OF  POWDER. — Dunpowder  for  the  Xaval  Service  is  known 
and  designated  under  the  following  heads : Hexagonal,  Mam- 
moth, Rflle,  Cannon,  Shell,  and  Small-arm  ; classed  according  to 
the  size  of  the  grain.  They  are  all,  as  a general  rule,  made  of 
the  same  proportion  of  ingredients,  although  the  size  and  den- 
sity of  the  grains,  hardness,  and  amount  of  glazing  is  different 
with  each. 


MANUFACTURE  OF  GUNPOWDER. 


415 


PLAN 

•0  ■ a-— 


These  points  are  now  being  experimented  on,  and  change 
of  classification  about  to  be  made. 

1163.  Majoiotii  Powder. — This  is  an  irregular,  large- 
grained  powder  about  0.8  inch  in  diameter,  which  is  used  for 
large  charges  in  heavy  guns. 

The  large-grain  powder  greatly  diminishes  the  strain  on 
the  gun,  in  producing  a given  velocity,  from  that  due  to  ordi- 
nary cannon  powder,  because  of  the  longer  time  required  for 
the  complete  combustion  of  each  grain.  The  larger  the  grain, 
other  things  being  equal,  the  less  v/ill  the  maximum  exceed 
the  mean  pressure,  and  the  greater  will  be  the  charge  required 
to  produce  a given  velocity. 

1164.  Prismatic  Powder,  or  perforated  cake-powder  (Fig. 
269.) — This  is  ordinary  powder  made  in  the  form  of  regular 
hexagonal  prisms  about  one  inch 
thick  and  0.8  inch  in  the  side, 
perforated  with  seven  holes  about 
0.1  inch  in  diameter. 

The  cakes  are  formed  by  plac- 
ing mealed  powder,  moistened 
sutficiently  with  water,  in  a mold 
of  the  proper  form,  and  subject- 
ing it  to  the  required  pressure. 

In  making  up  charges  of  this 
powder  the  prisms  are  built  up 
regularly  in  the  cartridge-bags 
like  honeycomb,  which  are  then 
tightly  tied  at  the  mouth,  so 
that  the  grains  are  kept  in  place. 

These  perforations  thus  form  long 
tubes  through  the  charge,  b,7 
which  the  gas  permeates  the 
whole  mass. 

This  powder,  originally  from 
the  United  States,  has  been  in- 
troduced into  the  German,  Rus- 
sian, and  Austrian  services,  and 
finds  many  advocates  elsewhere. 

This  form  of  powder  is  based  on  the  theory  that  the  grains, 
being  ignited  through  the  perforations,  burn  outwardly,  pro- 
ducing a progressively  increasing  surface  of  ignition,  thereby 
evolving  greater  volumes  of  gas,  as  the  velocity  of  the  projec- 
tile is  increased,  and  the  space  through  which  the  gas  develops 
is  augmented. 

1165.  Hexagojxal,  Powder. — This  powder,  represented  in 


ELEVATION 


Fig.  2G9. 


4:16 


NAVAL  ORDNANCE  AND  GUNNERY. 


Fig.  270,  is  about  0.7  inch  in  diameter,  and  made  by  Dupont 
& Co.  It  has  lately  been  introduced,  and 
has  given  very  good  results.  The  granula- 
tion is  veiy  unifonn.  It  is  called  “ Hex- 
agonal ” by  the  manufacturers  probably  be- 
cause it  is  nearly  so  in  cross-section. 

1166.  Waffle  Powder. — This  powder 
proposed  by  Commodore  Jeffers,  has  been 
experimented  with  to  some  extent  in  the 
navy,  with  excellent  results.  It  is  pressed  between  plates  with 
projecting  ribs  similar  to  “ waffle-irons,”  which 
furnish  a simple  means  of  obtaining  regular 
granulation,  and  thus  controlling  tlie  sur- 
face. The  fracture  of  the  press-cake  takes 
place  along  the  grooves  thus  formed,  dividing 


the  cakes  into  squares,  or  rather  truncated 


Fig.  270. 


its  resemblance 
powder,  similar 


pyramids,  precisely  as  in  Fig.  271,  and  of 
about  the  same  general  size  as  the  hexagonal 
powder. 

1167.  Pebble  Powder — so  called  from 
to  small  black  pebbles.  This  is  an  English 
to  onr  Mammoth  powder.  It  consists  of 


irregular  cubes,  having  edges  from  five-eighths  to  four-eighths 
inch  in  length,  made  by  cutting  up  the  press-cake  into  the  re- 
quired form. 

1168.  Pellet  Powder. — This  is  an  English  term  applied 
to  a large-grained  powder.  The  pieces  of  the 

, Pellet  powder  are  all  of  uniform  size  and  cylin- 

drical  shape,  about  one-half  inch  long  and 

three-c[uarter  inch  diameter,  with  a perfora- 
tion at  one  end  to  give  greater  igniting  siu- 
face.  (Fig.  272.) 

1169.  lIiFLE  Large  Gralx  powder,  or  ‘‘K. 
L.  G.”  powder,  is  an  English  service  powder, 
in  grains  which  pass  through  a sieve  of  four 
meshes,  but  are  retained  in  one  of  eight  meshes 
to  the  inch. 

1170.  Macheves  for  Maxixg  Special  Pow- 
ders.— The  fundamental  parts  of  every  ma- 
chine, for  making  this  class  of  powder,  are: 
1st,  a mold  in  which  to  place  the  powder-mer.l ; 
2d,  a punch  accurately  fitting  the  mold,  Avith 
which  to  compress  the  poAvder ; 3d,  some  appli- 
ance for  pressing  the  finished  pellets  out  of  the 
molds. 


Fig.  272. 


MANUFACTURE  OF  GUNPOAVDER.  417 

1171.  A safe  arrangement  for  combining  these  three  is 
sho’wn  in  Fig.  273.  A is  a small  charge  of  powder  placed  in 


the  mold,  B,  which,  fits  it  accuratelj.  This  punch  has  a shoul- 
der on  it  on  which  it  rests  loose  on  a second  plate,  C,  under- 
neath the  mold-plate.  The  lower  end  of  this  pundi  rests  on 
the  upper  surface  of  the  hydraulic  ram,  D.  An  upper  descend- 
ing punch,  E,  of  larger  diameter  than  the  mold,  can  be  brought 
27 


418 


NAVAL  OKDXANCE  AND  GUNNERY. 


down  to  the  surface  of  the  mold-plate  either  bj  a screw  or  by 
a hydraulic  pressure,  so  as  to  close  the  mold. 

With  siich  an  arrangement  a pellet  can  he  safely  made, 
firstly,  by  bringing  the  top  punch  down  on  the  plate  and  fixing 
it  there  so  as  to  confine  the  povrder ; secondly,  by  raising  the 
lower  punch,  by  means  of  the  ram,  till  a proper  amount  of 
compression  has  been  given  to  the  powder ; thirdly,  by  stop- 
ping the  ])ressure  from  beneath  and  raising  the  upper  punch ; 
and,  fourthly,  by  raising  the  finished  pellet  out  of  the  mold  by 
the  pressure  of  the  ram  underneath. 

1172.  It  is  plain  that  any  form  caii  be  given  to  the  pellets 
by  altering  the  shape  of  the  molds  and  punches,  and  that  hob 
lows  or  perforations  can  be  made  in  the  pellet  if  recpiired. 
There  is  no  difiei'ence  really  in  any  of  these  jmwders.  except  in 
the  shape.  A machine  exactly  similar  to  this  could  be  used 
for  making  powder  into  hexagonal  prisms  perforated  with 
holes.  However,  machines  of  different  descriptions  are  em- 
ployed in  different  countries  and  by  different  makers.  ATiat- 
ever  arrangement  is  used,  it  must  be  always  remembered  that 
the  only  safe  Avay  of  ensuring  tolerable  uniformity  of  density 
is  to  compress  a certain  amount  of  meal  into  a certain  space ; 
and  that  giving  each  pellet  the  same  amount  of  pressure  in 
|)ounds  does  not  necessarily  turn  out  powder  of  uniform 
density. 

1173.  EXPLOSION. — The  phenomenon  of  explosion  of 
gunpowder  may  be  divided  into  three  parts,  viz. : ignition,  in- 
jiammatiov , and  combustion. 

By  ignition  is  luiderstood  the  setting  on  fire  of  a particular 
part  of  the  charge;  by  inflammation,  the  spread  of  ignition  from 
grain  to  grain  ; and  by  combustion,  the  burning  of  each  grain 
from  its  surface  to  centre. 

1174.  Ignitiox.— Gunpowder  may  be  ignited  by  the  electric 
spark,  by  contact  with  an  ignited  body,  or  by  a sudden  heat  of 
572°  F. ' A gradual  heat  decomposes  powder  without  explosion, 
by  subliming  the  sulphur.  Flame  will  not  ignite  gunpowder 
unless  it  remains  long  enough  in  contact  with  the  grains  to  heat 
them  to  redness.  Thus  the  flame  from  burning  paper  may  be 
touched  to  grains  of  powder  without  igniting  them,  owing  to  the 
slight  intensity  of  the  flame  and  the  cooling  effect  of  the  grains. 

" 1175.  It  inay  be  ignited  by  friction,  or  a shock  between  two 
solid  bodies,  even  when  they  are  not  very  hard.  Experiments 
show  that  gunpowder  may  be  ignited  by  the  shock  of  copper 
against  copper,  copper  against  iron,  lead  against  lead,  and  even 
lead  against  wood ; in  handling  gunpowder,  therefore,  violent 
shocks  between  all  solid  bodies  should  be  avoided. 


EXPLOSION  OF  GUNPOVvDER. 


419 


1176.  The  time  necessary  for  igniting  powder  varies  accord- 
ing to  circumstances.  For  instance,  damp  powder  requires  a 
longer  time  than  powder  perfectly  dry,  owing  to  the  loss  of 
heat  consequent  on  the  evaporation  of  the  water;  a powder 
the  grain  of  which  has  an  angular  shape  and  rough  surface 
will  be  more  easily  ignited  than  one  of  rounded  shape  and 
smooth  surface;  a light  powder  more  easily  than  a dense  one. 

1177.  IjsrFLA3J3X.\.Tiox. — When  grains  of  powder  are  united 
to  form  a charge,  and  tire  is  communicated  to  one  of  them,  the 
heated  and  expansive  gases  evolved  insinuate  themselves  into 
the  interstices  of  the  charge,  envelop  the  grains,  and  ignite 
them  one  after  another. 

This  propagation  of  ignition  is  called  inflammation,  and  its 
velocity,  the  velocity  of  inflammation.  It  is  much  greater  than 
that  of  combustion,  and  it  should  not  be  confounded  with  it. 
When  powder  is  burned  in  an  open  train,  fine  powder  inflames 
more  rapidly/  than  coarse ; such,  however,  is  not  the  case  in 
ii re-arms,  owing  to  the  diminution  of  the  interstices.  If  a 
charge  were  composed  of  mealed-powder,  the  flame  could  no 
longer  find  its  way  through  the  interstices,  and  the  velocity  of 
inflammation  and  combustion  would  become  the  same. 

1178.  How  supposing  one  grain  or  particle  alone  be  ignited, 
it  will  first  be  inflamed  over  its  whole  surface,  and  the  pro- 
gressive combustion  will  take  place  from  the  exterior  to  the  in- 
terior. Itsrafc  of  comhustionw^W^  therefore  depend  upon  both  its 
shape  and  size,  leaving  out  entirely,  for  the  present,  the  question 
of  density  and  hardness.  A particle  of  spherical  or  cubical 
form  ■will  expose  less  surface  to  ignition  in  proportion  to  its 
volume  than  one  of  an  elongated  or  flat  shape,  and  will  con- 
sequently require  a longer  period  for  the  combustion  of  its  en- 
tire mass ; the  larger  the  particle,  also,  the  longer  will  be  the 
time  required  for  its  combustion. 

1179.  Looking,  then,  at  one  grain  of  powder  by  itself,  we 
may  say  that  the  larger  it  is,  and  the  more  nearly  its  form  ap- 
proaches a sphere,  the  longer  will  its  combustion  take  and  the 
slower  will  be  the  evolution  of  the  gas.  When,  however,  we 
come  to  regard  the  action  of  an  aggregation  of  such  particles, 
as  in  the  charge  of  a gun,  the  rate  of  ignition  of  the  whole 
charge  is  also  aii’eeted  by  the  size  and  shape  of  the  grain. 

1180.  The  part  of  the  charge  first  ignited  is  that  near  the 
vent,  and  the  remainder  is  inflamed  by  contact  with  the  heated 
gas  generated  by  the  combustion  of  this  portion,  so  that  the 
rate  of  igmition  of  the  whole  mass  will  be  regulated  by  the 
gi'eater  or  less  facility  with  which  the  gas  can  penetrate 
thi’oughout  the  charge,  which  is  itself  dependent  upon  the 


420 


NAVAL  ORDNANCE  AND  GUNNERY. 


shape  and  size  of  the  interstices  between  the  erains.  If  tlie 
grains  be  spherical  and  regular  in  form,  the  interstices  will  1)C 
comparatively  laige  and  uniform,  and  the  gas  will  penetrate 
the  mass  with  facility  ; again,  the  larger  tlie  grains,  the  larger 
the  interstices  between  them.  If,  on  the  other  hand,  they  be 
hat  or  flaky  and  irregular  in  shape,  the  passage  of  the  gas  will 
be  more  chflicult,  and  the  rate  of  inflammation  of  the  charge 
reduced. 

1181.  We  see,  therefore,  that  the  considerations  which 
affect  the  more  or  less  rapid  combustion  of  an  individual  grain 
of  gunpowder,  also  affect  the  rate  of  ignition  of  a charge  of  such 
grains,  but  in  an  opposite  direction ; so  that  a form  of  grain 
which  will  individually  burn  rapidly  may  ofier  an  increased 
resistance  to  tlie  passage  of  the  heated  gas  tln-ough  the  charge, 
and  thereby  retard  its  ignition,  while  a grain  which  will  burn 
more  slowly  may  allow  of  the  charge  being  more  rapidly  ignited. 

1182.  i>y  varying  the  size  and  shape  of  the  grain  alone,  a 
powdei'  may  therefore  be  obtained,  a charge  of  which  shall  be 
ignited  rapidly  throughout,  but  burn  comparatively  slowly,  or 
one  wliich  shall  be  ignited  more  slowly,  but  when  once  inflamed 
burn  very  rapidly.  It  is  necessary  to  draw  a clear  distinction  be- 
tween a rapidly-igniting  and  a cpiickly -burning  powder. 

1183.  Ratio  of  the  Charge. — The  heat  developed  increases 
with  the  charge,  and  as  the  velocity  of  the  gases  increases  with 
their  temperature,  it  is  tlierefore  evident  that  a large  charge  is 
consumed  cpricker  than  a small  one ; it  is  also  true  that  the  loss 
of  heat  absorbed  by  the  sm-face  of  the  bore  is  much  less  sensible 
when  the  charge  is  great  than  when  it  is  small,  that  is,  the 
cpnantity  absorbed  is  proportional  to  the  surface,  or  the  scpiare 
of  the  calibre  of  the  gun  and  the  heat  developed  increases  as 
the  cube  of  the  calibre. 

1184.  The  Resistance  to  he  overcome. — When  the  projectile 
offers  a great  resistance  it  is  not  so  quickly  displaced  as  when 
the  resistance  is  slight;  its  motion  in  the  first  instance  is  then  less 
rapid,  and  it  evidently  follows  that  the  inflammation  takes  place 
in  a space  more  confined  as  the  resistance  to  be  overcome  is 
greater.  The  smaller  this  space  is,  the  more  heat  is  concentrated, 
the  higher  the  temperature  of  the  gases  is  raised,  and  consequent- 
ly their  velocity  is  increased,  the  inflamed  gases  have  a less  dis- 
tance to  e.xpand.  through,  and  there  follows  from  all  these  causes 
a train  of  effects  which  accelerates  the  inflammation  of  the 
charge. 

1185.  The  Place  where  the  Fire  is  Communicated  to  the 
Charge. — When  a cpiantity  of  powder  is  contained  in  an  cii- 
closerl  space,  all  the  sides  of  which  offer  an  equal  resistance, 


EXPLOSION  OF  GUNPOWDER. 


421 


it  is  evident  that  the  complete  inflammation  will  be  the  qnieh- 
est  possible  when  the  fire  is  applied  to  the  centre  of  the 
charge. 

In  cannon,  however,  the  force  developed  does  not  meet 
with  the  same  resistance  in  all  directions  ; the  projectile  yields 
as  soon  as  sufficient  force  acts  tipon  it,  and  as  the  combustion  of 
tlie  powder  requires  a definite  interval  of  time,  it  follows  that  a 
great  part  of  the  charge  is  not  consiuned  until  after  the  dis- 
placement of  the  projectile. 

In'ow  the  position  of  the  interior  orifice  of  the  vent  may 
influence  the  time  required  to  displace  the  projectile,  and  this 
influences  the  inflammation  of  the  charge.  For  example,  with 
the  regulation  vent,  it  is  the  upper  part  of  the  charge  which 
first  takes  fire ; the  inflammation  is  communicated  to  the  adja- 
cent parts  and  promptly  reaches  the  projectile ; the  gases  ex- 
panding displace  it,  and  the  inflammation  takes  place  in  a larger 
space  than  that  at  first  occupied  by  the  charge. 

1186.  The  Glazing  of  the  grains  facilitates  the  rapid  trans- 
mission of  the  flame  through  the  mass. 

1187.  — CowBUSTiox. — The  velocity  of  combustion  is  the 
space  passed  over  by  the  surface  of  combustion  in  a second  of 
time,  measured  in  a direction  perpendicular  to  this  surface. 
The  diameter  of  the  grains  in  “ cannon  powder  ” does  not  ex- 
need  0.15  inch ; the  time  required  for  combustion  of  such 
grains,  therefore,  is  altogether  too  transient  to  be  ascertained 
by  direct  observation. 

1188.  The  velocity  of  combustion  may  be  determined  l)y 
compressing  the  powder  composition  into  a tube  and  burning 
it,  or  by  burning  \h.Q press-calie.  In  the  latter  case  take  a prism 
of  the  cake  of  convenient  length  and  about  one  inch  square  at 
the  base,  smear  the  sides  with  hog's-lard  and  place  it  on  end  in 
a shallow  dish  of  water.  The  object  of  the  lard  is  to  prevent 
the  spread  of  the  flame  to  the  sides,  and  the  water  is  to  prevent 
the  lower  end  from  being  ignited  by  burning  drops  of  powdei\ 
Set  the  upper  end  on  fire  and  note  the  time  of  burning  of  the 
column  with  a stop-watch  beating  tenths  of  seconds. 

In  either  way  it  will  be  shown  that  the  composition,  if 
homogeneous,  burns  in  parallel  layers,  and  that  the  velocity  of 
combustion  is  uninfluenced  by  the  size  of  the  columns  or  by 
the  temperature  and  pressure  of  the  surrounding  gas. 

1189.  Now  take  a spherical  grain  of  powder  of  homogene- 
ous structure,  and  so  hard  jrressed  that  the  gas  cannot  penetrate 
it.  Apply  fire  to  any  part  of  its  surface ; the  flame  will  imme- 
diately envelop  it,  and  burn  away  the  first  spherical  layer; 
the  radii  of  the  grain  undergoing  equal  reductions  in  equal 


422 


NAVAL  ORDNANCE  AND  GDNNERT. 


successive  portions  of  time.  T"lien  at  the  end  of  half  the  time 
required  for  the  total  combustion  of  the  whole  grain,  there  will 
remain  uneonsnmed  a sphere  of  which  the  radius  is  one  half 
the  original  radius,  but  the  volume  will  be  only  one-eighth 
the  original  volume  (spheres  being  to  each  other  as  the  cubes 
of  their  radii.)  At  this  epoch,  therefore,  seven-eighths  of  the 
grain  will  have  been  consumed. 

1190.  It  will  be  seen  from  this,  that  for  equal  intervals  of 
time,  those  taken  in  the  first  period  of  combustion  givm  forth 
very  much  larger  amounts  of  gas  than  those  taken  in  the  last ; 
and  that  with  a charge  of  such  grains  the  gas  is  evolved  in  the 
inverse  order  desired : the  evolution  being  greatest  while  the 
velocity  of  the  projectile  is  least,  and  least  Avhile  that  velocity 
is  the  greatest ; thus  giving  rise  to  excessive  pressure  at  and 
near  the  seat  of  the  charge.  This  may  be  remedied  in  some 
degree  l)y  inci'easing  the  size  of  the  grain,  the  effect  of  wh.ich 
will  be  to  diminish  the  amount  of  gas  evolved  in  the  first 
inffant  of  time,  and  thereby  diminish  the  pressure  in  the  gun. 

1191.  It  may  be  shown  by  direct  experiment  that  the  burn- 
ing of  a grain  of  powder  in  a fire-arm  is  progressive,  and  that 
the  size  of  the  grain  exerts  a great  influence  on  the  velocity  of 
the  projectile.  For  instance,  if  piece  of  iXiQ press-calce  was 
placed  in  a small  mortar  and  fired,  little  or  no  motion  Avoukl  be 
given  to  the  projectile.  If  this  piece  be  divided  into  seven  or 
eight  parts,  the  projectile  will  be  thrown  a short  distance,  and 
by  increasing  the  number  of  the  parts  or  grains,  so  will  the 
effect  of  the  powder  on  the  projectile  also  increase. 

1192.  The  progressive  burning  of  powder  is  further  con- 
firmed by  the  fact,  that  burning  grains  are  sometimes  projected 
from  the  gun  with  sufficient  force  to  perforate  screens  of  paper 
and  wood  at  considerable  distance.  It  is  even  found  that  they 
are  set  on  fire  in  the  gun  and  afterward  extinguished  in  the  air 
before  they  are  completely  consumed.  The  large  grains  of  pow- 
der used  in  the  fifteen-incli  gun  are  sometimes  thrown  out  burn- 
ing to  a distance  of  one  hundred  yards. 

1193.  The  Velocity  of  Combustion  varies  with  the  jyio- 
rity,  proportions,  trituration,  density,  and  condition  of  the  in- 
gredients, also  with  the  pressure  under  which  the  powder  is 
burned. 

Purity  of  Ingredients. — To  secure  the  greatest  velocity  of 
combustion,  it  is  necessary  that  the  nitre  and  sulphur  should  be 
pure  or  nearly  so. 

This  can  always  be  effected  by  a proper  attention  to  the  pre- 
scribed modes  of  refining ; but  with  charcoal  it  is  different,  for 
the  part  which  it  plays  in  combuscion  depends  upon  certain 


EXPLOSION  OF  GUNPOIYDER. 


423 


cliaractenstics  wliicli  are  indicated  by  its  color  and  texture.  Tlie 
velocity  of  combustion  will  be  greater  for  red  charcoal  than 
for  that  which  is  black  and  strongly  calcined;  and  for  light  airl 
friable  charcoal,  than  that  which  is  hard  and  compact. 

1194.  Proportiom. — By  varying  th.e  proportions  tlie  velocity 
of  combustion  is  varied. 

The  increase  of  sulphur  tends  to  make  a more  violent  explo- 
sion and  a more  Cjuickly  kindling  mixture,  as  the  sulphur  is  tlie 
kindling  ingredient.  Too  much  charcoal  causes  too  slow  burn- 
ing. The  diminution  of  the  snlphur.or  nitre  checks  the  rapidity 
of  combustion,  but  may  be  made  up  by  using  more  inflamma- 
ble charcoal.  The  quality  of  the  charcoal  is  powerfully  affected 
by  the  temperature  at  vdiich  it  is  made.  That  made  at  a low 
temperature,  or  red  charcoal,  contains  more  hydrogen  and  less 
carbon,  is  more  inflammable,  and  burns  more  rapidly,  but,  fro7ii 
its  smaller  proportion  of  carbon,  must  be  used  in  greater  quan- 
tity. It  may  be  said  that  the  charcoal  is  the  varying  ingredi- 
ent ; so  that  the  proportions  used  at  any  time  will  depend  upon 
the  quality  of  the  charcoal.  In  all  naval  ]iowder,  great  cai'e  is 
taken  to  get  a uniform  quality  of  black  coal,  giving  the  nearest 
attainable  approach  to  pure  carbon. 

1195.  Trituration. — Gunpowder,  unlike  nitro-glycerine,  ful- 
minate of  mercury,  and  other  detonating  substances,  is  not  a. 
chemical  compound  but  only  a mechanical  mixture.  By  the' 
incorporating  process  during  manufacture  the  three  substances- 
of  which  powder  is  composed  are  so  intimately  mingled  that  the 
eye  cannot  detect  the  presence  of  any  particular  one.  They  are,, 
notwithstanding,  only  mixed,  and  the  saltpetre  can  be  readily 
dissolved  out  by  water,  or  the  sulphur  sublimed  in  the  form  of 
a vapor,  by  the  application  of  a moderate  heat,  leaving  in  either 
case  the  other  two  ingredients  chemically  unchanged.  The  more 
intimate  the  mixture,  the  more  nearly  does  gunpowder  approach 
to  a chemical  compound,  and  the  more  violent  is  its  combus- 
tion ; but  there  always  must  remain  a vast  ditference  between 
the  most  complete  mechanical  mixture  and  the  most  unstable- 
chemical  compound.  For  this  reason  the  combustion  of  gun- 
powder is  only  very  rapidly  progressive  and  not  instantaneous,, 
as  is  the  case  with  the  violent  explosives  mentioned  above.  It 
is  this  difference  that  renders  gunpow'der  so  valuable  as  a pro- 
pelling agent,  for  were  it  not  for  its  comparatively  mild  action, 
no  gun  could  be  made  sufficiently  strong  to  resist  its  force.  The 
material  of  the  cannon  would  be  broken  before  the  inertia  of 
the  projectile  could  be  overcome. 

1196.  Demit]). — The  density  and  hardness  of  the  grains  of 
powder  are  of  quite  as  vital  importance  as  their  size  and  form,  in 
determining  the  rate  of  ignition  and  combustion  of  a charge. 


42i 


NAVAL  ORDNANCE  AND  GUNNERY. 


By  density  is  meant  the  quantity  of  powder  actually  present 
in  a given  hulk. 

It  is  important  that  this  quality  should  not  be  confounded 
with  hardness.  A substance  may  he  very  liard  and  yet  he  of  a 
low  density.  A powder  with  a very  hard  surface  may  be  really 
less  dense  than  anotlier,  the  surface  of  wliich  is  softer.  Of 
course  very  high  density  cannot  he  communicated  without  pro- 
ducing a considerable  degree  of  hardne.ss ; hut  powder  can  be 
made  hard  without  rendering  it  very  dense,  by  pressing  the 
dost  in  a comparatively  dry  state. 

1107.  Hardness  seems  to  bear  a direct  relation  to  the  power 
exerted  in  compressing,  while  density  does  not.  Powder-dust,  at  a 
high  degree  of  moisture,  say  G per  cent,  can  he  made  very  dense  by 
application  of  moderate  pressure,  while  that  of  1 per  cent,  can 
only  he  brought  to  the  same  point  in  density  by  the  exertion  of 
enormous  force.  Of  the  two  the  latter  will  be  the  harder  j^owder. 

1198.  Explosive  Fouce. — By  using  a slower  burniug  pow- 
der less  heat  and  pressure  are  evolved  at  first,  and,  the  waste  of 
heat  in  the  stage  of  initial  pressure  being  less,  more  heat  remains 
for  expansive  action.  Hence  the  slower  burning  powder  is  weaker 
at  first  but  stronger  afterwards ; and  although  tlie  total  quantity 
of  gas  be  only  the  same  and  the  pressure  not  so  great  at  any 
point,  yet  the  aggregate  pressure  throughout  the  bore  may 
equal  that  of  the  more  energetic  and  more  dangerous  powders. 

1199.  The  cpiestiou  of  the  instantaneous  e.xplosion  of  gun- 
poAvder  is  one  of  extreme  importance,  for,  independently  of  the 
increase  of  the  actual  amount  of  pressure  Avhich  it  would  cause 
in  a gun,  this  pressure  Avhen  suddenly  applied  Avill  have  tAviee 
the  destructive  effect  that  the  same  pressure  AA’ould  have  if 

• sloAvly  applied. 

1200.  The  objects  to  be  attained  in  regulating  the  size  and 
•density  of  the  grains  are,  the  greatest  possible  Amlocity  of  pro- 
jectile combined  with  the  least  strain  on  the  gun.  These  can- 
not be  obtained  by  one  set  of  conditions  for  all  natures  of  ord- 
liance.  A small  projectile  moves  quickly  and  relieves  the 
strain  in  a still  greater  ratio.  A heavy  projectile  not  only  moves 
sloAAdy,  but  even  a considerable  motion  does  not  relieve  the 

• strain  in  a proportionate  manner,  because  the  column  of  pow- 
der is  larger  in  a large  gun  than  in  a small  gun.  IVitli  small- 
arms,  consequently,  Ave  must  use  fine-grain  poAvdei’,  but  large- 
grain  poAvder  Avith  heavy  guns. 

1201.  Owing  to  the  effect  Avhich  heat  and  pressure  have  in 
accelerating  combustion,  the  size  and  density  of  grain  that  will 
suit  any  particular  gun,  and  as  a consequence  the  actual  pressure 
lin  the  gun  itself,  can  only  be  determined  ])ractically. 

12Q2.  The  explosive  force  of  gunpowder  may  be  calcidated 


EXPLOSION  OF  GUNPOWDER. 


425 


from  the  products  of  combustion,  on  the  assumption  that  certain 
laws  hold  good,  such  as  that  the  tension  of  a gas  varies  with  its 
density  and  also  with  its  temperature.  It  must,  however,  he  re- 
memhered  that  these  laws  have  been  verified  only  within  certain 
limits  of  pressure  and  temperature ; and  therefore,  Avheii  Ave 
come  to  such  Amrv  great  pressures  and  temperatures  as  are  met 
with  in  the  explosion  of  poAvder,  any  conclusions  founded  on 
them  must  he  received  Avith  caution,  until  the  results  have  been 
confirmed  by  experiment. 

1203.  It  is  of  little  practical  utility  to  attempt  to  determine 
the  exact  value  of  the  explosive  force  of  gunpowder,  for  the  na- 
ture of  the  action  in  charges  of  equal  weights  Avill  vary  consid- 
erably not  only  from  atmospheric  causes,  or  in  consec[uence  of 
imperfections  in  the  manufacture  or  in  the  qualities  of  the  in- 
gredients, but  with  the  size,  form,  and  density  of  the  grains  and 
\heform  of  the  cartridge. 

1204.  PEODUCTS  OF  COMBUSTIOH._It  was  form-' 
erly  supposed  that  in  the  combustion  of  gunpowder  the  Avhole 
of  the  oxygen  of  the  nitre  entered  into  combination  with  the 
carbon,  forming  carbonic  acid,  the  nitrogen  being  set  free, 
while  the  potassium  combined  with  the  sulphur,  forming  potas- 
sium sulphide,  thus: 

2KNO3  + S + 30  = Iv„S  + + 3CO„_. 

Although  the  proportions  indicated  by  the  first  term  of  this 
formula  would  coincide  very  closely  Avith  the  proportions  in 
which  the  ingredients  are  ordinarily  mixed,  if  the  charcoal  used 
were  pure  carhon,  that  coincidence  disappears  when  the  actual 
composition  of  the  brown  charcoal  generally  used  is  taken  into 
account.  Thus  the  formula  Avould  give  : 

2KEO3 202.1  = 74.84  per  cent. 

S 32.  = 11.84  “ “ 

30 36.  = 13.32  “ “ 

If,  however,  Ave  substitute  for  0 the  constituents  of  broAvn 
charcoal  as  given  below,  we  have : 

Eitre  ; 74.84  per  cent. 

Sulphur 11.84  “ 

Oarbon 9.69  “ “ 

Ilydi’ogen 39  “ “ 

Oxygen... 2.97  “ “ 

Ash. . . .27  “ “ 

Wherein  the  O 2.97  per  cent,  corresponds  to  6.2  per  cent, 
additional  nitre.  . 

It  has  been  found,  too,  that  the  actual  products  of  the  com- 
bustion are  much  more  complicated  than  this  theory  Avould  in- 
dicate, and  that  they  vary  greatly  Avith  the  conditions  of  the 
pressure  and  temperature  under  which  the  explosion  takes  place. 


42G 


NAVAL  OKDNANCE  AND  GUNNERY. 


1205.  Tlie  elaborate  investigations  of  tlie  precincts  of  com- 
bustion of  gunpowder  made  some  years  since  by  Vogel,  Ijy 
Bunsen  and  Scbiscbkotf,  by  Link,  and  by  Koi'olye,  all  coincided 
in  proving  that  very  little  potassium  sulphide  is  formed,  but 
that  it  becomes  oxydized  to  potassium  snlphate  and  hypo-sul- 
phate, and  that  notable  quantities  of  potassium  carbonate  are 
produced. 

It  results  from  this  that  a much  smaller  volume  of  gas  is  gen- 
erated than  the  old  theory  calls  for  ; only  ^ as  much,  according 
to  Bunsen. 

Bunsen  found  that  one  gramme  of  gunpowder  yielded  193 
cubic  centimetres  of  gas  reduced  to  o°C,  at  the  normal  atmos- 
pheric pressure. 

1206.  The  experiments  referred  to  above  were  made  under 
conditions  differing  widely  from  those  obtained  in  actual  prac- 
tice, and  since  the  above  researches  were  made,  experiments 
have  been  instituted  both  in  America  and  Enssia  so  as  to  imi- 
tate the  condition  of  pressure  and  temperature  which  exist 
where  powder  is  fired  in  guns.  They  agree  in  finding  that 
when  gunpowder  is  exploded  at  a low  temperature,  K„SO^  is 
formed,  but  under  high  pressure  and  great  heat  the  sulphate  is 
partially  reduced  to  sulphide,  thus  accounting  for  the  well- 
known  fact,  that  if  a gun  be  washed  out  after  a discharge  a large 
amount  of  potassium  sulphide  is  found  in  the  solution.  Potas- 
sium carbonate  seems  to  be  formed  under  all  conditions. 

1207.  The  following  is  the  result  of  an  analysis  of  the  residue 
obtained  from  firing  a cannon  loaded  with  shot,  with  a charge 
of  3 pounds  of  powder  : 

IVSO, 15.00 

Iv„C03 37.00 

K:SA 8.29 


K„S  . . 
iCCyS 

c:.... 

Sand. . 


3S.1S 

.33 

.09 

.82 


Composition  of  the  powder  used  : 

KNO3 

S 

Charcoal 

Moisture 


99.71 

7-1.175 

9.890 

1BS35 

1.000 


99.900 


INSPECTION  OF  GUNPOWDER. 


427 


Composition  of  the  Charcoal : 

C 

II 

o 

Ash 


72.5 

2.9 

22.3 

2.3 


100.0 

The  composition  of  the  residue  was  found  to  vary  consider- 
ably in  experiments  made  with  different  kinds  of  fire-arms,  and 
with  different  charges  of  powder  and  shot,  but  the  general  con- 
elusion  was,  that  the  increased  pressure,  by  prolonging  tlie  time 
of  interaction  of  the  ingredients,  and  by  augmenting  the  heat, 
gives  rise  to  more  gas  and  leaves  less  oxygen  fixed  in  the  residue. 

1208.  Berthelot,  in  an  important  research  made  during  the 
late  war  in  France,  “ On  the  Explosive  Force  of  Gunpowder,” 
draws  attention  to  the  importance  of  bearing  in  mind  the  phe- 
nomena of  dissociation,  according  to  which,  the  products  found 
after  cooling  do  not  exist  at  the  high  temperature  pi'oduced  by 
explosion,  but  are  replaced  by  more  simple  compounds. 


Section  III. — Inspection  of  Gimpowder. 

1209.  Inspection. — Before  gunpowder  is  received  from  the 
manufacturer  it  is  inspected  and  proved.  As  it  may  have  the 
required  strength  and  still  be  incapable  of  bemg  long  preserved, 
it  is  necessary  to  inquire  into  the  manner  in  which  the  mixing, 
pounding,  and  other  manipulations  have  been  performed,  for 
upon  these  the  powder  depends  in  a great  measure  for  the 
preservation  of  its  qualities. 

1210.  General  Qualities. — Gunpowder  should  be  of  an 
even-sized  grain,  angular  and  irregular  in  form,  without  shaiqi 
corners,  and  very  hard.  It  should  be  free  from  dust ; and  when 
Hashed  in  small  quantities  in  a copper  plate,  it  should  leave  no 
bead  or  fouling.  It  should  give  the  required  initial  velocity  to 
the  projectile,  and  not  more  than  the  maximum  pressure  on  the 
gun,  and  should  absorb  but  little  moisture  from  the  air. 

1211.  Examination  by  Hand  will  determine  the  firmness, 
crispness,  and  shape  of  the  grains,  and  their  freedom  from  dust ; 
which  cau  also  be  ascertained  by  pouring  a portion  of  powder 
quickly  from  one  vessel  to  another. 

1212.  Flashing. — This  is  done  by  firing  about  ten  grains 
with  a red-hot  iron.  Should  there  be  many  sparks,  or  should 
white  globules  or  beads  appear,  or  any  spots  be  left  on  the 
plate,  it  would  indicate  that  the  incorporation  had  not  been 


428 


NAVAL  ORDNANCE  AND  GUNNERY. 


effectually  performed,  or  that  the  proper  proportion  of  ingredi- 
ents had  not  been  employed. 

1213.  Size  or  Grain. — The  size  of  the  grain  is  tested  hy 
standard  sieves  made  of  sheet-brass  pierced  vrith  round-holes. 
These  sieves  are  five  in  number,  two  being  used  for  each  kind 
of  powder.  ISTos.  1 and  2 for  rifie,  2 and  3 for  cannon,  and  4 
and  5 for  shell  powder. 

The  holes  are  of  the  following  diameters,  viz. : 
jSTo.  1,  .3  of  an  inch  ) 

hs^o.  2,  .1.5  “ f 

Xo.  2,  .15  “ ] ^ 

No.  3,  .10  » f 

No.  4,  .06  » I Q,  „ 

No.  5,  .02  “ [ 

The  size  of  the  grain  is  required  to  confoim  to  the  follow- 
ing : 

Passthrough  No.  1 all  ] -p-fl 

Eemain  on  No.  2 all  f 

Passthrough  No.  2 all)  ^ 

Remain  on  3 j Cannon. 

Passthrough  No.  4 all  | q-, 

Eemain  on  No.  5 alU 


Ten  jier  cent,  of  variation  is  tolerated. 

1214.  Geaviaietric  Density  is  the  weight  of  a given  meas- 
ured quantity ; it  is  usually  ex'pressed  by  the  weight  of"a  cubic  foot 
in  ounces.  The  cube  box  is  constructed  with  great  accuracy, 
and  the  powder  is  simply  poured  into  it  until  filled.  A hat 
ruler  is  then  drawn  across  the  surface,  and  the  box  with  its  con- 
tents weighed.  The  weight  of  the  box  when  empty  being  de- 
ducted, that  of  a cubic  foot  of  the  powder  under  examination  is 
ascertained. 

This  cannot  be  relied  on  for  the  true  density,  as  the  size 
and  shape  of  the  grain  may  make  the  denser  powder  seem 
the  lighter. 

Cannon-powder  should  have  a gravimetric  density  of  about 
875  oz.,  and  not  exceeding  900  oz.,  to  the  cubic  foot.  It  varies 
with  different  makers  from  875  to  975. 

1215.  Specific  Geavita'. — Assuming  the  usual  values  as- 
signed to  the  elements  of  gunpowder  in  the  scale  of  specific 
gravity,  the  absolute  density  of  a homogeneous  mass  of  the 
mixt  ire  is  1.985.  This  point  is  never  reached  in  practical 
manufacture,  and  even  in  GoA'ernment  supplies  the  variation 
from  this  standard  is  such  that  frequently  in  a given  hidk, 
poAvder  consists  of  25  per  cent,  of  pores,  in  addition  to  all  air- 
spaces between  the  grains. 


INSPECTION  OF  GUNPOAVDER. 


429 


The  specific  gravity  of  gunpowder  is  generally  between  1.65 
and  1.75.  It  is  important  that  it  should  be  determined  with  the 
greatest  accuracy. 

1216.  The  MEECunT  DENsniETEK,'"  invented  by  Colonel 
Mallet,  of  the  French  army,  is  the  best  apparatus  yet  devised  for 
this  purpose,  and  has, 


with  slight  inodifi- 
cations,'  been  adop- 
ted for  testing  Navy 
powder.  It  is  an 
instrument  by  means 
of  Avhieh,  in  con- 
nection with  an  air- 
pump  and  a delicate 
b,ilance,  the  density 
of  a solid  may  be 
obtained.  (Fig.  274.) 

It  consist  of  two 
principal  parts — the 
immo\uxble  standard, 

A,  with  various  fit- 
tings, and  a hollow 
ellipsoidal  glass  ves- 
sel, A',  called  the 
vase,  having  tubular 
extremities,  each 
furnished  with  a 
metallic  cap  or  col- 
lar, B,  into  which 
is  screwed  a short 
iron  plug,  C,  per- 
forated in  the  di- 
rection of  its  length, 
and  fitted  with  a 
stop-cock.  The  up- 
per orifice  of  the 
ping,  which  screws 
into  the  lower  end 
of  the  vase,  is  cov- 
ered with  a dia- 
phragm of  chamois 
leather,  the  lower  Fig.  274. 

end  of  the  upper 

plug  being  similarly  fitted  with  one  of  v’cry  fine  metallic  gauze. 


* Naval  Ord.  Papers,  No.  1.  Lieut.  Comtnauder  J.  D.  Marvin,  U.  S.  Navy. 


430 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  leather  diaphragm  strains  the  mercury,  that  of  wire 
prevents  grains  of  powder  from  being  sucked  up  into  the 
barometer-tube.  A nozzle,  d,  screwed  to  the  lower  end  of  the 
bottom  ping,  dij)S  into  the  mercmy  in  the  dish,  e.  The 
standard  is  a bracket  of  wrought-iron  mounted  on  a table  of 
convenient  height. 

It  is  fitted  with  a thermometer,  g,  a gi’adnated  scale  for  the 
barometer-tube,  h,  and  a socket  with  a stop-cock,  i,  into  which 
the  barometer-tnbe  and  upper  connection  of  the  v'ase  are  screwed. 
A long  bulb,  which  forms  a part  of  the  barometer-tnbe,  sur- 
rounds and  encloses  the  upper  end  of  the  stem.  This  acts  as  a 
receiver  for  the  overflow  of  mercmy,  which  is  liable  to  be  thrown 
up  when  leaks  occur  about  the  connections  of  the  vase  or  tube. 
The  bulb,  which  is  in  general  outline  a cylinder,  contracts  at  its 
top,  terminating  in  a conical  point,  over  which  the  open  end  of 
a flexible  India-rubber  hose  is  slipped,  thus  connecting  the  tube, 
and  through  it  the  vase,  with  the  air-])ump. 

1317.  I 'lie  Ajusiments. — As  all  of  the  different  connections 
of  the  v'ase  where  air-tight  joints  are  made,  are -fitted  with 
leather  washers  of  constantly  changing  thickiress,  it  follows  that 
a variable  degree  of  screwing  up  is  rerpfired  in  order  to  make 
the  junctions  absolutely  perfect.  AYitli  the  plugs  which  screw 
into  the  ends  of  the  vase,  it  is  of  great  importance  tliat  the  ex- 
tent to  wliich  they  enter  should  be  uniform  for  any  given  num- 
ber of  trials  with  the  same  powder,  that  is,  they  should  be  run 
into  the  same  distance  when  each  sample  of  powder  is  tried,  that 
they  were  when  the  vase  was  filled  with  mercury  alone ; for  if 
not  in  far  enough  the  capacity  of  the  vase  is  increased.  In  or- 
der to  control  this  source  of  error  as  far  as  possible,  set-marks 
are  put  on  the  collars  and  on  the  plugs.  So  long  as  these  are 
either  brought  together  or  kept  separated  by  a fixed  and  con- 
stant amount  at  different  trials  the  experiment  will  be  accurate. 
As  coincidence  will  probably  only  occur  when  the  washers  are 
new,  the  separation,  as  they  wear  away  or  become  compressed, 
mnst  be  estimated  and  carefully  retained  the  same  at  different 
trials,  so  long  as  the  same  value  is  assumed  for  the  weight  of  the 
vase  filled  with  mercury  alone. 

In  screwing  on  the  nozzle  and  in  screwing  in  the  plugs, 
both  wrenches  should  be  used — one  as  a spanner,  to  hold  against 
the  other  used  as  a wrench,  otherwise  the  cementing  of  the  col- 
lars may  be  started  and  leaks  produced. 

The"  zero  of  the  barometer-scale  is  the  lower  end  of  the  noz- 
zle. The  quantity  of  mercury  in  the  dish  and  the  level  on  which 
the  dish  i-ests  shoiild  be  so  regulated  that  the  immersion  of  the 
nozzle  will  not  be  greater,  when  the  vase  is  full,  thaii  is  neces- 


INSPECTION  OF  GUNPOWDEK. 


431 


sary  to  prevent  tlie  admission  of  air.  If  tins  precantion  be  dis- 
regarded, the  fluctuations  in  the  iieight  of  the  barometic  column 
ai’e  very  liable  to  mislead  by  attacliing  suspicion  to  the  working 
of  the  pumns  or  to  the  cioseness  of  the  densimeter  connections. 

121S.  When  leaks  in  the  connections  of  the  vase  occur  they 
are  indicated  by  air-bubbles,  which  can  be  distinctly  seen  pass- 
ing up  through  the  enclosed  mercury.  They  can  generally  be 
located,  if  about  the  junctions,  by  closing  the  cocks  in  sucecession 
from  down  lap,  meantime  working  the  ]nnnp.  If  about  tlie 
tube-connections,  the  flow  of  air  will  continue  with  all  the  cocks 
closed;  if  below  this,  the  leak  can  be  located  between  the  two 
cocks.  By  tightening  the  junctions  with  the  wrenches,  or,  if  in 
the  cocks,  by  screwing  them  up  with  a screvr-driver,  the  difficulty 
is  readily  overcome.  It  sometimes  happens  that  the  cement 
Avhich  holds  the  collar  to  the  neck  of  the  vase  becomes  cracked 
and  produces  a leak.  This  can  be  located  by  filling  the  vase, 
closing  both  cocks,  and  then  expanding  the  mercury  by  holding 
the  vase  in  the  hands  or  by  wrapping  a warm  cloth  around  it, 
the  effect  of  which  is  to  foi'ce  globules  of  mercury  out  at  the 
point  where  the ' leak  has  occurred.  A mixture  of  tallow  and 
beeswax,  applied  at  the  same  time  that  the  pump  is  worked, 
will  stop  a leak  of  this  kind. 

1219.  When  the  vase  is  unscrewed  after  the  filling,  the 
mercuiy  which  remains  in  the  fine  tubes  of  the  end  plugs  must 
he  carefully  jarred  out.  This  precaution  is  very  important ; for 
as  the  amount  of  mei'cury  which  thus  remains  varies  at  differ- 
ent trials,  the  accuracy  of  the  weight  taken  is  sensibly  affected, 
if  care  is  not  taken  to  remove  all  the  mercury  outside  the  cocks. 
For  this  reason  the  globules  which  adhere  to  the  vase  and  its 
fittings  should  be  removed  by  brushing,  before  an^^  attempt  is 
made  to  get  the  weights.  In  testing  line  powder,  both  plugs 
should  be  unscrewed,  and,  with  the  vase,  carefully  wiped  after 
each  trial ; with  mammoth  this  is  only  occasionally  necessary. 

1220.  Whenever  the  barometer-tube  or  vase  become  coated 
on  the  inside  with  sulphuret  of  mercury,  they  should  be  dis- 
mounted .and  washed  with  aqua  i-egia  (by  measure,  two  parts 
liydrochloric  acid  to  one  part  of  nitric  acid).  In  tlie  event  of 
breaking  the  barometer-tnbe,  expose  the  metallic  socket,  which 
holds  the  lower  end,  to  the  flame  of  a lamp,  until  the  cement 
softens ; remove  the  broken  tube,  and  then  screw  the  socket  in 
]flac3  again.  Coat  the  end  of  the  new  tube  witli  cement,  and 
insert  it  in  the  socket  before  the  latter  cools  off,  taking  care  that 
it  stands  vertical  when  in  place;  for  if  at  all  inclined  it  will  be 
difficult  to  unscrew  it  for  the  purpose  of  cleaning  or  emptying 
the  overflow-bulb. 


432 


NAVAL  ORDNANCE  AND  GUNNERY. 


1221.  The  Aie-pdmp. — The  air-pump  used  with  the  densime- 
ter is  of  the  ordinary  construction,  and  is  mounted  on  a li2;ht 
table.  (Fig.  275.) 

The  vacuum-gauge,  a,  is  in.  an  air-tight  glass  case,  which  is 


Pig.  275. 


placed  between  the  standards  on  -which  the  brake  works.  It  can 
be  shut  off  from  connection  with  the  cylinder  by  the  cock 
and  air  is  admitted  to  it ; and  thence  to  the  cylinder,  etc.,  by 
unscrewing  the  glass  covei-,  which  can  be  turned  by  means  of  a 
chamfered  ring  on  the  brass  collar  into  which  it  iits.  Connec- 
tion with  the  densimeter  is  controlled  by  the  cock  c.  The 
cylinder,  cZ,  of  brass,  oscillates  on  trunnions  at  its  base;  its  con- 
nections with  the  vacuum-gauge  and  .the  hose  leading  to  the 
densimetei’  are  through  the  curved  pipe,  e,  which  is  held  agaiint 
its  several  bearings  by  set-screws.  The  upper  cylinder  head  is 
fitted  with  an  oil-hole  closed  by  the  screw-ping,/",  and  has  an 
overdow-can  g,  to  catch  oil  forced  out  in  exhausting. 

1222.  The  Precautions  to  be  observed  in  using  the  pump, 


INSPECTION  OF  GUNPOTTOEE. 


433 


are : 1.  AlTzays  keep  the  piston-rod  and  piston  well  oiled.  2. 
Keep  the  cocks  h and  c,  and  the  connections  of  the  tube,  e,  air- 
ti2;ht.  3.  Screw  down  the  Tacuum-gauge  case  securely  before 
commencing  to  exhaust.  To  determine  whether  the  pump  is 
tight  and  working  well,  close  the  cock  c under  the  bell-glass 
table,  A,  and  Avork  the  brake. 

The  vacuum-gauge  Avill  show  whether  air  is  admitted,  and 
the  leak  may  be  located  by  the  hissing  sound  made  by  the  air 
rushing  in. 

The  connections  of  the  India-rubber  hose  require  occasional 
looking  to.  The  air-pump  end  is  tightened  by  scTewing  up; 
the  other  can  always  be  made  perfect  by  cutting  off  a short  sec- 
tion, thus  getting  a ubav  and  unstretched  portion  to  adjust  over 
the  end  of  the  barometer-tube  of  the  densimeter. 

1223.  The  Balance. — The  balance  employed  in  the  pro- 
cess of  determining  density,  is  a simple  beam-scale,  constructed 
with  great  accuracy.  (Art.  388.) 

The  great  convenience  of  a decimal  system  of  weights  has 
led  to  the  adoption  of  the  scale  of  grammes  in  ascertaining  the 
density  of  powder. 

The  set  of  weights  used  is  of  5,000  grammes ; approximately 
11  pounds.  The  heaviest,  1 kilogramme,  2,204  pounds ; the 
lightest,  5 centigrammes,  0.75  giains. 

1224.  The  Feogess  of  taking  the  Density.— The  powder 
to  be  tested,  if  of  mammoth  size,  will  require  breaking  up  to  a 
smaller  granulation  ; for  in  its  natui’al  state  it  will  not  readily 
enter  the  vase,  which  is  of  but  one-half-inch  interior  diameter 
at  the  neck.  This  is  readily  and  safely  done  by  using  a light 
steel  hammer,  the  powder  resting  on  a table  of  wood. 

For  convenience  of  computation,  it  is  advisable  to  use  sam- 
ples of  100  grammes ; or,  if  employing  grain  weights,  of  1543.3 
grains. 

Recourse  may  then  be  had  to  tables  (see  Appendix  II.)  for 
finding  the  density. 

1225.  To  tal'e  the  Density. — Weigh  out  the  sample  with 
great  accuracy,  taking  100  grammes,  if  practicable.  The  vase 
being  mountecl,  with  the  nozzle  screwed  in  place  and  well  im- 
mersed in  the  mercury,  close  the  lower  cock,  opening  both  the 
others,  and  exhaust  the  air  from  the  tube  and  A^ase.  When  the 
gauge  shoAvs  nearly  a perfect  A^acuum,  open  the  lower  cock. 
The  mercury  from  the  dish  aahU  then  enter  and  fill  the  A-ase, 
rising  in  the  tubs  to  nearly  the  barometic  height,  the  vacuum 
meanwhile  being  kept  up  by  continuous  pumping.  As  soon  as 
the  column  becomes  stationary,  close  the  loAver  stop-cock  and 
re-admit  the  air  to  the  top  of  the  tubs  by  unscrewing  the  casing 

28 


434 


NAVAL  ORDNANCE  AND  GUNNERY. 


of  tlie  vaciuim-guage ; close  the  other  coehs  and  unscrew  the 
nozzle ; dismount  the  vase,  jar  out  the  mercury  from  the 
tubular  spaces  outside  the  cocks,  brush  the  outside  clean,  an  I 
then  jtlace  the  vase  on  its  rest  and  weigh  it.  Call  this  weight 
of  vase  and  mercury  YM  = W.  Empty  the  vase  by  opening 
the  cocks,  and  allow  the  mercury  to  return  to  the  dish ; also  let 
the  mercury  run  out  of  the  barometer-tube.  If  the  inside  of 
the  vase  is  coated,  unscrew  both  plugs  and  wipe  it  out  with  a 
cloth  ; or,  if  necessary,  wash  it  with  acqua  regia.  TCith  clean 
mercury,  washing  is  rai’ely  required. 

1226.  In  general  practice,  after  having  emptied  the  vase,  one 
plugis  unscrewed,  and  the  sample  of  powder  previously  weighed 
out  is  poured  in.  The  plug  being  again  securely  in  place,  the  vase 
is  mounted  and  the  mercury  pumped  into  it,  passmg  up  through 
the  powder,  tilling  its  interstices,  driving  out  the  air,  and  rising 
to  the  same  height  in  the  tube  as  before.  When  this  point  is 
reached,  close  the  cocks,  admit  the  air,  unscrew  and  weigh  the 
vase  as  before,  calling  the  weight  of  powder,  vase,  and  mer- 
cury PV  ]\I=  W'.  From  these  two  weights,  together  with  that 
of  the  powder  sample,  the  density  is  calculated  by  the  propor- 
tion : 

Density  of  mercury : density  of  powder  = weight  of  mer- 
cury displaced  by  powder : weight  of  powder : or,  if — 

W n=  weight  of  vase  and  mercury, 

W'  — weight  of  powder,  vase,  and  mercury, 
w — weight  of  powdei’, 

D = density  of  mercury, 
d — density  of  powder, 

then  W'  — = weight  of  mercury,  vase,  and  powder,  less  the 

weight  of  powder,  and  W — — w)  = weight  of  mercury 

displaced  by  the  powder,  and  the  proportion  becomes — 

D : eZ  = W — "W'  vj  \ w, 

^ _ D X vj 
or,  a - 

The  weight  of  W should  be  determined  at  the  beginning 
and  end  of  each  set  of  trials,  and  the  mean  be  used  to  correct 
the  result  of  the  whole  scries. 

1227.  The  occasions  will  be  rare  when  the  accuracy  of  the 
results  given  in  the  table  will  be  sufficiently  atfected  by  tem- 
perature to  require  correction ; but  if  the  thermometer  varies 
materially  from  GG°  Fahrenheit,  and  great  accuracy  is  required, 
the  density  of  the  powder  may  be  calculated  by  the  formula 
already  given,  in  which  D will  be  the  density  of  the  mercury 
at  the'temperature  of  the  time  of  observation,  to  be  taken  from 


ESrSPECTIOIT  OF  GUNPOWDER. 


435 


the  table  ; or,  if  no  table  is  at  hand,  the  effect  of  the  tempera- 
ture can  be  computed  by  the  formula — 

_ Do  X 5550 
^ 5550  + t ’ 

in  which  Do  — density  of  mercury  at  zero  centigrade,  and  t = 
any  temperature  above  zero ; or  the  correction  may  be  attained 
with  suthcient  accuracy  for  ordinary  practice  by  multiplying 
the  decimal  .00245  by  the  temperature  expressed  in  degrees 
(centigrade).  This  product,  subtracted  from  13.596,  gives  the 
density  for  the  temperature  under  consideration.  The  propor- 
tion given  above,  viz.,  D : = W — W'  -\-w.w,  must  be  used 

to  compute  the  density  of  the  sample,  if  its  weight  be  other 
than  100  grammes  or  1543.3  grains  ; and  the  actual  value  of  D 
should  also  enter  into  the  calculation  when  the  temperatime 
varies  materially  from  66°  Fahrenheit.  For  example  : 

Suppose  W = 4120  grammes. 

Suppose  W'  = 3400  grammes. 

Suppose  90  grammes, 

and  the  temperature  = 90°  Fahrenheit,  then  D = 13.52,  ap- 
proximately, and  the  density  of  the  sample  is  1.502. 

1228.  Test  of  the  Quality  of  the  Mercury. — The  mercury 
used  should  be  of  specilic  gravity — 13.55055  at  66°  Fahrenheit. 
Its  purity  can  be  tested  by  comparison  with  distilled  water  by 
the  follovvung  process : 

Clean  the  vase  and  its  connections  thoroughly,  and  weigh 
it.  Call  this  weight  a. 

Mount  the  vase  and  fill  it  with  mercury,  and  again  weigh  it, 
calling  the  result  h.  Empty  clean,  and  connect  it  again,  substi- 
tuting a dish  of  distilled  water  for  that  of  mercury  ordinarily 
used.  Fill  the  vase  by  pumping  slowly  to  avoid  overflowing. 
Detach  and  weigh  it  again,  calling  this  last  weight  c ; then — 


G — a 

the  density  of  the  mercury,  which,  if  up  to  the  standard,  will 
coiTCspond  to  that  given  in  the  table  for  the  temperature  at  the 
time  of  trial. 

Tlie  mercury  used  with  the  densimeter  should  frecpiently  be 
strained  through  chamois-leather  to  remove  impurities  which 
are  accidentally  introduced  into  it  in  experimenting. 


436 


NAYAL  ORDNANCE  AND  GUNNERY. 


Form  for  recording  exjperiments  with  the  densimeter. 


Record  Nomber. 

Date. 

Class  or  Chorac- 
ter  of  Sample. 

<W 

its 

*0  Ol 

o 

> S 

CJ-,  9 . 
<=> 

si 

■s  i 

Density. 

1 Thermometer. 

1 

1229.  Use  of  the  Tables. — Tables  I.  and  II.  are  arranged 
for  nse  precisely  like  a table  of  logaritbms  of  numbers.  (Ap- 
pendix II.) 

Fxample.,  Table  I — Uequired  tbe  density  corresponding  to 
W — lY'  -\-w  = 824.5.  Opposite  824,  in  tbe  left-baud  column, 
will  be  found  in  tbe  column  beaded  o=  for  tbe  first  three  fig- 
ures, 1.G4 ; and  looking  to  tbe  right  in  the  column  beaded  .5,  tbe 
remaining  figures  348  are  taken,  giving  1.G4348  for  tbe  den- 
sity. 

If  "W  — TY' -|- w = 821.6,  tbe  first  figures  are  taken  from 
below,  as  indicated  by  tbe  bar  over  928  in  tbe  column  beaded  G. 

Example,  Table  II.  (Appendix  II.) 

732. G grammes  = 11304.1  grains. 

734.5  grammes  = 11333.3  grains. 

1230.  MUZZLE  VELOCITY. — A projectile  on  leaving  tbe 
bore  of  a gun  will  have  acquired  its  maximum  velocity,  gener- 
ally termed  tbe  initial  velocity.  This  essentially  depends  upon 
tbe  powder,  and  is  an  important  test  of  its  quality. 

1231.  ELECTRO-BALLISTIC  MACIIIXES.— Tbe  accu- 
rate determination  of  tbe  velocity  of  a projectile  at  any  point 
of  its  trajectory,  lias  been  one  of  tbe  most  difficult  problems  in 
tbe  science  of  gunnery.  It  has  exercised  tbe  talents  and  in- 


ELECTRO-BALLISTIC  MACHINES. 


437 


gemiity  of  tlie  bsst  scientific  minds  of  tlie  age,  and  has  given 
rise  to  much  interesting  discussion  and  many  valuable  experi- 
ments. The  ■wondrous  mechanical  skill  of  the  day,  and  our 
mastery  over  the  powers  of  electricity,  have,  however,  recently 
given  ns  instruments  which,  in  their  results,  more  than  realize 
the  brightest  dreams  of  the  experimenters  of  a century  ago. 
Their  bulky,  unwieldy,  and  expensive  machines  have  given 
place  to  the  neat  and  compact  chronoseope,  which,  witli  its 
pencil  of  electrical  light,  now  notes  with  unerring  certainty  in- 
finitesimal intervals  of  time. 

1232.  BALLISTIC  PENDULUM.— The  ballistic  pendu- 
lum invented  by  Kobins,  who  is  justly  held  to  be  tlie  pioneer 
of  modern  gunnery,  was  first  used  in  1740,  with  the  object  of 
measuring  the  velocity  of  projectiles  and  the  resistance  of  the 
air.  It  consisted  of  a tripod,  from  the  top  of  which  was  sus- 
pended a pendulum  vibrating  freely  on  its  axis  of  suspension. 
The  bob  was  arranged,  and  of  a size,  to  receive  the  impact  of 
the  projectile.  Its  prolongation  below  the  bob  was  so  con- 
trived as  to  register  the  degree  of  vibration. 

If  such  a pendulum,  being  at  rest,  is  struck  by  a body  of 
known  weight,  and  the  vibration  which  it  makes  after  the  blow 
is  known,  the  velocity  of  the  striking  body  may  thence  be  de- 
termined. The  quantity  of  motion  of  the  body  before  impact 
is  equal  to  that  of  the  pendulum  and  body  after  impact. 

1233.  GUN  PENDULUM. — The  use  of  the  gnu  pendu- 
lum seems  to  have  been  suggested  by  Robins,  although  Count 
Rumford  first  reported,  in  1781,  the  results  of  various  experi- 
ments made  with  it  for  the  determination  of  the  initial  velocity 
of  projectiles,  and  the  most  advantageous  position  of  the  vent. 
It  consisted  of  a gim  suspended  in  a horizontal  position,  and 
vibrating  freely  ; the  arc  of  its  recoil  being  accurately  measured 
when  the  gun  was  fired. 

The  quantity  of  motion  of  the  gun  as  a pendulum  is  equal 
to  that  of  the  projectile,  charge  of  powder,  and  the  air.  Prom 
this  the  velocity  of  the  projectile  may  be  deduced. 

Extended  experiments  ■with  both  the  ballistic  and  gun 
pendulums  Avere  made  in  England,  from  1775  to  1791,  by 
Hutton  ; at  Metz  in  1839  and  1840  ; and  in  the  United  States 
from  1843  to  1848,  by  Major  Mordecai  of  the  Ordnance  De- 
partment. The  instruments  used  in  this  country  Avere  the 
most  perfect  of  their  kind,  and  the  importance  of  the  results 
obtained  cannot  be  too  highly  estimated.  The  instraments 
Averc,  however,  A^ery  expensive,  had  to  be  erected  on  perma^ 
nent  structures,  and*  were  rather  limited  in  their  application. 

1234.  ELECTRICITY. — Professor  Wheatstone,  in  1840, 


438 


NAVAL  ORDNANCE  AND  GUNNERY. 


first  suggested  the  employment  of  electricity  in  determining 
the  velocity  of  projectiles.  It  Avas  tried  in  the  folloAviug  man- 
ner : Two  screens  or  targets  of  wire  were  so  placed  as  to  be 
cut  by  the  ball  during  its  flight.  Each  screen  formed  part  of 
the  circuit  connecting  a galvanic  battery  and  an  electro-magnet. 
This  last  suspended  a pencil  over  a cylinder  made  to  revolve 
uniformly.  The  rupturing  of  the  target  wire  by  the  ball  in- 
terrupted the  current,  and  caused  the  magnet  to  release  the 
pencil,  which  made  a mark  on  the  revolving  cylinder.  The 
time  of  revolution  being  known,  the  angle  between  these  two 
marks  determined  the  time  of  the  ball’s  passage  between  the 
two  targets ; and  knoAving  the  distance  of  the  targets  apart,  the 
velocity  coidd  be  readily  ascertained. 

1235.  The  application  of  electricity,  as  seen  in  this  first 
attempt,  depends  upon  its  very  great  velocity,  Avhich  may  be 
considered  instantaneous  for  shoit  distances.  The  greatest 
difficulty  to  be  overcome  lies  in  the  manner  of  recording  and 
preserving  the  time  of  flight,  or,  rather,  of  registering  the  in- 
stant the  projectile  strikes  each  target.  When  this  is  per- 
formed Avith  the  necessary  accuracy,  and  the  time  it  takes  a 
projectile  to  pass  over  a certain  distance  thus  obtained,  the 
mean  velocity  Avill  be  the  cpiotient  of  the  space  divided  by  the 
time.  It  may  be  said,  Avithout  appreciable  error,  that  this 
mean  velocity  is  the  actual  velocity  of  the  projectile  at  the 
middle  point  of  the  space  passed  over. 

123G.  In  May,  1843,  Professor  Henry,  now  secretary  of  the 
Smithsonian  Institirtion,  presented  and  read  a paper  before  the 
American  Philosophical  Society,  “ On  a ucav  method  of  de- 
termining the  velocity  of  projectiles.”  It  consisted  in  the  a}> 
plication  of  the  instantaneous  transmission  of  an  electrical 
action.  Two  Avire  screens  placed  in  the  path  of  the  projectile 
were  made  to  form  piarts  of  galvanic  currents,  connected  with 
the  axis  and  surface  of  a revolving  cylinder  Avhich  Avas  covered 
by  a graduated  paper.  The  terminal  point  of  the  AA-fi’e  at  the 
surface  did  not  quite  touch  the  paper,  and  the  interruption  of 
the  primary  current  by  the  rupture  of  the  Avire  of  the  screen 
by  the  projectile,  induced  an  intense  secondary  current,  on  the 
principle  of  the  common  coil  machine,  Avhich  gave  a sp)ark  that 
pierced  the  paper  at  the  instant  of  the  rupture. 

To  Professor  Henry  belongs  the  credit  of  first  proposing 
the  use  of  the  spark  from  Avhat  is  now  knoAvn  as  the  Euhm- 
korff  coil,  Avhich  has  been  since  adopted  in  the  most  improved 
and  successful  instruments. 

Attention  was  thus  early  drawn  to  the  novel  question  of 
devising  and  constructing  a machine  based  on  the  employment 


ELECTRO-BALLISTIC  JIACHINES. 


439 


of  electricity,  and  to  serve  in  solving  the  most  difficnlt  problems 
in  gunnery.  We  will  describe  the  most  successful  of  the  vari- 
ous instruments  in  use. 

1237.  Navez-Leuks  Chbonoscope. — This  is  probably  the 
most  successful  of  all  the  pendulum  instruments,  where  the 
value  of  the  time  is  expressed  in  arc.  It  may  be  said  to  consist 
of  two  separate  instruments : the  pendulum  and  the  dis- 
jvnctor. 

1238.  The  Pendulum. — An  upright  plate  of  vulcanite  with 
a graduated  arc,  A (Fig.  276),  mounted  on  a stand,  snpjjorts 
two  pendulums,  two  electro-magnets,  a pair  of  springs,  and  the 


Circuit  from  the  battery  wMch  magnetizes  the  chronometer 

electro-magnet. 

Circuit  from  the  battery  ■which  magnetizes  the  register 

electro-magnet. 

Arrangement  of  the  second  circuit  to  investigate  the  valve 

of  the  coefficient  x. 

pivot  upon  which  the  escapement  system  works.  One  of  the 
pendulums,  a,  is  termed  the  chronometer  pendulum.,  and  tlie 
other,  h,  the  register  pendulum and  the  magnets  are  so  ad- 
justed, one  behind  each  pendulum,  that  when  magnetized  by  a 
current  of  electricity  they  will  just  sustain  the  bobs  of  their 
respective  pendulums,  into  both  of  which  a piece  of  soft  h’on 
is  inserted. 


440 


NAVAL  ORDNANCE  AND  GUNNERY. 


1239.  An  index-needle,  having  a vernier  at  the  end  to  slide 
along  the  graduated  arc,  is  riveted  to  a steel  disk,  c,  working  in 
the  same  axis  as  the  chronometer  pendulum,  with  which  it 
oscillates,  simply  by  friction,  until  clamped  by  the  action  of  the 
escapement. 

1240.  The  springs  are  attached  to  the  vertical  plate,  and 
pass  one  on  each  side  of  the  steel  disk,  c ; near  the  ends  of  the 
springs  are  two  cleats,  one  on  each  spring,  between  which  a 
wedge-lever,  e,  can  be  adjusted  to  keep  the  springs  apart ; two 
other  cleats  close  on  the  disk  of  the  index-needle,  which  is  be- 
tween the  springs,  when  the  wedge-lever,  e,  is  displaced  by  the 
face  of  the  stirrup,  d. 

1241.  The  rod  of  the  register  pendulum  is  provided  with  aii 
arc  canying  a stirrup,  d,  which,  in  its  descent  when  the  pendu- 
lum is  released,  knocks  away  the  wedge-lever,  e,  from  between 
the  springs,  and  so  closes  them  upon  the  disk,  c,  of  the  index- 
needle,  thus  clamping  it. 

1242.  The  TJisjunctor.  — Thi?,  consists  of  a small  stand,  B, 
on  which  are  two  pieces  of  brass, /y,  each  provided  with  a pres- 
sure-screw, a brass  spring,  g,  fastened  by  another  pressure- 
screw,  and  a cam,  4,  to  work  the  spring  ; the  brass  pieces  have 
platinum  points,  separated  from  each  other  by  a very  short  in- 
terval, and  the  spring  has  also  a platinum  point  below  it,  which, 
when  pressed  down  by  the  action  of  the  cam,  connects  the  two 
other  points ; thus  connecting,  when  requisite,  the  circuits 
through  the  apj^aratus. 

1243.  The  Electric  Currents  are  obtained  by  means  of 
Bunsen’s  voltaic  batteries,  there  being  two  circuits  for  an  ordi- 
nary experiment,  one  (Fig.  276)  passing  through  the  magnet 
of  the  chronometer  pendulum  and  the  first  screw,  the  other 
through  the  magnet  of  the  register  pendulum  and  the  second 
screw  ; as  both  pass  through  the  disjunctor,  the  simultaneous 
disjunction  of  l)oth  circuits  can  be  effected  by  turning  the 
cam,  releasing  the  spring,  and  so  disconnecting  the  platinum 
points. 

1244.  Arrangement  of  Targets.  — TAq  apparatus  is  placed 
in  a small  house  at  a distance  of  about  130  yards  from  the  gun, 
so  that  it  may  not  be  effected  by  the  firing,  and  the  arrange- 
ment of  the  gun  and  targets  is  as  follows : The  first  target 
(Fig.  276)  is  placed  at  a distance  of  10  yards  in  front  of  the 
muzzle  of  the  piece,  and  the  second  target  40  yards  beyond  the 
former ; both  targets  are  of  the  same  construction  and  dimen- 
sions; each  consisting  of  a wooden  frame  having  copper 
wires  stretched  across  in  parallel  rows  by  means  of  pins  in  the 
sides  of  the  frame,  and  these  wii’es  are  broken  by  the  passage 


ELECTRO-BALLISTIC  MACHINES. 


441 


of  tlie  projectile  throiigli  them.  In  order  to  protect  the  wires 
of  the  first  target  from  the  action  of  the  gas,  a ivooden  screen 
is  placed  about  40  inches  from  this  target,  between  it  and  the 
gun  ; the  screen  has  a circular  hole,  about  1^  calibres  in  diam- 
eter, through  which  the  projectile  passes. 

1245.  "Operation  of  the  Instrument. — The  gun  is  fired  the 
projectile  passes  through  the  first  target,  breaks  the  first  cir- 
cuit, and  demagnetizes  the  magnet  of  the  chronometer  pendu- 
lum ; the  boh  begins  to  fall,  carrying  with  it  the  index-needle. 
When  the  projectile  cuts  the  wires  of  the  second  target,  the 
second  circuit  is  broken,  and  the  magnet  of  the  register  pendu- 
lum is  demagnetized ; the  bob  falls,  carrying  with  it  the  arc 
and  stirrup,  which  in  its  descent  knocks  away  the  wedge-lever 
and  clamps  the  index-needle. 

1246.  The  time  due  to  this  arc  of  vibration  can,  by  the 
theory  of  the  pendulum,  be  readily  ascertained,  but  it  must  be 
greater  than  the  time  taken  by  the  projectile  to  pass  from  one 
target  to  the  other  ; for  a certain  small  interval  of  time  elapses 
between  the  rupture  of  the  second  circuit  and  the  clamping  of 
the  index-needle.  This  small  portion  of  time  is  found  by 
means  of  the  disjuuctor,  before  the  gun  is  fired,  by  breaking 
both  circuits  at  once,  and  the  small  arc  so  found  must  be  de- 
ducted from  the  arc  determined  by  firing  the  gun. 

1247.  Benton’s  Thread  YELOcniETEu. — This  is  a gra\dty 
instrument  in  which  the  weights  are  suspended  by  the  tension 
of  a cord,  and  it  may  be  worked  with  common  thread  in  place 
of  the  usual  electro-magnetic  currents. 

The  principle  involved  in  this  arrangement  is,  that  the  loos- 
ening eSect  of  cutting  a taut  tlmead  is  transmitted  to  equal  dis- 
tances along  the  thread  from  the  point  of  rupture,  in  equal,  or 
sensibly  equal,  times.  It  is  a principle  that  can  be  applied  to 
others  of  the  large  class  of  machines  for  measuring  small  inter- 
vals of  time. 

The  peculiar  advantages  found  in  the  use  of  threads  over 
electricity  are,  simplicity  and  cheapness  of  the  apparatus,  free- 
dom from  acid  and  water  for  the  batteries,  and  the  certainty 
and  ease  with  which  it  can  be  operated  by  a single  person,  and 
that  person  the  one  wdio  fires  the  gun. 

The  Velocimeter  may  be  depended  upon  to  give  results  suf- 
ficiently accurate  for  all  the  practical  purposes  of  proving  pow- 
der and  making  ballistic  calculations. 

For  the  purpose  of  explanation,  the  appai’atus  may  be  divided 
into  the  time-marker,  oy  pendulrnn^machine,  the  targets  Ho.  1 
and  Ho.  2,  and  the  threads. 

1248.  Pendulum  FIachine. — The  pendidum  machine  is 


442 


NAVAL  ORDNANCE  AND  GUNNERY. 


shown  in  Fig.  277.  is  a bed-plate  of  metal,  which  supports  a 
graduated  aiv,  l>.  This  arc  is  placed  in  a vertical  position  by 
means  of  thumbscrews  and  spirit-levels  attached  to  it ; and  it 


is  graduated  into  degrees  and  fifths,  commencing  at  the  lowest 
point  of  the  arc,  and  ending  at  90°. 

p p'  are  two  pendulums  having  a common  axis  of  motion 
passing  through  the  centre,  and  perpendicular  to  the  plane  of 
the  arc.  The  bob  of  the  pendulum^.?' is  hxed,  but  that  oi p can 
be  moved  up  and  down  with  a thmnb-screw,  so  as  to  make  the 
times  of  vibration  equal. 

1249.  The  aj)paratus  to  record  the  point  at  which  the  pen- 
dulums pass  each  other  Avhen  they  fall  is  attached  to  the  pro- 
longation of  the  suspeiisi on-rod  p\  and  consists  of  a small  pin 
enclosed  in  a brass  tube  ; the  end  of  the  pin  near  the  arc  has  a 
sharp  point,  and  the  other  is  terminated  with  a head  the  sur- 
face of  which  is  oblique  to  the  plane  of  the  arc. 

As  the  pendulums  pass  each  other,  a blunt  steel  point  attached 
to  the  lower  extremity  of  the  suspension-rod  p strikes  against 
the  oblique  surface  of  the  head  of  the  pin,  which  presses  the 
point  into  a piece  of  paper  clamped  to  the  arc,  leaving  a small 
puncture  to  mark  the  point  of  passage.  An  improvement  to 
the  foregoing  consists  in  attaching  to  the  pendulum  yi'  a delicate 
bent  lever,  which  carries  on  its  point  a small  quantity  of 
print er's-ink ; the  pendulum  y?  presses  upon  this  lever,  causing 
the  point  to  touch  the  arc  and  leave  a small  dot  opposite  to  the 
point  where  the  pendulums  pass  each  other. 

1250.  The  Compressors. — The  leve^'-compressors.,  A A',  are 
made  to  hold  up  the  pendulums  by  tightening  the  threads,  B B', 
leading  to  the  two  targets.  When  the  threads  are  severed  at 
the  targets  by  the  projectile  and  slacken,  the  compressors  are 


ELECTEO-BALLISTIC  MACHINES. 


443 


forced  back  by  their  springs,  and  the  penduiums  are  released 
and  immediately  begin  to  tall. 

The  compressors  are 
shown  in  detail  in  Fig.  278. 

They  have  each  a slight 
notch  at  the  lower  end  to  re- 
ceive the  sharp  end  of  the 
pendulum-rod,  D,  and  hold 
it  firmly  in  a horizontal  posi- 
tion. At  the  upper  end  is 
also  a notch  for  attaching 
the  thread.  G represents 
the  spring  which  presses  the 
compressor  away  from  the 
pendulum  when  the  thi’ead 
is  severed. 

1251.  The  pendulum  ma- 
chine should  be  placed  equi- 
distant from  the  two  targets, 
and  sufficiently  remote  from 
the  piece  not  to  be  affected 
by  the  jar  of  the  discharge 
before  both  pendulums  have  commenced  to  fall.  In  the  case  of 
small-arms,  it  may  be  placed  directly  in  the  plane  of  fire ; but 
in  the  case  of  cannon,  it  should  be  at  least  100  feet  to  the  right 
or  left  of  it.  (See  Fig.  279.)  In  the  figure,  target  Flo.  1 is 


placed  125  feet  from  the  muzzle  of  the  piece.  At  this  distance 
the  thread  will  be  severed  by  the  ball  before  it  can  be  broken 
by  burning  grains  of  powder.  For  ordinary  purposes,  how- 
ever, target  F7o.  1 may  be  placed  directly  in  the  muzzle  of  the 
piece,  by  attaching  it  to  a vertical  string  stretched  across  the 
muzzle.  A board  supported  on  two  posts  may  be  used  to 


444: 


NAVAL  ORDNANCE  AND  GUNNERY. 


d<, 


Fig.  280. 


screen  the  thread  leading  to  the  pendulum  from  target 

No.  2. 

1252.  Targets  for  Ca/rmon  are  similar  in  construction,  and 
composed  of  a single  post  fixed  in  the  ground,  to  which  are  at- 
tached horizontal  arms,  as  shown  in  Fig.  279.  A thread,  d d 
(Fig.  280),  is  stretched  vertically  between  these  arms,  to  which  is 

attached  the  thread  leading  to  the 
pendulum  at  one  side.  The  point 
of  attachment  of  this  tliread 
should  he  a little  below  where  the 
projectile  cuts  the  vertical  thread, 
and  is  shown  at  i.  Both  threads 
to  the  pendulum  passthrough  the 
loops  of  the  compressors,  and  are 
fastened  to  posts  set  in  the  ground, 
in  such  relative  positions  to  each 
other  and  the  pendulum  that  the 
compressors  will  sustain  the  pendulums  vrhen  the  threads  are 
tightened,  and  will  relax  their  hold  when  broken.  'When  can- 
non are  carefully  aimed,  the  projectile  will  cut  both  vertical 
threads  directly  ; hut  in  the  case  of  small-arms,  it  is  found  diffi- 
cult to  ensure  the  cutting  of  the  thread  of  No.  2 target  without 
a special  arrangement. 

1253.  Targets  for  Small-arms.— No.  1,  for  small- 
arms,  consists  of  a piece  of  board  (Fig.  281)  with  a vertical 

opening  to  serve  as  a 
rest  for  the  muzzl  e of  the 
gun.  Across  this  open- 
ing, and  directly  in 
front  of  the  muzzle,  is 
stretched  a short  hori- 
zontal thread  secured 
to  two  leather  washers. 

The  thread  a to 
pendulum  No.  1 is 
drawn  around  the  mid- 
dle of  the  horizontal 
thread,  and  secured  at 
the  leather  washer,  b. 

The  muzzle  of  the 
piece  is  in  contact  Avith 
the  intersection  of  the 
threads,  which  should  he  a little  below  the  centre  of  the  bore. 
The  thread  J)  is  cut  the  instant  the  bullet  reaches  the  muzzle, 
and  the  thread  a slackens,  generally,  Avithout  breaking. 


ELECTRO-BALLISTIC  MACHINES. 


445 


Target  ISTo.  2,  for  small-arms  (Fig.  282),  is  composed  of  an 


iron  target-plate,  B,  1 inch  thick,  which  swings  freely  on 


The  lower  back 


edge 


hori- 
of 


Fig. 


zontal  trunnions  at  its  upper  edge, 
the  plate  rests  lightly  against 
the  back  of  a sharp  knife- 
blade,  D,  hinged  at  E. 

The  thread,  I,  leading  to 
pendulum  hi o.  2 is  wrapped 
around  the  slitted  part  in 
which  the  knife-blade  oper- 
ates, and  fastened  to  the 
leather  washer,  F.  0 C 
are  two  flat-iron  bars  bolted 
to  a post  of  wood  let  into  the 
ground,  and  serve  as  sup- 
ports of  the  trunnions  of  tlie 
target-plate,  B.  When  the 
bullet  strikes  the  plate,  B,  the  knife-blade,  D,  is  pressed  back- 
wards, cutting  the  thread,  I,  and  releasing  the  pendulum.  C 
and  F[  are  screens  of  boiler-plate  to  protect  the  thread  and 
knife  from  fragments  of  the  bullet. 

The  target-plate,  B,  is  made  of  tough  wrought-iron  about  6 
inches  wide,  6 inches  deep,  and  1 inch  thick. 

The  knife  should  be  made  as  sharp  as  possible,  so  that  a 
slight  tap  of  the  finger  on  the  target-plate  will  suffice  to  cut  the . 
thread. 

1254.  To  Deteemtne  the  Time. — It  is  considered  that  each 
pendulum  begins  to  move  at  the  instant  the  projectile  cuts  the 
thread,  and  that  the  interval  of  time  corresponds  to  the  diflerence 
of  the  ai’cs  described  by  the  pendulums  up  to  the  time  of  meeting. 

Let  m and  m'  (Fig.  283)  represent  the  positions  of  the  two 
pendulums  before  rupture,  and  let  the  interval  between  the  rup- 
ture be  such  that  the  m ^ m' 

centres  of  oscillation 
will  pass  each  other 
at  L As  the  times 
of  vibration  are  equal, 
the  interval  of  time 
will  correspond  to  the 
arc  i i',  the  arc  m'  i 
being  equal  to  m i'. 

A vertical  line 
through  the  centre  of 
motion  bisects  the  are 

i i'.  The  reading,  therefore,  corresponds  to  one-half  of  the 


1 

V / 

V: 

V ^ 

1 

i 

n 

Fig  283. 


446 


NAVAL  ORDNANCE  AND  GUNNERY. 


required  time,  or  time  of  passage  of  the  projectile  between  the 
threads. 

To  determine  a formula  for  the  time  that  it  takes  for  one  of 
the  pendulums  to  pass  over  a given  arc,  let  I be  the  length  of  the 
equivalent  simple  pendulum,  v the  velocity  of  the  centre  of 
oscillation,  or  point  m',  y the  vertical  distance  passed  over  by 
this  point,  x the  variable  angle  which  the  line  of  suspension 
makes  with  the  horizontal,  and  t'  the  time  necessary  for  the 
point  ml  to  pass  over  an  entire  circumference,  the  radius  of 
which  is  Z,  with  a uniform  velocity,  v,  we  have. 

V = V2gy. 

Siabstituting  for  y its  value  in  terms  of  the  constant  angle 
of  half -oscillation  and  the  variable  angle  x,  the  above  expression 
becomes 

V = V'igl  cos.  (90°—  x)  ’ 

from  which  we  see  that  the  velocity  of  the  pendulmn  increases 
from  its  highest  to  its  lowest  point,  and  vice  versa. 

The  time  t'  is  equal  to  the  circumference  of  the  circle,  the 
radius  of  which  is  I divided  by  the  velocity,  v ; again  dividing 
this  by  360,  we  have  the  time  of  passing  over  each  degree,  or 

^ 2 7T  Z 

360  2yZ  cos.  (90°  — x) 

To  determine  Z,  it  is  necessary  to  change  the  cylindrical  anns 
of  suspension  to  knife-edges,  in  order  to  determine  the  time  of 
vibration  through  a very  small  arc.  The  mean  of  500  vibra- 
tions will  be  very  near  the  exact  time  of  a single  vibration. 
Knowing  the  time  of  a single  vibration,  the  length  of  the  equiv- 
alent simple  pendulum  can  be  obtained  by  the  relation  Z=Z'  t"“, 
in  which  t"  is  this  time,  and  V is  the  length  of  the  simple  second’s 
pendul  um  at  the  place  of  observation. 

In  this  way  all  the  constants  of  the  expression  for  t are 
known,  and  by  assigning  difierent  values  to  a?,  a table  can  be 
formed  from  which  the  times  corresponding  to  the  different 
arcs  can  be  obtained  by  simple  inspection. 

1255.  Le  Boulexge’s  CHKONOGKXPn. — In  Captain  Le  Bou- 
lenge’s  instrument,  the  shot  is  made  successively  to  cut  two 
currents,  and  thus  to  demagnetize  two  electro-magnets  which 
liad  previously  supported  two  heavy  bodies ; the  faU  of  these 
bodies,  under  the  action  of  gravity,  is  the  measure  of  tlie  time 
taken  by  the  shot  to  pass  over  a known  distance. 

1256.  In  the  Kavez-Leurs  instrument  tlie  weight  liberated 
by  the  shot  is  a pendulum  oscillating  in  front  of  a graduated 
arc,  the  angle  described  by  the  pendulum  being  the  measm-e  of 


ELECTRO-BALLISTIC  MACHINES. 


447 


Fig.  284. 


443 


NAVAL  ORDNANCE  AND  GUNNERY. 


* The  instrament  is  here  represented  mounted  on  its  transporting  box.  For 
accurate  work  from  fixed  positions  it  should  be  placed  upon  a pedestal  resting 
upon  masonary ; and  should  be  established  with  all  the  care  which  characterizes 
the  setting  up  of  astronomical  instruments.  This  point  has  received  great  at- 
tention at  the  U.  S.  Naval  Experimental  Battery. 


ELECTRO-BALLISTIC  MACHINES. 


449 


The  column  stands  on  a triangular  base,  upon  ivhich  is  fixed 
the  Trigger^  T.  (Fig.  287.) 

1259. — The  electro-magnet^  A,  supports  a long  cylindrical 
rod  (Fig.  284)  suspended  vertically  and  called  the  Chronometer. 
This  rod  is  partially  covered  with  two  zinc  tubes,  D £,  called 
Registers.  The  electro-magnet.,  B,  sustains  a shorter  rod,  F, 
named  the  Registrar.  The  Trigger  (Fig.  287)  consists  of  a 
circular  steel  knife,  G,  fixed  in  a recess  of  the  spring,  H,  by 
means  of  the  screw,  FT,  which  forms  an  axle  upon  which  it  can 
be  turned  so  as  to  bring  a fresh  portion  of  the  edge  opposite 
the  chronometer. 


The 


spnnc 


H,  can 


be 

“cocked,”  or  restrained,  by 
means  of  the  catch  on  one  end 
of  the  lever,  I.  The  other 
end  of  this  lever  carries  a disk, 

0,  fixed  to  a screw,  by  means 
of  which  it  can  be  raised  or 
lowered  as  required. 

1260.  This  disk  is  verti- 
cally below  the  registrar  when 
suspended  to  its  electro-mag- 
net ; consequently,  when  the 
current  through  the  second 
screen  is  broken,  the  registrar 
falls  on  the  disk  and  releases 
the  spring,  IT.  The  tube,  L 
(Fig.  284),  retains  the  registrar 
after  its  fall. 

If  it  be  required  to  alter 
the  time  taken  by  the  regis- 
trar to  release  the  knife,  it  is 
done  by  raising  or  lowering 
the  disk  of  the  trigger  by 
turning  it  in  the  direction 
with  the  sun  to  hxarease  the 
time,  and  against  the  sun  to 
reduce  it.  The  screw  has  a 
pitch  of  one  millimetre,  and 
tlie  circmnference  of  the  disk 
is  divided  by  notches  into  ten 
equal  parts  in  which  the  pawl, 
r,  works ; by  this  arrangement 
the  disk  can  be  moved  any 
required  number  of  tenths  of  a millhnetre  (within  certain  lim- 
its), and  is  retained  in  the  required  position  by  the  pawl. 

29^ 


450 


NAVAL  OEDNANCE  AND  GUNNERY. 


1261.  Tlie  screw,  M,  passes  tlirougli  tlie  lever  and  acts 
against  the  fulcrum  supporting  it ; it  is  intended  for  regulating 
the  hold  of  the  catch  of  the  lever  on  the  spring,  whi.h  should 
always  be  as  light  as  possible.  Tliis  is  regulated  once  for  all, 
hut  should  the  spring  at  any  time  sliow  a tendency  to  escape  of 
itself,  this  defect  can  he  remedied  hy  slightly  withdrawing  the 
screw,  M. 

1262.  — The  Disjunetor  (Fig.  288)  is  composed  of  a main- 
spring, t,  cari-ying  a cross-piece,  covered  with  insulating  ma- 
terial, and  passing  under  the  two  steel  plates,  q q'.  By  pressing 
the  milled-headed  screw,  z,  the  spring  is  compressed  and 
held  hy  the  catch,  x,  allowing  the  plates,  c[  q',  to  come  into  con- 
tact with  the  metal  pins,  r F,  and  thus  complete  the  circuits 
hy  bringing  the  screws  s v and  s'  v'  into  connection  with  one 
another.  W hen  the  catch,  x,  is  pressed,  the  mainspring  being 
released,  its  cross-piece  strikes  the  two  plates  exactly  at  the 
same  instant,  raises  them  from  the  screws,  and  thus  breaks  both 
currents  identically  at  the  same  time. 

Should  it  be  thought  at  any  time  that  the  disjunetor  is 
Avorking  inaccurately,  the  method  of  testing  it,  and  of  correct- 
ing it  Avhen  out  of  order,  is  very  simple,  and  will  be  described 
under  the  heading  of  “ Method  of  correcting  irregularities.” 

1263.  The  arrangement  of  the  screws  and  electric  current 
is  precisely  the  same  as  when  using  the  Isavez-Leurs  instru- 
ment, except  that  the  chronometer  battery  must  be  increased 
in  strength  (because  its  electro-magnet  is  requu’ed  to  support  a 
greater  Aveight  than  in  the  hlavez-Leiu’S  instrument),  and  a dif- 
ferent method  adopted  for  introducing  the  disjunetor  into  the 
circuit.  With  the  Le  Boulenge  chronograph,  the  two  Avires 
from  the  positive  poles  of  the  batteries  are  not  joined  as  Avith 
the  Navez-Leurs,  but  are  taken  to  the  two  connecting  screAvs, 
s s',  of  the  disjunetor;  and  thus  the  two  currents,  though 
passing  through  the  disjunetor,  are  kept  entirely  separate. 

1264.  The  electro-magnet.  A,  is  magnetized  by  the  current 
passing  through  the  first  screen ; consequently  when  the  shot 
cuts  this  screen,  the  chronometer  is  released  and  falls  freely  in 
a vertical  direction.  The  other  electro-magnet  is  in  the  circuit 
through  the  second  screen,  so  that  the  registrar  falls  A\-hen  this 
screen  is  cut,  and,  striking  the  disk  on  the  free  end  of  the  lever 
of  the  trigger^  liberates  the  spring,  which  carries  forward  the  knife 
until  it  sti’ikes  the  chronometer  in  its  fall  and  makes  an  indent 
in  the  upper  zinc  tube. 

1265.  A very  simple  relation  exists  (as  Avill  be  seen  here- 
after) betAA^een  the  height  of  this  indent  and  the  velocit_y  of  the 
projectile.  It  is  evident  that  the  time  which  elapses  after  the 
fall  of  the  chronometer  before  the  registrar  is  released,  is  the 


ELECTEO-BALLISTIC  MACHINES. 


451 


time  taken  by  tbe  projectile  in  passing  over  the  distance  between 
the  screens;  the  less,  therefore,  the  velocity  of  the  projectile, 
the  further  in  advance  will  the  -chronometer  be,  and  the  higher 
will  be  the  indent. 


Fia.  287. — The  Trigger. 


1266.  A Graduated  Rule  is  used  for  measuring  the  height 
of  the  indent  above  the  zero-point.  It  is  of  brass,  and  is  grad- 
uated on  both  edges ; the  upper  edge  is  a scale  of  equidistant 
parts,  divided  into  millimetres,  reading  to  tenths  Avith  a ver- 
nier, and  is  intended  for  use  in  connection  with  the  tables. 
Tlie  loAver  scale  is  for  reading  off  the  velocity  of  the  qirojectile 
without  any  calculation;  it  is  graduated  in  metres  fora  distance 
between  the  screens  of  50  metres.  The  zero-point  on  the  scale 


452 


NAVAL  OEDNANCE  AND  GUNNEET. 


corresponds  with  the  origin^  or  the  point  at  which  the  knife 
marks  the  chronometer,  if  the  trigger  is  set  in  action  when  it  is 
at  rest.  The  rule  is  fitted  at  the  zero-end  with  a jointed  piece 
having  a slightly  conical  projection,  which  enters  into  a recess 
in  the  bob  of  the  chronometer,  when  applied  for  measuring  the 
marks.  Care  must  be  taken  not  to  injure  this  portion  of  the 
scale,  or  the  measurement  may  be  rendk’ed  inaccurate.* 

12G7.  Tiieoky  of  the  Insteumeht. — As  stated  above,  if  the 
trigger  be  set  in  action  when  the  chronometer  is  at  rest,  a mark 
will  be  made  by  the  knife  on  the  zinc,  which  point  we  will 
call  the  origin,  as  it  is  the  zero-point  from  which  the  height 
of  fall  of  the  chronometer  must  be  calculated. 

Let  II  be  the  height  above  the  origin  of  the  mark  obtained 
by  firing  a projectile  through  the  screens.  Since  the  chronom- 
eter follows  the  law  of  the  fall  of  heavy  bodies, 

_ p'  2 H 

~ y 

will  be  the  time  it  was  in  motion  before  receiving  the  impres- 
sion. How  T'  would  be  the  time  required  by  the  projectile  to 
traverse  the  distance  between  the  screens,  supposing  that  the 
chronometer  commences  to  fall  the  instant  the  projectile  passes 
through  the  first  screen,  and  further,  supposing  that  it  is  struck 
by  the  knife  at  the  precise  instant  the  shot  cuts  the  second  screen. 
Blit  tills  is  not  the  case.  In  fact,  after  the  rupture  of  the  first 
screen,  a certain  time,  6,  elapses  before  the  electro-magnet  is 
demagnetized  sufficiently  to  free  the  chronometer ; the  movement 
of  the  chronometer  will  therefore  be  delayed,  and  the  observed 
time  consequently  diminished,  by  the  quantity  0. 

1268.  Again,  some  time  elapses  between  the  cutting  of  the 
second  screen  and  the  moment  when  the  knife  reaches  the 
chronometer,  viz.,  the  time  required  for  the  following  opera- 
tions : 

6'  for  the  demagnetization  of  the  electro-magnet  support- 
ing the  registrar. 

t'  for  the  fall  of  the  registrar  to  the  disk  of  the  trigger. 
t"  for  the  disengagement  of  the  catch. 
t'"  for  the  knife  to  pass  over  the  horizontal  distance 
which  separates  it  from  the  chronometer. 

How  it  is  evident  that  the  chronometer,  before  it  is  stnick 
by  the  knife,  will  have  been  in  motion  dmlng  the  sum  of  the 
above  time  in  addition  to  the  time  taken  by  the  shot  in  passing 

* The  rule,  being  a proportional  scale,  can  be  used  for  any  distance  between 
Bcrcens.  At  the  U.  S.  Naval  Experimental  Battery  the  interval  is  a hundred 
feet,  and  the  reverse  face  of  the  rule  is  graduated  to  inches  and  decimals,  and 
tables  corresponding  are  used. 


ELECTRO-EALLTSTIC  MACHINES, 


453 


over  tlie  distance  between  tlie  screens.  Consequently  tlie  ob- 
served time,  T',  is  too  great  by  the  sum  of  {O'  -\-t'  t"  -j-  t'"'). 
We  have  also  shown  above  that  T'  is  too  small  by  the  quantity 
d,  the  time  required  to  demagnetize  the  chronometer  electro- 
magnet. Therefore,  to  ascertain  tlie  true  time,  T,  Ave  must 
deduct  from  T'  the  quantity  {O'  -\-t'  1"  + t'"  — 0),  Avhich  we 


We  have  then  T = T'  — 

12G9.  Now  suppose  T = O,  or,  in  other  words,  suppose  the 
shot  to  cut  both  screens  simultaneously,  then  Ave  should  have 


454: 


NAVAL  ORDNANCE  AND  GUNNERY. 


T'  = t.  From  wliieh  it  appears  that  t sFould  be  the  time  re- 
corded on  the  chronometer  if  both  currents  were  cut  identically 
at  the  same  instant.  Tliis  we  can  do  by  using  the  disjunctor,  and 
we  thus  obtain  a mark,  on  the  lower  ziuc  tube,  at  a height  above 
the  origin  ecpual  to  the  space  passed  over  in  the  time  which  we 
call  xlxQdisjunctor-reading  • the  time  corresponding  to  this  read- 
ing must  bo  deducted  from  the  whole  time  recorded  on  the  chro- 
nometer, to  arrive  at  the  time  taken  by  the  shot  to  traverse  the 
distance  between  the  screens.  As  before  stated,  the  disk  of  the 
trigger  can  be  raised  or  lowered  so  that  the  disjunctor-readiiig 
can  be  altered  (if  required)  within  certain  limits,  and  we  can 
thus  regulate  the  instrument  so  that  the  time  t shall  have  a con- 
stant value.  The  value  of  t for  which  the  velocity  scale  has 
been  calculated  is  0".15,  and  the  height  of  the  corresponding 
mark  above  tlie  origin  is  110.370  mill.  (4.248  inches).  Start- 
ing with  this  assumption,  a scale  has  been  calculated  for  a dis- 
tance between  the  screens  of  50  metres,  by  means  of  which  the 
velocity  of  the  projectile  can  be  at  once  determined  without 
the  aid  of  any  calculation.  Should  it  be  necessary  to  place  the 
screens  nearer  to  one  another,  the  velocity  can  be  found  by 
multiplying  the  number  read  off  on  the  scale  by  the  frac- 


tion — , D being  the  actual  distance  between  the  screens  in 
50 


metres. 

1270.  The  method  of  calculating  this  scale  is  as  follows : 
Suppose  the  shot  to  have  a velocity  of  500  metres  a second, 
50 

it  would  take  — ^ = 0".l  to  traverse  the  distance  between  the 


screens. 

The  instrument  will,  therefore,  mark  0".15  (disjunctor-read- 
ing)  -)-  O'hl,  or  0".25,  and  the  corresponding  height  of  fall  from 

the  origin  will  be  H = ip  T'  pX(0.2o)^^ 

Conversely,  if  the  mark  on  the  chronometer  is  613.17  mill, 
above  the  origin,  we  know  that  the  velocity  of  the  projectile  is 
500  metres  a second.  The  disjunctor-reading  being  at  a 
height  corresponding  to  0".15,  and  the  screen  50  metres  apart. 

This  calculation  has  been  made  for  a series  of  velocities  in- 
creasing from  metre  to  metre  for  all  ordinary  velocities,  and 
the  corresponding  heights  engraved  on  the  scale  supplied  with 
the  instrument. 

This  scale  is  inconvenient,  as  it  is  necessary  to  use  a multi- 
plier in  order  to  ascertain  the  velocity  in  feet  corresponding  to 


ELECTRO-BALLISTIC  MACHINES. 


455 


tlie  number  read  off,  and  this  multipler  varies  with  the  distance 
between  the  screens. 

1271.  Method  of  Adjusting  the  Insteumen’'. — Setting  up 
the  Chronograph. — For  transport  the  different  portions  of  the 
instrument  are  packed  in  a box,  wdiich  can  be  made  to  serve 
the  purpose  of  a stand  by  means  of  an  iron  tripod  supplied  with 
it. 

This  arrangement  is  no  doubt  very  convenient  in  cases 
where  it  is  recpiired  to  move  the  instrument  constantly  and  set 
it  up  in  different  positions.  For  proving  powder,  or  in  similar 
cases,  where  the  instrument  is  stationary  it  is  advisable  to  have 
recourse  to  a more  permanent  arrangement,  as  at  the  Experi- 
mental Battery,  Annapolis. 

1272.  The  triangular  piece  which  supports  the  trigger  and 
the  column  is  fastened  to  a heavy  cast-iron  base  by  the  three 
screws  supplied  with  the  instrument.  This  base  is  13  inches 
square  and  1 inch  thick,  and  is  supported  on  four  milled- 
headed  levelling-screws,  which  ivork  in  brass  Y’s  let  into  the 
oak  block. 

1273.  The  instrument  is  permanently  fixed  to  the  stand, 
and  is  covered,  when  not  in  use,  by  a glass  case  to  protect  it 
from  injury,  a small  beaker  containing  calcined  chloride  of  cal- 
cium heing  used  to  absorb  the  moisture  under  the  case. 

1274.  The  electro-magnets  are  fixed  in  position  by  passing 
the  screwed  stems  through  the  column  and  fastening  them  with 
milled-headed  nuts  (Fig.  286).  Two  zinc  tubes,  or  registers,  are 
placed  on  the  chronometer ; to  put  on  the  small  one  the  bob  at 
the  lower  end  must  first  be  unscrewed.  The  tubes  should  be 
pressed  slightly  out  of  shape  before  being  put  on,  to  cause 
them  to  fit  tightly  on  the  rod,  and  not  to  shift  too  easily.  It  is 
well  to  see,  from  time  to  time  during  the  operation,  that  the 
bottom  of  the  tube  is  resting  against  the  bob. 

1275.  The  connections  with  the  battery  and  the  screens 
having  been  established,  and  the  cuiTents  found  to  pass  cor- 
rectly, and  to  be  of  sufficient  strength,  the  next  step  is  to  ad- 
just and  regulate  the  instrument. 

This  consists  of  three  operations,  viz. : 

1st.  Levelling  the  instrument. 

2d.  Eegulating  the  power  of  the  electro-magnets. 

3d.  Regulating  the  height  of  the  disjunctor-reading.' 

1276.  1st.  Levelling  the  Instrument. — For  this  purpose  the 
chronometer  is  used.  After  having  cocked  the  trigger,  sus- 
pend the  chronometer  to  its  elect)'o-magnet,  and  bring  it  into 
its  proper  position  by  means  of  the  levelling-screws. 

In  levelling  from  front  to  rear  see  that  the  inclined  plane 


456 


NAVAL  ORDNANCE  AND  GUNNERY. 


on  the  bob,  on  the  side  opposite  the  number,  rests  very  lightly 
against  the  projecting  edge  of  the  triangular  base. 

To  level  laterally,  the  right  face  of  the  hob  is  brought 
exactly  in  line  with  the  salient  angle  formed  by  tlie  projection 
above  referred  to.  In  this  position  the  left  face  of  the  bob  is 
a short  distance  from  the  screw,  E ; the  edge  of  the  knife  is 
opposite  and  slightly  behind  the  zinc  tube ; and  when  the 
chronometer  falls,  the  projecting  ring  passes  clear  of  the  knife- 
edge.  To  test  whether  this  is  the  case,  break  the  circuit,  by 
means  of  the  disjunctor,  and  notice  whether  there  is  any  fric- 
tion, or  if  anything  catches  during  the  fall. 

To  ascertain  whether  the  chronometer  is  properly  levelled 
from  front  to  rear,  see  that  the  inclined  plane  on  the  bob  rests 
along  its  whole  length  against  the  projecting  edge ; then  remove 
it  sideways  out  of  the  vertical,  by  pushing  the  bob  against  the 
screw,  E,  when  it  will  return  into  its  original  position,  if  prop- 
erly levelled. 

The  levelling  being  completed,  and  the  registrar  suspended 
to  its  electro-magnet,  the  inclined  plane  on  the  bob,  on  the  side 
opposite  the  number,  should  rest  very  lightly  against  the  edge 
of  the  arm,  K.  This  arm  is  fitted  in  a bracket,  and  its  position 
can  be  altered  by  means  of  an  adjusting-screw.  This  adjust- 
ment need  only  be  performed  once  for  all  ordinary  positions 
of  the  instrument  when  used  in  taking  velocities. 

If  the  electro-magnet  and  the  bracket  be  removed  to  the 
upper  part  of  the  column,  as  shown  in  Fig.  285,  it  may  be  nec- 
essary to  readjust  the  arm  in  order  that  the  registrar  may  still 
hang  vertically.  The  levelling  of  the  registrar  is  verified  in  the 
same  manner  as  in  the  case  of  the  chronometer,  viz.,  by  ascer- 
taining— 1st.  That  when  moved  laterally  it  returns  to  its  origi- 
nal position;  2d.  That  it  falls  freely  without  touching  the 
tube,  L. 

1277.  2d.  Regulating  the  Electro-magnets. — This  is  done 
(as  with  the  Navez-Leurs  instrument)  by  withdrawing  the  core 
of  the  magnets  until  they  are  only  capable  of  just  supporting 
the  rods.  It  is  always  an  advantage  to  work  with  weak  mag- 
nets, as  the  variation  in  the  time  required  to  demagnetize  them 
need  not  be  taken  into  account ; should,  however,  their  power 
be  insufficient,  the  operator  will  experience  some  difficulty  in 
suspending  the  I’ods. 

The  following  method  has  been  adopted  for  making  the 
electro-magnets  of  just  sufficient  power  : 

The  chronometer,  with  its  zinc  tubes,  is  increased  in  weight 
by  means  of  a brass  tube,  which  is  slipped  over  the  upper  zinc. 
It  is  then  suspended  to  the  magnet,  and  the  core  gradually 


ELECTEO-BALLISTIC  MACHINES. 


457 


witlidrawn  until  the  power  is  insufficient  to  support  the  weight, 
wlien  it  falls.  The  core  must  be  turned  slowly  and  gently,  so 
as  not  to  free  the  rod  by  any  jar  or  vibration.  The  extra 
weight  is  then  removed,  and  the  chronometer  can  be  suspended 
without  difficulty. 

The  other  magnet  is  regulated  in  the  same  manner,  a 
smaller  brass  tube  being  supplied  for  increasing  the  weight  of 
the  registrar. 

In  order  to  suspend  the  chronometer  to  its  electro-magnet 
without  difficulty,  the  folloiving  method  should  be  adopted  : 
Hold  it  lightly  in  the  left  hand  at  the  centre,  the  fingers  open 
and  towards  the  body ; allow  the  bob  to  rest  upon  the  second 
joint  of  the  first  finger  of  the  right  hand,  the  hand  being  half 
open,  the  palm  vertical  and  turned  towards  the  body,  and  the 
fingers  together ; the  chronometer  is  thus  held  in  a vertical 
position,  the  numbered  face  of  the  bob  being  turned  towards 
the  operator.  Bring  it  in  this  position  to  the  electro-magnet, 
by  placing  the  exterior  surfaces  of  the  two  cones  in  contact, 
and,  as  soon  as  attraction  is  perceived,  let  go  with  the  left  hand, 
still  keeping  the  fingers  near  to  catch  the  chronometer  should  it 
fall.  Then  slowly  lower  the  right  hand,  so  that  the  two  cones, 
sliding  over  one  another,  remain  with  their  points  only  in  con- 
tact, and  place  the  bob  in  its  proper  position  by  moving  the 
first  finger  of  the  right  hand,  upon  which  it  still  rests.  This 
done,  withdraw  the  support  of  the  right  hand  by  lowering  it 
vertically,  when  the  chronometer  will  remain  suspended  in  its 
proper  position.  If  there  should  be  any  vibration  it  will  soon 
cease  from  the  friction  against  the  rest. 

The  registrar  is  suspended  in  the  same  manner,  but  the 
chronometer  is  always  placed  in  position  first. 

Difficulty  is  sometimes  experienced  by  beginners  in  sus- 
pending the  parts  of  the  chronograph ; minute  details  have 
thei'efore  been  given  as  to  the  best  way  of  doing  so. 

The  other  operations  are  exceedingly  simple. 

To  cock  the  disjunctor,  so  as  to  establish  the  currents,  press 
the  milled-headed  screw,  z (Fig.  288),  with  the  centre  finger  of 
the  right  hand,  until  the  spring  is  held  by  the  catch,  x. 

To  break  the  currents  pi’ess  the  catch,  x,  with  the  forefinger 
of  the  right  hand,  the  thumb  being  placed  against  the  sup- 
port,  y. 

In  cocking  the  trigger  care  must  be  taken  not  to  disturb  the 
level  of  the  instrument ; consequently  the  left  hand  only  is 
used,  the  fingers  being  placed  against  the  support  of  the  tube, 
L,  and  the  spring  drawn  back  with  the  thumb  imtil  it  is  held 
by  the  claw  of  the  lever. 


458 


NAVAL  OEDNANCB  AND  GTJNNEET. 


The  trigger  must  always  he  coclzed  before  attempting  to  sus- 
pend the  chronometer. 

1278.  3d.  Regulating  the  Disjunctor  Reading. — As  we 
have  said  before,  this  reading  shonld  represent  a time  = 0”  .15, 
and  the  mark  shoidd  consequently  be  110.37  mill.  al)ove  the 
origin.  This  height  is  shown  on  the  scale  by  a special  inark 
called  disjunction.  To  facilitate  the  operation,  commence  by 
ti’acing  on  the  small  zinc  tube  a circle  at  the  required  height. 
For  this  purpose  fasten  the  vernier  by  means  of  the  clamping- 
screw,  with  the  index  opposite  the  line  marked  “ disjonction.” 
Place  the  chronometer  flat  on  a table  with  the  numbered  face 
next  the  body,  and  apply  the  rale  to  it  by  inserting  the  conical 
point  of  the  hinge  in  the  recess  of  the  bob,  allowing  the  index 
of  the  vernier  to  rest  on  the  zinc.  Support  the  end  of  the  rule 
in  the  i-ight  hand,  and  Avith  the  left  turn  the  tube,  taking  care 
to  keep  it  pressed  against  the  bob  at  the  lower  end  of  the  chro- 
nometer. In  this  manner  a fine  line  is  traced  on  the  tube,  with 
which,  when  the  instrument  is  well  regulated,  the  disjunctor- 
marks  ought  to  correspond. 

The  indent  made  by  the  knife  is  a notch,  clearly  cut  in 
the  metal,  the  base  of  which  is  in  a plane  pei’pendicular  to  the 
axis  of  the  tube.  It  is  the  section  of  this  plane  with  the  tube 
which  must  be  taken  as  the  mark,  and  the  index  of  the  vernier 
must  always  be  brought  against  it  when  reading  the  height  of 
the  indent. 

The  point  of  the  vernier  index  is  of  the  same  form  as  the 
edge  of  the  knife,  and  consequently  fits  accurately  against  the 
plane  (or  lower)  side  of  the  indent,  so  that  there  can  be  no  un- 
certainty in  the  measurement. 

The  instrument  having  been  prepared,  a disjunctor-reading 
is  taken ; if  the  mark  is  exactly  on  the  circle  previously  traced, 
no  alteration  is  necessary,  and  the  experiments  can  be  proceeded 
with  at  once. 

Should  the  mark,  however,  be  above  the  circle,  the  space 
through  Avhich  the  registrar  falls  must  be  diminished  by  raising 
the  disk  of  the  trigger ; if  below,  the  disk  must  be  lowered. 
In  the  former  case  it  is  turned  in  the  contrary  direction  to  the 
sun,  and  in  the  latter  case  Avith  the  sun. 

The  arrangement  by  which  the  amount  of  alteration  in  the 
height  of  the  disk  is  regulated  has  already  been  pointed  out 
when  describing  the  trigger.  'When  the  height  of  the  disk 
has  been  regulated  for  some  previous  experiments,  the  reading 
Avill  not  vary  on  another  occasion  more  than  a few  tenths  of  a 
millimetre,  and  this  can  be  (at  once)  corrected  by  turning  the 


ELECTEO-BALLISTIC  MACHIlSrES. 


459 


disk,  in  tlie  proper  direction,  tlirongli  the  required  miinber  of 
divisions  of  the  circle. 

1279.  Method  of  Takestg  Velocities. — The  instrument  is 
prepared  for  measuring  velocities  in  the  same  maimer  as  for 
taking  the  disjunctor-reading.  First  cock  the  disjunctor,  then 
the  trigger,  and  aftervrards  suspend  the  chronometer  and  reg- 
istrar. Before  suspending  the  rods,  however,  it  is  advisable,  in 
order  to  prevent  the  possibility  of  errors  in  measuring  the 
indents  given  by  ditierent  rounds,  to  make  ink-marks  round 
the  lower  edge  of  the  upper  zinc  tube,  about  one-twentieth  of 
an  inch  apart,  and  to  turn  the  tube  after  each  round  so  as  to 
bring  these  marks  successively  opposite  the  line  on  the  centre 
ring.  Equidistant  lines  are  thus  obtained,  upon  which  the 
marks  of  successive  rounds  will  be  registered. 

The  same  may  be  done  with  the  lower  (or  disjunctor)  tube  ; 
by  this  means  each  tube  can  be  made  to  register  about  twenty 
indents  at  each  end,  and  can  be  turned  end  for  end  when  the 
circle  at  one  extremity  is  completed. 

An  indent  having  been  obtained  on  the  upper  tube  by  firing 
a projectile  through  the  screens,  the  velocity  may  be  ascertained 
in  two  ways : 1st,  by  measuring  the  height  of  the  mark  above 
the  origin,  and  calculating  the  time  and  corresponding  velocity 
from  the  tables ; 2d,  by  measuring  the  velocity  on  the  scale 
adapted  for  that  purpose. 

The  former  method  is  the  more  accurate,  while  the  latter 
takes  less  time,  and,  for  ordinary  purposes,  such  as  the  proof 
of  powder,  indicates  the  velocity  within  sufficiently  narrow 
limits. 

1280.  Method  of  Coekectixg  Irkegulaeities. — When  the 
foregoing  directions  for  adjusting  and  regulating  the  instru- 
ment are  adhered  to,  not  only  do  successive  disjunctor-readings 
taken  between  the  rounds  agree  within  very  narrow  limits,  but 
the  readings  generally  remain  constant  from  one  round  to 
another.  It  is  therefore  sufficient,  when  accustomed  to  the 
chronograph,  in  order  to  ensure  its  regularity,  to  take  a reading 
of  the  disjunctor  after  every  three  or  four  rounds. 

The  operator  must  judge  from  the  regularity  of  these  read- 
ings whether  he  should  repeat  them,  and  whether  it  may  be 
necessary  to  readjust  the  instrument. 

The  following  directions  will  assist  him.  If  the  reading  is 
too  high  or  too  low,  repeat  it ; and  if  the  difference  remains 
constant,  and  is  small,  the  height  of  the  disk  of  the  trigger  need 
only  be  altered.  Should,  however,  the  error  be  considerable, 
indicating  that  there  is  a variation  in  the  force  of  one  of  the 
magnets,  this  force  must  be  regulated. 


4G0 


NAVAL  ORDNANCE  AND  GUNNERY. 


1281.  Should  the  disjunctor-readings  become  irregular,  the 
following  points  must  be  looked  to,  viz. : 

1st.  If  one  of  the  magnets  has  not  become  too  strong. 

2d.  If  the  instrument  is  properly  levelled ; that  is,  if  the 
rods  hang  vertically,  and  do  not  rest  too  heavily  against  the 
support. 

3d.  If  there  be  not  an  imperfect  connection  in  the  circuits, 
including  the  battery  and  the  screens. 

Should  the  mark  obtained  be  indistinct,  the  chronometer 
must  be  brought  nearer  to  the  knife  (by  means  of  the  levelling- 
screws),  care  being  taken  that  it  still  falls  freely  and  without 
friction. 

1282.  If,  during  the  experiments,  one  of  the  currents  be- 
comes broken  without  any  apparent  cause,  try  (after  ascertain- 
ing that  the  screens  are  properly  mended),  whether  there  is 
contact  between  the  plates,  q q',  of  the  disjunctor  (Fig.  288), 
and  the  pins,  r r',  by  removing  the  wire  from  the  binding-screw 
at  one  extremity  of  the  plate,  and  bringing  it  into  contact  with 
the  screw  at  the  other  end.  If  the  current  is  thus  re-estab- 
lished, it  shows  that  the  break  occurs  at  the  point  of  contact  of 
this  plate  with  the  screw,  which  should  be  cleaned  by  passing 
a piece  of  paper  between  them. 

1283.  The  only  parts  of  the  instrument  that  require  special 
attention  are  the  points  of  contact  between  the  rods  and  the 
electro-magnets. 

These  four  points  ought  to  be  kept  clean  and  polished,  and 
it  is  as  well  never  to  touch  them  with  the  fingers,  and  to  rub 
them  frequently  with  a chamois-leather.  . The  rest  of  the 
instrument  may  be  covered  with  rust  and  dirt  without  affecting 
its  working,  whilst  a single  spot  of  rust  on  one  of  these  points 
may  cause  irregularity  in  the  disjunctor-readings.  If  by  acci- 
dent they  should  get  rusty,  very  tine  emery  cloth  must  be  used 
to  clean  them,  care  being  taken  to  rub  round  the  point  so  as 
not  to  alter  its  form. 

1281.  From  the  nature  of  the  instrument  itself  nothing  can 
affect  the  chronometer  while  falling,  and  the  rate  of  falling 
being  according  to  a well-known  and  invariable  law,  it  is  evi- 
dent that  there  can  be  no  constant  error  in  the  measurement  of 
velocities,  provided  that  the  scale  is  correctly  graduated,  and 
the  disjunctor  in  proper  working  order. 

1285.  The  accidental  errors  which  may  he  committed  cor- 
respond to  those  which  odcur  when  a series  of  disjunctor-read- 
ings are  taken,  after  the  instrument  has  been  properly  regu- 
lated ; and  any  one  at  all  accustomed  to  using  the  instrument 
will  see  at  once  that  the  errors  in  determining  velocities  (inclu- 


ELECTRO-BALLISTIC  MACHINES. 


461 


ding  errors  in  reading  the  scale)  do  not  exceed  a few  decime- 
tres, and  that  the  I’csnlts  are  snthciently  accurate  for  ordinary 
experiments,  the  variations  being  far  less  than  those  due  to 
other  causes. 

1280.  If  the  two  currents  are  not  broken  by  the  disjunctor 
identically  at  the  same  instant,  there  will  be  a constant  error 
in  the  readings.  The  disjunctor  is  not  liable  to  get  out  of 
order,  but,  if  required,  its  accuracy  can  at  any  time  be  verified 
as  follows : 

Determine  the  height  of  the  disjunctor-reading,  and  then 
invert  the  currents  by  removing  the  wires  which  were  first  at 
s and  V to  s'  and  v',  and  those  at  s'  and  v'  to  s and  v (Fig.  288), 
so  as  to  send  the  chronometer  current  through  the  side  on  which 
the  registrar  current  first  passed,  and  vice  versa.  Having  done 
this,  take  several  readings,  and  ascertain  whether  they  agree 
with  those  previously  taken,  which  will  be  the  case  if  the  dis- 
junctor is  correct. 

If  there  should  be  any  difference  between  the  height  of 
these  two  series,  it  represents  double  the  error  of  the  disjunctor, 
and  from  the  relative  position  of  the  marks  it  can  be  seen  on 
which  side  contact  is  first  broken ; i.  e.,  which  plate  is  raised 
before  the  other.  To  correct  this  error,  it  is  only  necessary  to 
elevate  or  lower  one  of  the  screws,  v v',  until  both  plates  are 
raised  by  the  cross-piece  of  the  spring  exactly  at  the  same 
moment. 

1287.  SCHULTZ  CHROHOSCOPE.-This  instrument, 
invented  by  Captain  Schultz,  of  the  French  artillery,  is  de- 
signed for  measuring  very  short  intervals  of  time.  By  means 
of  it,  periods  varying  from  thu’ty  seconds  to  the  part  of  a 
second  have  been  measured  with  very  great  approximation, 
and  with  great  ease  and  accuracy.  It  was  introduced  into  the 
United  States  by  Colonel  Laidley  for  the  purpose  of  deter- 
mining the  initial  velocity  of  projectiles  in  the  proof  of  gun- 
powder. 

A tuning-fork,  making  an  ascertained  number  of  vibrations 
per  second,  is  arranged  to  trace  on  the  blackened  surface  of  a 
revolving  cylinder  a sinuous  line,  showing  the  beginning  and 
end  of  each  vibration.  This  sinuous  trace  will  be  an  actual 
scale  of  time.  If,  then,  the  instant  the  projectile  reaches  each 
of  the  two  given  points  in  its  trajectory  be  marked  upon  the 
cylinder,  beside  the  sinuous  line  or  scale  of  time,  the  number 
of  vibrations  comprehended  between  the  two  marks  will  be  an 
exact  measurement  of  the  time  required. 

The  important  parts  of  the  machine  (Fig.  289)  are  thj 
Cylinder^  Vihratiny-forh,  Electric  Interrujyter,  Ruhmlzorff 


462 


NAVAL  OEDNANCE  AND  GUNNEEY. 


^7o^7,  Pendulum^  and  Micrometer  / and,  while  experimenting, 
the  Gcdvanic  Batteries  and  Targets. 

1288.  The  Cylinder,  with  its  connections,  forms  the  most 


1.  Cylinder.  2.  Clock-work.  3.  Pendulum.  4.  Tibra ting-fork. 
5.  Eubmkora  CoiL  C.  Interrupter.  7.  Micrometer.  8.  Target. 

bulky  of  the  working  parts.  A double  motion  of  rotation  and 
translation  is  given  it  by  means  of  a cord  and  weight  acting  on 
a system  of  clockwork.  These  motions  can  also  be  given  sep- 


ELECTKO-BALLISTIO  MACHINES. 


463 


arately  by  band,  independent  of  the  weights.  The  cylinder  is 
detached  from  or  connected  with  the  clockwork  by  a thumb- 
screw that  clamps  one  of  the  wheels ; and  the  sliding  motion  is 
produced  or  stopped  by  closing  or  opening  the  nut  in  which 
the  translating-screw  works. 

The  silver  face  of  the  cylinder  is  covered  with  a thin  coat- 
ing of  lamp-black,  which  is  removed  by  the  ti’ace  and  spark,  and 
the  bright  surface  exposed  in  strong  contrast  to  the  blackened 
parts. 

1289.  The  Yibrating  Forh  stands  immediately  in  front  of 
the  cylinder.  It  is  clamped  tightly  to  the  bed-plate  of  the  ma- 
chine, Avhieh  is  of  iron,  resting  on  a stout  oak  tiible.  On  each 
side  of  the  fork,  supported  on  a stand,  are  two  small  electro- 
magnets, meant  to  originate,  sustain,  and  equalize  its  vibrations, 
and  can  be  set  at  any  required  distance  from  it.  The  left  hrauch 
of  the  fork  is  armed  Avith  a flexible  quill  point,  Avhich  can  be 
made  to  touch  the  e}dinder  at  pleasure,  and  thus  trace  upon  it 
both  the  middle  line  and  the  line  of  vibration,  in  the  form  of 
a helix ; the  former  AA^hile  the  fork  is  at  rest,  and  the  latter 
while  it  is  vibrating. 

1290.  The  Interrupter  is  the  point  of  termination  of  the 
poles  of  the  battery  Avhich  supplies  the  current  for  the  small 
electro-magnets.  It  consists  of  a light  beam  one  end  of  which 
is  fixed,  and  the  other  end,  extending  beneath  two  electro-mag- 
nets and  over  a small  cup  containing  mercury  and  alcohol,  has 
a platinum  blade  attached  wliich  rises  from  or  descends  to  the 
surface  of  the  mercury  as  the  beam  is  affected  by  the  electro- 
magnets above  it.  One  pole  of  the  battery  passes  through  a 
platinum  wire  into  the  mercury  ; the  platinum  blude  at  the  end 
of  the  beam  becomes  the  other  pole,  and  each  time  it  touches 
the  surface  of  the  mercury,  completes  the  circuit  and  excites  the 
electro-magnets  on  each  side  of  the  fork,  as  well  as  those  Avhich 
act  on  the  beam  itself.  The  magnets  lift  the  blade  out  of  the 
mercury  by  attractuig  the  beam  and  thus  rupture  the  cui’rent. 
This  done  the  magnets  lose  their  magnetic  force,  release  the 
beam,  and  the  blade  descends  to  the  mercury,  completing  the 
circuit,  and  so  on.  All  the  electro-magnets  being  in  the  same 
current,  are  subject  to  a change  of  condition  Avith  each  motion 
of  the  beam,  Avh'ich  must  rise  and  fall  as  often  as  the  fork  vi- 
brates, accommodating  itself  to  and  acting  in  unison  with  it,  in 
order  that  the  small  electro-magnets  shall  always  assist  and  neAmr 
retard  the  vibration  of  the  fork. 

Small  sliding  Aveights  are  attached  to  the  beam,  which,  Avhen 
moved,  change  its  time  of  rise  and  fall ; the  mercury-cup,  Avhen 
raised  or  loAvered,  has  the  same  effect.  Should  the  above  means 


464 


NAVAL  ORDNANCE  AND  GUNNERY. 


fail,  recourse  is  had  to  the  nuts  that  clamp  the  beam,  and  these 
are  tightened  or  loosened  until  the  proper  movement  is  obtaiued. 
If  the  fork  vibrates  for  twenty  or  thu'ty  seconds  without  appar- 
ent change,  the  beam  is  supposed  to  be  moving  in  unison  with 
it,  as  there  can  be  no  permanent  vibration  of  the  fork  unless 
this  condition  be  fulfilled. 

1291.  The  RuhmJcorff  Coil. — The  secondary  currents  ob- 
tained by  magnetic  induction  possess  a high  degree  of  intensity, 
and  if  the  circuit  be  broken  at  the  moment  the  current  is  pass- 
ing, a brilliant  spark  will  be  obseiwed  at  the  point  at  which  the 
interruption  is  occasioned. 

The  secondary  currents  are  rendered  efficient  by  means  of 
the  Ruhmkorfl;  coil.  It  consists  of  two  concentric  helices  of 
copper  wire ; the  primary  or  inner  coil  consisting  of  a stouter 
and  shorter  wire  than  the  secondary  or  outer  coil,  which  is  made 
of  a very  thin  Avire,  insulated  by  silk,  and  each  layer  of  coils  is 
carefully  insulated  from  the  adjacent  layer;  a bundle  of  soft 
iron  Avire  is  placed  in  the  axis  of  the  coils.  The  primary  coil  is 
not  continuous  through  its  length,  but  admits  of  being  broken. 
So  long  as  the  current  circulates  uninterruptedly  through  it,  the 
iron  core  becomes  an  artificial  magnet.  As  soon  as  the  current 
is  broken,  however,  the  iron  core  ceases  to  he  a magnet,  but  a 
powerful  secondary  current  is  induced  in  the  secondary  coil, 
which  Avill  emit  a spark  at  any  point  in  its  circuit  Avhere  broken. 

The  power  of  the  instrument,  and  the  intensity  and  striking 
distance  of  the  spark,  may  be  much  increased  by  connecting 
the  primary  Avire  Avith  the  modification  of  the  Leyden  jar,  com- 
monly called  a condenser.  This  consists  of  a pile  of  alternate 
sheets  of  broAvn  paper  or  oU-silk  and  tin-foil. 

To  use  the  Ruhinkorfi  coil,  the  primary  wire  is  connected 
wdth  a battery  and  the  targets ; the  secondary  Avire  Avith  the 
instrument;  one  of  the  ends  is  brought  tlu’ongh  a glass  tube 
close  to  the  cylinder  just  over  the  fork,  the  other  end  is  con- 
nected with  the  bed-plate  and  thence  Avith  the  cylinder  and 
other  parts  of  the  machine,  except  the  support  for  the  glass  tube, 
Avhich  is  carefully  insulated.  By  this  arrangement,  when  the 
primary  current  is  broken  by  rupturing  the  target  Avire,  a sec- 
ondary current  is  induced  and  a spark  is  projected  from  the  end 
in  the  glass  tube  to  the  face  of  the  cylinder,  Avhich  represents 
the  other  end,  where  a bright  spot  beside  the  trace  indicates  the 
exact  instant  the  rupture  took  place. 

1292.  The  Pendulum  is  used  to  determine  the  exact  num- 
ber of  vibrations  of  the  fork  in  a second  of  time,  a matter 
of  the  greatest  importance.  It  is  connected  A\dth  an  ordinary 
clock-work,  and  should  be  regulated  to  beat  half  seconds 


ELECTEO-BALLISTIC  IIACHINES. 


465 


■with  accuracy.  Below  it  is  an  insulated  upright  spring,  the 
movable  end  of  which  is  in  contact  with  a metallic  stand.  To 
determine  the  number  of  tbe  fork’s  vibrations,  the  Ruhmkortf 
coil  is  put  in  connection,  no  longer  with  the  targets,  but  with 
the  pendulum,  one  pole  of  the  primary  current  being  attached  to 
the  spring,  and  the  other  pole  to  the  metallic  stand.  A spring 
is  fixed  to  the  end  of  the  pendulum  itself,  which,  at  every 
double  beat,  strikes  the  insulated  spring  from  its  place,  thus 
breaking  the  current  and  giving  a spark  on  the  cylinder  to  mark 
each  second  of  time.  As  the  cylinder  can  run  for  thirty  sec- 
onds, the  nmnber  of  vibrations  sought  can  be  obtained  wu'th 
close  approximation,  by  dividing  the  entire  number  of  vibra- 
tions registered  on  the  cylinder  by  the  number  of  seconds. 

1293.  The  Micrometer  serves  to  divide  a vibration  on  the 
cylinder  into  very  small  parts  for  close  reading.  It  magnifies 
the  trace,  and,  by  means  of  movable  cross  hairs,  fixes  the  posi- 
tion of  the  spark.  A double  vibration  of  ordinary  length  may 
be  divided  into  2,000  parts,  and  as  each  of  the  former  is  about 
the  portion  of  a second,  the  readings  of  the  micrometer 
may  approximate  to  the  -s-Tnmnr  portion  of  a second  of  time. 

1294.  The  Batteries.- — A Bunsen’s  batteiy  of  eight  cups, 
the  zinc  cylinders  of  wdiich  are  seven  inches  long  and  three 
inches  in  diameter,  is  connected  with  the  interrupter  and  tuning- 
fork  ; and  another  battery  of  two,  three,  or  four  cups  is  con- 
nected with  the  liuhmkortf  coil.  The  number  of  cups  used  with 
the  latter  will  depend  on  the  size  and  distinctness  of  the  spark 
required,  and  on  the  length  of  the  wire  iised.  The  wire  need 
not  be  more  than  .06  inch  in  thickness. 

By  using  a solution  of  bi-chromate  of  potash  instead  of  ni- 
tric acid  in  the  porous  cups,  a saving  in  the  cost  of  the  liquid 
is  effected  and  the  injurious  fumes  of  nitrous  acid  avoided,  with- 
out loss  of  strength  in  the  battery.  The  liquids  in  the  cups 
should  be  renewed,  and  the  parts  of  the  battery  cleaned,  ©ace  a 
week. 

1295.  The  Targets. — In  working  the  instrument  it  is  essen- 
tial that  the  current  pass  only  through  one  target  at  a time, 
there  being  but  one  coil  and  one  battery,  no  matter  how  many 
targets  may  be  used.  After  the  first  target  is  ruptured,,the  cur- 
rent must  be  transferred  to  tbe  succeeding  one  before  the'  pro*- 
jectile  reaches  it,  and  so  on  throughout  the  series.  The- targets 
must  therefore  be  so  made  and  arranged  as  that  each  shall  trans- 
fer the  current  to  the  succeeding  target  the  instant  its  wires  are 
ruptured ; and  that  the  transfer  shall  be  completed  before  the 
projectile  reaches  the  latter. 

To  effect  this,  a wdre  from  one  pole  of  the  battery  connects- 
30 


466 


NAVAL  OEDNANCE  AND  GUNNERY. 


both  targets  on  one  side.  From  the  other  pole  a ■wire  leads  to 
the  first  target,  and  is  attached  to  one  of  two  brass  rods  that  are 
on  the  top  of  the  frame.  A wire  from  the  second  brass  rod 
leads  to  the  second  target.  If  the  rods  he  connected  by  resting 
a piece  of  metal  on  both,  the  current  will  pass  continuously 
through  both  targets ; but  if  the  rods  be  disconnected,  the  cur- 
rent, being  interrupted  by  their  separation,  will  pass  through 
the  first  target  only.  A series  of  brass  levers  are  placed  on  the 
top  of  the  frame,  extending  directly  over  the  two  rods.  From 
their  lower  ends  a wire  passes  down  and  up  to  foimi  the  target ; 
when  the  wire  is  tightened,  the  levers  are  raised  from  contact 
with  the  two  rods.  JSTow,  the  first  target  being  broken,  the  lev- 
ers are  released  by  the  slackening  of  the  wire  and  are  instantly 
pressed  down  upon  the  two  rods  by  a series  of  steel  springs,  and 
the  connection  made  with  the  second  target. 

In  the  experiments  made  at  the  Frankford  Arsenal,  with 
targets  one  foot  apart,  the  current  was  transferred  from  one  to 
the  other  by  means  of  a simple  brass  spring,  in  less  than  xowo 
of  a second  of  time. 

1296.  Principles  of  the  Machine. — 
From  the  above  description  of  its  parts,  it 
will  be  understood  that  the  Forh.,  when 
vibrating,  traces  a scale  of  time  on  the 
coated  surface  of  the  revolving  cylinder, 
the  unit  of  which  is  the  duration  of  a 
double  vibration.  The  value  of  the  unit 
for  this  machine  is  ^ second 

of  time.  The  Interrupter  originates,  sus- 
tains, and  equalizes  the  lateral  c.xtent 
of  the  vibrations  of  the  fork ; and  the 
Coil,  in  connection  with  the  targets,  de- 
posits a spark  beside  the  traced  scale  of 
time,  to  indicate  the  instant  the  wire  of  a 
tarijet  is  broken,  thus  markino;  the  begin- 
ning  and  end  of  each  interval  to  be  meas- 
urecl.  The  Pendulum  serves  to  detennine 
the  number  of  vibrations  made  by  the  fork 
in  a second  of  time. 

The  measurement  of  time  by  this  instru- 
ment, then,  depends  on  the  equality  of 
dmation  of  the  vibrations  made  by  the  fork.  These  vibrations 
are  known  to  be  isochronal  for  the  same  fork,  when  their  am- 
plitude is  constant,  and  are  in  no  way  affected  by  the  motions 
of  the  other  parts  of  the  machine. 

The  vibrations  made  by  the  fork  are  recorded  on  the  cylin- 


c 


d 

Fig.  290. 


ELECTKO-BALLISTIC  MACHINES. 


467 


JfG- 


der  in  the  form  of  a sinuous  line,  as  in  Fig.  290,  making  th6 
scale  of  time.  The  middle  line,  c d,  traced  hj  the  fork  when 
at  rest,  is  of  great  importance,  as  it  divides  the  sinuous  line  and 
gives  the  exact  points  of  the  origin  and 
end  of  each  vibration.  Even  when  not  in 
the  middle,  no  error  can  occur  when 
double  vibrations  are  counted. 

As  expressed  on  the  cylinder,  each  of 
the  double  vibrations  is  sutiiciently  large  to 
admit  of  being  divided  into  tenths  by  the 
eye ; when  greater  accuracy  is  required,  the 
micrometer  must  be  used. 

To  determine  the  value  of  the  interval 
between  two  sparks,  the  number  of  double 
vibrations  are  counted.  Where  both  sparks 
fall  immediately  opposite  the  intersections 
of  the  two  lines,  the  value  will  be  summed 
up  in  entire  double  vibrations,  as  in  Fig. 

290,  X and  y being  the  sparks. 

When  one  or  both  of  the  sparks  do 
not  fall  opposite  an  intersection,  the 
value  of  the  interval,  is  thus  arrived  at. 

In  Fig.  291  the  sparks  are  at  x and  y. 

From  a to  T)  are  twenty-three  double 
vibrations.  By  the  eye  or  the  microme- 
ter, the  distances  a x and  h y are  found 
to  be  .8  and  .25  of  a double  vibration. 

Therefore  x y — 23  -|-  .8  -|-  .25  ==  24.05 
24.05 

double  vibrations  = 7:,..  = .096565 


Fig.  291. 


249.055 


seconds  of  time. 

As  the  velocity 


space 


time  ’ 


suppose  the  space  between  the 


targets  to  be  one  hundred  feet,  then  the  velocity  of  projectile 

will  be  equal  to  = 1035.5  feet  per  second. 

.096565  ^ 

1297.  To  Use  the  Chronoseope. — The  cylinder  is  coated  by 
revolving  it  over  the  flame  of  an  oil-lamp  with  a flat  wick.  This 
takes  ten  minutes,  and  twelve  or  fifteen  rounds  may  be  fired 
before  the  coating  needs  renewal.'  The  operator,  standing  in 
front  of  the  instrument,  releases  the  translating-screw,  pushes 
the  cylinder  to  the  right,  clamps  it  to  the  wheel-work,  and 
throws  the  translating-screw  into  gear  again.  He  then  sets  the 
point  of  the  quill,  at  the  extremity  of  the  fork,  very  lightly 


468  NAVAL  OEDNANCE  AND  GUNNEET. 

against  the  face  of  the  cylinder,  and  releases  the  brake.  While 
rotating,  the  cylinder  will  be  removed  toward  the  left  by  the 


Fig.  292. 

translating-screw,  and  receive  the  trace  of  the  middle  line  in 
the  form  of  a helix.  This  done,  the  quill  is  raised  and  the  cylin- 
der is  pushed  to  the  right  as  before.  The  quill  is  again  set  with 


ELECTEO-BALLISTIC  MACHINES. 


469 


ils  point  exactly  on  the  middle  line,  the  translating-serew  thrown 
into  gear,  the  circuit  of  the  battery  and  the  interrupter  closed, 
and  the  beam  touched  gently  to  start  it  vibrating.  At  this 
point  the  caution  “ Ready ! ” is  given,  the  circuit  of  the  battery 
and  the  RuhmkorfE  coil  promptly  closed,  and  the  cylinder 
started  rotating  when  the  command  “ Fire ! ” is  given.  As  soon 
as  the  report  is  heard,  the  machine  is  stopped  by  the  brake,  both 
currents  opened  and  interrupted,  the  quill  point  removed,  and 
the  cylinder  detached  from  the  wheel-work  ; when  the  operator 
counts  the  result,  while  the  gun  is  being  reloaded,  and  the  tar- 
gets mended  preparatory  to  another  round. 

1298.  The  Bashfokth  Chkonogkaph. — Profr.  Rashforth,  of 
the  Artillery  School,  Woolwich,  England,  has  made  extensive  ex- 
periments to  determine  the  resistance  of  the  air  to  the  motion 
of  rifle  projectiles,  with  a chronograph  of  his  own  invention. 
Fig.  292  gives  a general  view  of  the  instrument. 

1299.  Description. — The  fly-wheel.  A,  is  capable  of  revolv- 
ing about  a vertical  axis,  and  carrying  with  it  the  cylinder,  K, 
which  is  covered  with  prepared  paper  for  the  reception  of  the 
clock  and  screen  records.  The  length  of  the  cylinder  is  12  or 
14  inches,  and  the  diameter  4 inches.  B is  a toothed  wheel  which 
gears  with  the  wheel-work,  M,  so  as  to  allow  the  spring,  CD,  to  be 
slowly  unwrapped  from  its  drum.  The  other  end  of  CD,  being 
attached  to  the  platform,  S,  allows  it  to  descend  slowly  along 
the  slide,  L,  about  J inch  for  each  revolution  of  the  cylinder. 
E E'  are  electro-magnets  ; d d'  are  frames  supporting  the  keep- 
ers ; and^ ' are  the  ends  of  the  springs,  which  act  against  the- 
attraction  of  the  electro-magnets. 

When  the  current  is  interrupted  in  one  circuit,  as  E,  the 
magnetism  of  the  electro-magnet  is  destroyed,  the  spring, y,  car- 
ries back  the  keeper,  which,  by  means  of  the  arm,  a,  gives  a blow 
to  the  lever,  h.  Thus  the  marker,  m,  is  made  to  depart  from  the 
uniform  spiral  it  was  describing.  When  the  current  is  restored 
the  keeper  is  attracted,  and  thus  the  marker,  m,  is  brought  back, 
which  continues  to  trace  its  spiral  as  if  nothing  had  happened. 
E'  is  connected  with  the  clock,  and  its  marker,  m',  records  the 
seconds.  E is  connected  with  the  screen,  and  records  the  passage 
of  the  projectile  through  the  screens.  By  comparing  the 
marks  made  by  m m'  the  exact  velocity  of  the  projectile  can  be 
calculated  at  all  points  of  its  course. 

The  slide.  L,  is  flxed  paralled  to  F,  and  the  cylinder,  K,  by  the 
brackets,  G II.  Y is  a screw  for  drawing  back  the  wheel-work, 
M ; and  J,  a stop  to  regulate  the  distance  between  M and  B.  The 
depression  of  the  lever.  A,  raises  the  two  springs,  5,  which  act  as 
levers,  and  bring  the  diamond  points,  m m' , down  upon  the  paper. 


,^70  NAVAL  ORDNANCE  AND  GUNNERY. 

When  an  experiment  is  to  be  made,  care  is  taken  to  see  that 
the  two  currents  are  complete.  The  fly-wheel,  A,  is  set  in  motioji 
by  hand,  so  as  to  make  about  three  revolutions  in  two  seconds. 
The  markers,  m m' , are  brought  down  upon  the  paper,  and  after 
four  or  flve  beats  of  the  clock  the  signal  to  tire  is  given,  so  that 
in  about  ten  seconds  the  experiment  is  completed  and  the  in- 
strument is  ready  for  another.  Tlie  pendulum  of  a half-seconds 
■clock  strikes  once,  each  double-beat  a very  light  spring,  and  so 
interrupts  the  galvanic  current  in  E'  once  a second. 

1300.  The  Targets. — Fig.  293  gives  the  details  of  the  screen. 

It  represents  a piece  of  hoard 
1 inch  thick  and  6 or  7 
inches  wide,  and  rather  larger 
than  the  width  of  the  screen 
to  be  formed.  Transverse 
grooves  are  cut  at  ecpial  dis- 
tances, something  less  than 
the  diameter  of  the  projectile. 
Staples  of  hard  brass  spring- 
wire  are  flxed  with  their  prongs 
in  the  continuation  of  the 
grooves.  Pieces  of  sheet  copper,  ace,  are  provided,  having 
two  elliptical  holes  the  distance  of  whose  centres  ecjuals  the  dis- 
tance of  the  grooves.  The  pieces  of  copper  are  used  to  connect 
each  wire  staple,  J,  d,  f,  with  its  neighbor  on  each  side. 
These  copper  connections  hold  down  the  wire  springs,  which, 
when  free,  are  in  contact  with  the  tops  of  the  holes  ; hut  when 
properly  w’eighted,  they  rest  on  the  lower  edge  of  the  holes. 
Thus  the  copper  c forms  a connection  between  the  staples  h and 
d \ the  copper  e joins  d and/",  and  so  on. 

^ A galvanic  stream  will  therefore  take  the  following  course, 
whether  the  springs  he  weighted  or  unweighted  : copper  a, 
brass  1)  ; copper  c,  brass  d ; copper  <?,  brass/’,  etc.  The  current 
will  only  he  interrupted  when  one  or  more  threads  have  been 
cut  and  the  corresponding  spring  is  flying  from  the  bottom  to 
the  top  of  its  hole.  About  one-flftieth  of  a second  is  recpiired 
for  the  complete  registration  of  such  aji  interruption,  the  spring 
traversing  about  ha^f  an  inch. 

The  shelf,  A (Fig.  293),  is  placed  for  the  weights  to  rest 
against,  partly  to  prevent  them  from  being  carried  fonvard  Iw 
the  projectile,  but  chiefly  to  prevent  the  untwisting  of  the 
threads  which  support  the  weights.  The  weights  used  are 
about  2 lbs.  each,  and  the  strength  of  the  sewing-cotton  for  sup- 
porting them  is  equal  to  a stress  of  about  3 lbs.,  which  is  sutii- 


ELECTRO-BALLISTIC  MACHINES. 


471 


cient  to  withstand  a tolerably  strong  wind.  As  the  weights  are 
equal  the  threads  are  kept  equally  stretched. 

1301,  Arrangement  of  Screens  for  an  experiment  is  shown 
in  Fig.  294.  The  wires  for  conveying  the  galvanic  current  are 
like  the  common  tele- 
graph-wires carried  on 
posts,  ah  G d ef  ^ A is  a 
continuous  piece  of  wire, 
and  the  current  is  made 
to  circulate  through  the 
screens.  The  ends,  a A, 
are  connected  with  the  in- 
strument and  battery.  The  projectile,  being  fired  through  the 
screens,  in  passing  cuts  one  or  more  threads  at  each  screen,  so 
that  corresponding  to  the  instant  at  whicli  the  projectile  passes 
each  screen  there  is  an  interruption  of  the  galvanic  current  and 
a simultaneous  record  on  the  paper. 

1302.  The  I^oble  Chronoscope. — The  principle  of  action  of 
this  instrument  consists  in  registering,  by  means  of  electric  cur- 
rents upon  a recording  surface,  travelling  at  a uniform  and  very 
high  speed,  the  precise  instant  at  which  a projectile  passes  cer- 
tain defined  points  in  the  bore.  (Fig.  295.) 


It  consists  of  two  portions  : firstly,  the  mechanical  arrange- 
ment for  obtaining  the  necessary  speed  and  keeping  that  speed 


472 


NAVAL  ORDNANCE  AND  GUNNERY. 


uniform  ; secondly,  the  electrical  recording  arrangemeyd.  The 
first  part  of  the  instrument  consists  of  a series  of  thin  metal 
disks,  A A,  each  33  inches  in  circumference,  fixed  at  intei-vals 
upon  a horizontal  shaft,  S S,  which  is  driven  at  a high  speed  by 
a heavy  descending  weight,  B,  through  t a train  of  gearing  multi- 
plying G25  times.  The  driving-weight  is,  during  the  experiment, 
continually  moved  up  hy  means  of  the  handle,  H.  If  the 
requisite  speed  of  rotation  were  got  up  by  the  action  of  the  fall- 
ing-weight alone,  a considerable  waste  of  time  would  ensue ; 
to  obviate  this  inconvenience,  the  required  velocity  can  be  ob- 
tained wuth  great  rapidity  by  means  of  the  handle,  C. 

1303.  The  precise  rate  of  the  disks  is  obtained  by  means  of 
the  stop-clock,  D,  wdiich  can  at  pleasure  be  connected  or  discon- 
nected with  the  revolving  shaft,  E,  and  the  time  of  making  any 
number  of  revolutions  of  this  shaft  can  be  recorded  with  ac- 
curacy to  the  one-teutli  part  of  a second.  The  speed  usually 
attained  in  working  this  instrument  is  about  1,000  inches  per 
second,  linear  velocity,  at  the  circumference  of  the  revolving 
disks,  so  that  each  inch  travelled  at  that  speed  represents  the 
one-thousaiitli  part  of  a second  ; and,  as  the  inch  is  subdivided 
by  the  vernier,  V,  into  a thousand  parts,  a linear  representation 
at  the  circumference  is  thus  obtained  of  intervals  of  time  as 
minute  as  the  one-mill  ion th  part  of  a second. 

1304.  As  a small  variation  in  speed  would  affect  the  relation 
between  the  several  records  obtained,  the  uniformity  of  rota- 
tion is  ascertained  on  each  occasion  of  experiment  by  three  ob- 
servations : one  immediately  before,  one  during,  and  one  imme- 
diately after  the  experiment,  the  mean  of  the  three  observations 
being  taken  for  the  average  speed.  AVith  a little  practice  there 
is  no  difficulty  in  arranging  the  instrument  so  that  the  disks 
may  rotate  either  uniformly  or  at  a rate  very  slowly  increasing 
or  decreasing. 

1305.  The  arrangements  for  obtaining  the  electrical  records 
are  as  follows  : the  revolving  disks  are  covered  on  the  edge  with 
a strip  of  white  paper,  and  are  connected  with  one  of  the  secon- 
dary wires,  G,  of  an  induction-coil.  The  other  secondary  wire, 
II,  carefully  insulated,  is  brought  to  a discharger,  I,  opposite 
the  edge  of  its  corresi^onding  disk,  and  is  tixed  so  as  to  be  just 
clear  of  the  latter.  AVheu  a spark  passes  from  the  discharger  to 
the  disk,  a minute  hole  is  perforated  in  the  paper  covering  upon 
that  part  of  the  disk  which  was  opposite  the  discharger  at  the 
instant  of  the  passage  of  the  spark  ; but  as  the  situation  of  this 
hole  in  the  paper  would  be  very  diffieidt  to  tind,  on  account  of 
its  extreme  minuteness,  the  paper  is  previously  coated  with 
lamp-black,  and  the  position  of  the  hole  is  thus  readily  seen  ; a 


ELECTRO-BALLISTIC  MACHETES. 


473 


distinct  white  spot  is  left  on  the  blackened  paper,  the  lamp-black 
at  that  point  having  been  burnt  away  by  the  spark,  so  that  the 
white  paper  is  shown  beneath.  By  means  of  the  micrometer  the 
distance  between  the  sparks  on  the  disks  is  read  off. 

1306.  In  order  to  connect  the  primary  wires  of  the  induc- 
tion-coils with  the  bore  of  the  gun,  so  that  they  may  be  cut  by 
the  projectile  in  its,  passage,  the  gun  is  tapped  in  a number  of 
places  for  the  reception  of  hollow  steel  plugs  carrying  at  the  end 
next  the  bore  a cutter  which  projects  slightly  into  the  bore. 
This  cutter  is  held  in  position  by  the  primary  wire,  which  is 
carefully  insulated  and  passed  down  the  plug,  through  the  cut- 
ter, and  back  out  of  the  plug,  the  ends  being  connected  to  the 
main  wires  leading  to  the  induction-coils.  When  the  projectile 
reaches  the  point  where  the  plug  is  screwed  in,  it  presses  the 
cutter  in  flush  with  the  bore,  and,  by  so  doing,  cuts  the  primary 
circuit.  As  each  plug  is  reached  a spark  is  delivered,  and  thus 
the  passage  of  the  projectile  along  the  bore  is  recorded  at  regu- 
lar intervals. 

Some  idea  maybe  conveyed  of  the  minute  inteiwals  of  time 
which  can  be  measured  by  this  means,  from  the  fact  that  the 
distances  between  the  parts  of  a X-ineh  gun  at  which  the  time 
records  have  been  obtained  are  in  some  instances  only  2.4 
inches,  while  the  total  time  the  projectile  takes  to  reach  the 
muzzle  of  the  gun — a distance  of  100  inches — when  fired  with  a 
full  charge,  is  about  the  one-hundredth  part  of  a second. 

By  this  means  the  time  may  be  recorded  which  the  projectile 
occupies,  from  the  commencement  of  motion,  in  reaching  differ- 
ent parts  of  the  bore,  and  from  these  time  records  may  be  de- 
duced the  velocity  with  which  the  projectile  is  passing  through 
the  different  parts  of  the  bore,  and  the  pressures  in  the  gun 
which  correspond  to  these  velocities. 

1307.  The  Electkic  Clepstdea^^. — Generally,  with  chron- 
ometric  instruments,  the  time  is  deduced  from  the  space  passed 
over  during  the  interval  to  be  measui’ed,  by  a body  which  moves 
according  to  a determined  law.  This  moving  body,  which  we 
call  “ chronometer,”  is  the  important  part  of  the  appaiatus  ; the 
other  fittings  are  but  accessories  serving  to  put  the  chronometer 
in  operation ; that  is  to  say,  to  render  it  capable  of  marking  the 
commencement  and  the  end  of  the  time  to  be  measured. 

The  choice  of  chronometer,  then,  is  of  first  importance. 
A weight  falling  freely  constitutes,  incontestably,  the  most  sim- 
ple and  most  exact  chronometer;  regulated  by  an  immutable 
law  of  nature,  its  motion  is  accomplished  without  the  aid  of  any 

* Naval  Ordnance  Papers,  No.  4 Translated  by  Lieutenant-Commander 
J.  D.  Marvin,  U.  S.  Navy. 


4:74 


NAVAL  ORDNANCE  AND  GUNNERY. 


ELECTRO-BALLISTIC  MACHINES.  475 

intermediary  force ; neither  use  nor  time  can  alter  its  rate ; it 
is  absolutely  invariable. 

Unfortunately,  this  chronometer  is  only  applicable  to  the 
measure  of  times  relatively  short,  for  the  extent  of  fall  increases 
with  the  time  in  very  rapid  proportions. 

One  can,  it  is  true,  transform  the  vertical  fall  into  a move- 
ment of  rotation,  whether  continuous,  such  as  that  of  revolving 
cylinders,  or  alternate,  such  as  that  of  pendidums ; but  in  both 
cases  the  great  advantage  of  a constant  chronometric  movement 
is  lost ; account  must  then  he  taken  of  friction,  and  this  may  be 
varied  by  causes  which  escape  the  observation,  and  certainty 
and  reliability  in  the  result  no  longer  exist.  In  order  to  avoid 
this  inherent  inconvenience  in  the  employment  of  such  a me- 
chanical instrument,  we  may  employ  as  a chronometer  the  flow 
of  a liquid,  and  determine  the  time  by  means  of  the  weight  run 
out  during  the  interval  to  be  measured.  For  this  purpose  mer- 
cury presents  itself  naturally  to  the  mind ; this  metal,  very 
fluid  and  homogeneous,  has  great  specific  weight ; its  evapora- 
tion is  insensible,  and,  not  moistening  the  inclosing  sm’faces, 
its  use  is  extremely  clean  and  convenient. 

This  has  been  done  by  Major  La  Boulenge  of  the  Belgian 
Artillery,  in  an  instrument  to  which  he  has  given  the  name  of 
Electric  Clepsydra. 

1308.  Description  of  the  Instrument. — It  is  composed 
(Fig.  293)  of  a circular  reseiwoir.  A,  of  0“.20  diameter 
by  0“.03  high,  containing  mercury,  and  supported  by  a hollow 
central  column,  B,  of  0™.20  height,  terminating  in  a tripod 
fitted  with  levelling-screws  X.  This  vessel,  of  cast-iron,  rests 
on  a circular  plate,  C,  of  the  same  metal,  which  is  fitted  with  a 
rim  to  catch  the  mercury  which  may  through  inadvertence  flow 
out  of  the  receiver,  D.  A disk  of  cast-iron,  E,  covers  the  reser- 
voir and  bears  the  electrical  fittings  of  the  apparatus.  The  hol- 
low column,  which  makes  a part  of  the  receiver,  terminates  at 
the  lower  end  in  a fine  orifice,  above  which  is  fitted  a conical 
valve,  which  prevents  the  mercury  from  running  out.  The 
face  of  the  orifice,  the  body  of  the  valve,  li,  and  its  seat,  F,  are 
of  steel. 

A rigid  stem,  G,  connected  by  a swivel-joint  to  the  body  of 
the  valve,  rises,  following  the  axis  of  the  receiver,  traverses  a 
central  opening  in  the  upper  disk,  and  then  connects  above  this 
latter  to  a horizontal  lever,  H,  which  is  called  the  valve-lever. 
If  the  arm  of  this  lever  opposite  to  the  connection  of  the  stem 
be  pressed  down,  the  valvm  is  opened  and  flow  is  produced.  If 
the  effort  be  discontinued,  the  valve  falls  back  upon  its  seat,  and 
the  flow  is  arrested  instantaneouslv. 


476 


NAVAL  ORDNANCE  AND  GUNNERY, 


1309.  The  opening  and  closing  of  the  valve  are  performed 
by  the  action  of  two  levers,  I and  J,  which  fall  successively,  and 
of  which  the  heavier  extremities,  fitted  with  armatures  of  soft 
iron,  K and  L,  are  held  in  the  state  of  “ ready  ” (shown  in  the 
figure)  by  electro-magnets,  M and  N.  The  lever  for  closing  is 
formed  of  two  parallel  arms,  united  at  one  end  by  the  armature, 
at  the  other  by  a cross-piece  used  to  raise  the  lever,  K ; this 
disposition  permits  it  to  move  without  touching  the  valve-lever. 

If  the  current  which  actuates  the  electro-magnet  M be 
broken,  the  opening  lever  falls  upon  the  end  of  the  valve-lever, 
opens  the  valve  permanently,  and  the  mercury  fiows  into  the 
receiver,  D,  placed  immediately  under  the  orifice.  "We  call  the 
lever  K,  opening-lever ; its  magnet  current  and  circuit  will  be 
called  by  the  name  of  electro-magnet  current  and  circuit  of  open- 
ing, to  distinguish  them  from  similar  fittings  which  operate 
the  closing.  If  the  second  current  be  broken,  the  closing-lever 
falls  in  turn,  raises  the  opening-lever  to  its  original  position  ; 
then  the  lever  of  the  valve  being  freed,  this  latter  falls  back 
into  its  seat,  and  the  flow  is  arrested. 

A catch,  T,  prevents  vibration  of  the  closing-lever  after  its 
fall.  This  simple  combination  of  three  levers  fulfils  perfectly 
the  mechanical  conditions  imposed,  for  the  valve  opens  suddenly 
by  a shock,  while  it  closes  freely  by  its  own  action. 

In  actual  practice  the  two  cun-eiits  are  broken  successively 
by  the  projectile,  a weight,  P',  of  mercury  flows  into  the  re- 
ceiver, and  it  is  required  to  deduce  from  it  the  period  which  has 
separated  the  two  ruptures. 

1310.  Let  us  suppose  for  a moment  that  the  apparatus  fur- 
nishes a constant  flow,  and  let  P be  the  flow  of  the  orifice,  that 
is,  the  weight  of  mercury  which  flows  per  second ; by  dividing 
P'  by  P,  the  time  is  obtained  which  has  elapsed  between  the 
instant  of  opening  and  that  of  closing  the  valve. 

p 

The  relation  pwill  also  give  the  time  which  has  elapsed  be- 
tween the  rupture  of  two  currents,  if  the  valve  has  opened  and 
closed  at  the  precise  instant  of  the  rupture  of  the  corresponding 
current.  Put  this  is  not  the  case;  when  the  first  current  is 
broken,  a certain  time  is  necessary  in  order  that  the  nuignet 
may  arrive  at  such  a state  of  demagnetization  as  to  release  the 
armature,  then  a certain  time  for  the  fall  of  the  lever,  and 
finally  an  additional  time  for  the  complete  raising  of  the  valve. 
Analogous  periods  transpire  between  the  rupture  of  the  clos- 
ing current  and  the  arrest  of  the  flow.  The  determination 
of  these  short  periods  is  obviated  by  applying  to  the  instru- 
ment the  method  of  simultaneous  disjunction,  the  import- 


ELECTBO-BALLISTIC  MACHINES, 


477 


ant  feature  of  which  has  been  devised  by  Major  Kavez.  To 
this  end  the  fall  of  the  levers  is  regulated  in  such  a way  that 
the  opening-lever  occupies  less  time  than  the  other,  from  the 
commencement  of  its  fall  to  its  action  on  the  valve.  Thus, 
when  by  means  of  a disjunctor  both  currents  are  cut  at  the 
same  time,  the  first  lever  opens  the  valve  a certain  time  before 
the  second  closes  it ; the  weight,  P,  of  mercury  run  out  in  this 
way,  is  the  precise  quantity  to  be  deducted  from  P',  in  order  to 

P' — p 

obtain  from  the  expression — 73-^5  the  time  which  has  elapsed 


between  the  rupture  of  the  two  currents. 

This  method  of  procedure  takes  into  account  both  the  time 
lost  in  the  working  of  the  mechanism  and  that  of  demagnetiza- 
tion, which  varies  with  the  respective  force  of  the  two  cur- 
rents. 

1311.  The  disjunctor  is  the  same  as  that  which  has  been 
adopted  for  Le  Boulenge’s  chronograph.  It  is  composed  (Fig. 
297)  of  a bent  spring,  t,  the  free  end  of  which  is  caught  by  a 
catch,  X,  when  it  is  pressed  down  by  bearing  on  the  button,  0. 
In  this  position  it  permits  two  thin  plates  of  steel,  q and  y',  to 
bear  upon  the  conducting-pins,  r and  /,  and  closes  by  this  con- 
tact the  two  circuits.  If  the  catch  be  released,  the  spring  rises 
suddenly ; its  cross-piece,  covered  with  an  insulating-plate  of 
ivory,  raises  the  two  plates,  q and  3’',  and  breaks  the  currents. 
The  two  pins,  r and  t' , are  fitted  with  a screw  thread,  and  thus 
provide  for  the  adjustment  of  the  height  of  the  two  plates, 
so  that  they  may  be  raised  at  the  same  time  by  the  spring. 
The  head  of  the  screw,  y>,  limits  the  play  of  the  spring ; the 
bottom  surface  of  the  disjunctor  is  covered  with  a sheet  of 
India-rubber,  for  the  purpose  of  deadening  the  vibrations,  which 
permits  it  to  be  set  up  on  the  same  table  as  the  instrument. 

Experience  has  proved  that  this  disjunctor  is  without  fault ; 
once  regulated,  it  is  not  liable  to  be  deranged ; its  regularity  is 
perfect,  for  with  the  chronograph  it  gives  identical  disjunctions, 
and  as  to  its  exactitude  it  can  be  verified  whenever  desired,  by 
establishing  that  inversion  of  the  currents  does  not  produce  any 
change  in  the  disjunction. 

1312.  Basis  of  the  Calculation  of  the  Times. — We  will 
now  explain  how  the  time  is  deduced  from  the  weight  of  mer- 
cury run  out. 

We  have  supposed  the  flow  constant;  but  it  is  not  so  in 
reality,  for  in  proportion  as  the  liquid  runs  out  the  height  of  the 
level  diminishes,  and  with  it  the  discharge.  In  order  that  the 
flow  may  always  commence  under  the  same  conditions,  before 
each  trial  the  mercury  is  brought  to  a fixed  level,  which  is  done 


478 


NAVAL  ORDNANCE  AND  GUNNERY. 


by  a very  simple  operation.  For  this  purpose,  the  instrument 
being  levelled  by  means  of  an  air-bubble  level,  whicli  is  laid  in 
two  directions  at  right  angles  to  each  other  on  the  upper  disk, 
a fresh  quantity  of  mercury  is  added  to  that  in  the  receiver ; 
then  an  overflow  is  opened  (called  level-escajpe)  formed  by  a 
simple  screw,  o.  The  orifice  being  opened,  the  excess  runs  out 
into  a little  bucket,  s,  hung  under  the  level-escape. 

The  level  thus  obtained,  which  we  will  call  the  original 
level,  is  always  of  the  same  height ; for  the  determining  experi- 
ments show  that  in  the  first  unit  of  time  the  same  Amlume 
always  runs  out.  But  the  weight  of  this  volume  will  vary 
with  the  temperature ; consequently,  to  reduce  all  experi- 
ments to  the  same  terms,  each  weighing  must  be  brought 
to  a uniform  temperature.  They  are  reduced  to  0°  by  the 
formula  = P ( 1 -|-  « t\  a being  the  coefficient  of  the  ex- 
pansion of  mercury,  0”.00018,  and  t the  temperature  of  the 
receiver.  This  temperature  is  indicated  by  a thei’mometer, 
which  forms  a part  of  the  apparatus,  the  bulb  of  which  is  im- 
mersed in  the  mercury-reservoir  by  passing  it  through  an  open- 
ing, U,  in  the  upper  disk. 

Tlie  rapidity  of  flow  will  vary  at  each  instant  by  reason  of 
the  lowering  of  the  level,  but  on  account  of  the  great  surface  of 
the  receiver  as  compared  with  that  of  the  orifice,  this  lowering 
during  the  interval  of  a second  is  very  small  (about  one-tenth 
of  a millimetre,)  and  the  time  may  be  calculated  without  errors 
in  the  results  by  supposing — 

1.  That  the  flow  is  constant  during  the  interval  of  one 
second. 

2.  That  in  passing  from  one  second  to  another,  the  amount 
of  flow  decreases  by  a constant  quantity. 

1313.  We  will  support  this  method  of  calculation  by  an  ex- 
ample, the  data  for  which  are  given  by  the  instrument  itself. 

Let  II  be  the  height  of  the  original  level  above  the  orifice, 
and  P the  weight  run  out  during  tlae  first  second.  At  the  end 
of  this  time  the  level  will  have  been  lowered  by  a quanity.  A, 
which  will  be  the  altitude  of  a cylinder  having  for  a base  the 

"P 

surface  of  the  upper  reservoir,  and  for  volume—,  d being  the 
density  of  mercury,  13.598. 

We  shall  have  then  h = — R being  the  radius  of  the 

;r  li  0 ° 

reservoir. 

At  the  beginning  of  the  second  second  the  height  of  the 
level  will  be  H'  II  — A. 

Let  us  call  A the  surface  of  the  orifice,  and  m the  co- 


- ELECTRO-BALLISTIC  MACHINES. 


479 


efficient  of  the  contraction  of  the  stream,  we  will  have,  by  the 
laws  of  hydraulics — _ 

P = m A 

Since  from  second  to  second  the  level  falls  only  by  an  almost 
inappreciable  fraction,  the  coefficient,  m,  will  not  change,  and 


Fiff.  297. 


we  shall  have  also  the  weight  run  out  during  the  second  second, 
P'  = m A fTylP- 

j fj7 

Consequently  -r.  / -o- 


P'=  P 


H 


is  the  formula  which  enables  us  to  calculate  the  weight  of  the 
second  second ; that  of  the  first,  the  height  of  the  original 
level,  and  the  radius  of  the  reservoir  being  known. 


480 


NAVAL  OEDNANCE  AND  GUNNEET. 


Having  calculated  P',  we  may  deduce  from  it  in  the  same 
way  V"  Y'",  etc.,  the  weights  run  out  during  the  thii-d,  fourth, 
and  following  seconds. 

The  data  given  by  the  instmment  are  H = 0”.  20,  P =:  0™. 
10,  and  P = 6200  centigrammes." 

1314.  Applying  these  values  to  the  preceding  calculation, 
we  have  the  following  results  : 


Seconds. 

Height  of  Level. 

Discharge. 

1st.  Dif. 

2d.  Dif. 

First 

Millimitrea. 

0.  2000C0000000 

CentigrammeH. 
6200.  000000 

Centgr, 

2.250042 

Centgr. 

Second 

0.  199854862317 

6197.  749958 

2.  250032 

0.  000011 

Third 

0. 199709777705 

6195.  499927 

2.  250020 

0.  000011 

Fourth 

0.  199564745545 

6193. 249907 

2.  250008 

0.  000012 

Fifth 

0.  199419766096 

6190. 999899 

2.  249995 

0.  000D13 

Sixth 

Seventh 

0.  199274839298 
0. 199129965171 

6188.  749904 
6186.  499922 

2.  249982 

0.  000013 

The  figures  of  this  table  prove  that  it  is  permissible  to  con- 
sider the  difference  of  weis:hts  run  out  from  one  second  to  an- 
other  as  absolutely  constant. 

The  column  of  second  differences  shows,  in  effect,  that  they 
are  so,  to  nearly  the  ten-millionth  of  a gramme,  or  in  time 

^ or  0^'.000000002,  a quantity  ten  thousand  times 

smaller  than  the  fraction  of  time  which  we  can  hope  to  measure 
in  practice. 

In  the  second  place,  the  difference  between  the  weights  run 
out  in  two  consecutive  seconds  being  but  2'.25,  which  represents 
in  time  0'h0003,  no  appreciable  error  is  committed  in  calculat- 
ing the  time  as  though  the  flow  were  constant  duriiig  the  in- 
terval of  one  second. 

1315.  In  order  to  compute  the  table  of  times  of  the  clepsy- 
dra according  to  the  principles  indicated,  it  will  be  seen  that 
we  must  know  the  height  of  the  original  level.  Owing  to  the 
convex  curve  formed  by  the  mercury,  it  is  very  difficult  to 
measm-e  this  height  exactly,  but  fortunately  tiffs  exact  measure 
is  unnecessary,  as  will  be  shown.  The  weight  of  the  first  sec- 
ond being  6,200".00,  we  have,  by  supposing  H = 0 .200,  found 

* In  the  use  of  the  instrument  the  centigramme  is  adopted  as  the  unit  of 
weight. 


ELECTEO-BALLISTIC  MACHINES. 


481 


for  the  second,  6,197'.T5.  Suppose  that  in  the  measurement 
of  H a mistake  of  a millimetre  is  made,  and  that  in  reality 
H = 0“.201,  the  weight  of  the  second  second,  calculated  with 
this  new  value,  would  be  6197.76  ; 


for  H = 0“.202  it  would  be 6197.77 

for  H = 0.203  it  woidd  be 6197.78 

for  H = 0.204  it  would  be 6197.79 


That  is  to  say,  an  ei’ror  of  a millimetre  in  the  measurement 
of  H brings  into  the  calculation  of  the  second  second  only  an 
error  of.  0'b000002,  a quantity  which  can  clearly  be  neglected 
in  practice. 

1316.  Experimental  Determination  of  the  Table  of  Times. 
— In  order  to  determine  experimentally  the  weight  of  mer- 
cury which  runs  out  in  the  first  second,  the  two  currents 
of  the  apparatus  must  be  broken  at  intervals,  separated  by 
exactly  one  second.  A first  method  would  consist  in  pass- 
ing the  current  through  a plate  rheotome^  which  we  will 
describe  farther  on,  and  by  bearing  on  the  plates  in  fol- 
lowing the  beats  of  a seconds  pendulum.  From  the  weight 
obtained  we  would  subtract  the  weight  of  disjunction,  and 
thus  have  the  weight  of  the  first  second.  But  by  this  method 
even  a very  experienced  operator  could  never  obtain  in 
his  observations  the  precision  of  which  the  instrument  is  sus- 
ceptible ; for  this  reason,  a more  exact  method  has  been  sought 
out,  which  consists  in  causing  the  currents  to  be  broken  by  the 
pendulum  itself,  which  divests  the  process  of  all  personal  skill. 
A system  of  two  small  metallic  circuit-closers,  ab  c and  d ef 
(Fig.  299),  are  fastened  to  the  lower  part  of  the  case  of  a 
seconds-beating  regulator,  and  in  the  vertical  plane  of  the  pen- 
dulum. Each  of  these  closers  is  movable  around  an  axis,  b and 

perpendicular  to  the  plane  of  oscillation.  The  pendulum 
terminates  in  a cutter,  O,  which,  meeting  in  its  course  the  points 
of  the  closers,  causes  them  to  fall  alternately  to  the  right  and  to 
the  left  of  their  respective  vertical  positions.  Let  ? s be  the 
opening  circuit,  and  let  a point,  of  this  circuit  be  united  by  a 
conductor  to  the  connection  Ti,  and  a point,  p to  the  connec- 
tion 1. 

1317.  The  base,^y>,  which  supports  the  whole  system  is  in- 
sulated, but  the  connection  h communicates  through  metal  with 
the  axis  b,  and  the  connection  I with  the  screw  g / consequently, 
when  the  pendulum  is  at  m m,  that  is  to  say,  at  the  end  of  its 
beat  to  the  left,  the  closer  ab  c being  in  contact  with  the  screw 
<7,  the  diverted  circuit,  r hi  gf\^  complete.  If  in  this  state  of 
things  the  circuit  be  cut  in  the  part  g r,  the  opening  current 
will  not  be  destroyed ; it  will  pass  entirely  by  the  diversion 

31 


482 


NAVAL  ORDNANCE  AND  GUNNERY. 


r Tcl  q,  but  the  pendulum  continuing  its  course  will  destroy  the 
continuity  of  the  diversion,  and  consequently  the  opening  cur- 
rent, at  the  instant  when,  arrived  at  z z,  it  touches  the  arm  c. 
It  must  be  remarked  that  so  long  as  the  circuit  between  q and  r 
is  not  interrupted,  the  movement  of  the  pendulum  cannot 
break  the  current.  Let  an  analogous  diversion,  xij  v,  be  es- 
tablished by  means  of  the  closer  d ef,  in  the  closing  circuit 
u y.  The  pendulum,  having  arrived  at  ml  m',  will  have  met 
the  army,  pressed  dowm  the  closer  d upon  its  screw  of  con- 


tact, A,  and  closed  the  diversion  of  the  closing  current.  If  at 
this  instant  a rupture  be  made  between  v and  x,  the  closing  cir- 
cuit will  not  be  broken  ; but  this  rupture  will  take  place  when 
the  pendulum,  arriving  at  z'  z',  touches  the  arm  d. 

1318.  It  is  apparent,  then,  that  the  operator  can  break  the 
opening  current  by  means  of  the  pendulum,  when  it,  in  passing 


ELECTRO-BALLISTIC  MACHINES. 


483 


to  the  left,  arrives  on  tlie  line  z z,  and  in  the  same  way  he  can 
break  the  closing  current  at  the  moment  when  the  pendulum 
coming  to  the  right,  arrives  on  the  line  z'  z' . To  accomplish 
the  breaking  of  the  circuits  g’  r and  -y  a rheotome  (Fig.  298) 
is  used  having  two  plates,  A and  B,  which  close  the  circuits  by 
their  contact  with  C and  D.  These  contacts  established,  the 
opening  current  passes  at  the  same  time  through  the  general 
circuit  t q K r s,  and  through  the  diversion  qlic  r,  which  in- 
cludes the  contact  of  the  closer.  If  the  finger  he  pressed  on 
the  extremity,  E,  of  the  plate  A,  the  general  circuit  is  inter- 
rupted between  q and  and  the  closing  current  passes  as  a 
whole  through  the  diversion.  The  same  effect  is  produced  in 
the  closing  circuit  by  means  of  the  plate  B.  The  circuits  be- 
ing established  in  the  manner  which  has  just  been  explained, 
and  the  clepsydra  being  in  readiness,  that  is  to  say,  the  mercury 
at  the  level-mark  and  the  two  levers  raised,  the  operator  follows 
with  the  eye  the  movement  of  the  pendulum.  When  he  has 
taken  up  the  cadence  accurately,  he  places  the  forefinger  on  E 
when  the  pendulum  is  nearly  in  the  position  m m ; then  the 
pendulum,  arriving  at  z s,  breaks  the  opening  current,  and  the 
running  out  commences.  Toward  the  end  m'  ml  of  the  same 
oscillation,  the  operator  presses  down  the  second  plate,  B,  and 
the  pendulum,  repassing  to  z'  z\  breaks  the  closing  current,  and 
the  flow  is  arrested.  Let  us  call  a the  weight  of  mercury  ob- 
tained by  this  operation,  and  /J  that  which  would  have  been 
obtained  if  the  two  currents  had  been  broken  at  exactly  the 
same  instant ; then  a — f3  will  be  the  weight  run  out  while  the 
pendulum  is  passing  over  the  angular  space  z m' m' z' . 
This  space  will  correspond  exactly  to  one  second,  if  the  two 
oblique  lines  z z and  z'  z'  are  equidistant  from  the  vertical ; 
but  this  condition  is  realized  with  difficulty  in  practice,  and  if 
we  were  to  bind  ourselves  to  its  acceptance,  the  process  would 
he  subject  to  serious  errors ; therefore  we  have  made  the 
process  independent  of  it,  by  proceeding  in  the  following 
way: 

1319.  After  having  obtained  the  weight  or,  as  has  just  been 
explained,  the  mercury  is  again  raised  to  the  level-mark,  and  the 
instrument  put  in  readiness ; then  the  operation  is  recom- 
menced, but  a longer  time  is  measured.  After  having  broken 
the  first  current,  the  second  is  not  ruptured  at  the  end  of  the 
oscillation ; on  the  contrary,  the  pendulum  is  allowed  to  return, 
and  it  is  not  until  its  arrival  for  the  second  time  at  m!  m'  that 
the  second  plate,  B,  is  pressed  down.  Let  y be  the  w'eight  ob- 
tained in  this  second  operation  y — /3  will  be  the  w'eight 
which  runs  out  while  the  pendulum  is  passing  over  zm!  -\-m! 


m 


NAVAL  OKDNANCE  AND  GUNNEEY. 


z'  3' m m m'  m'  z’ . If  from  tire  time  (;^  — /?)  we  sub- 
tract the  time  («  — /3)  which  is  required  by  the  pendulum  to 
pass  over  z m'  -\-m!  z\  there  will  remain  y — a,  which  will  be 
the  time  employed  by  the  pendulum  to  pass  over  the  space 
{z  m'  m'  z'  z' m ^ m m'  m'  z')—{z  m!  -f-  mf  z')  or  z' m 
m mf  m'  z'  ^ m m\  that  is  to  say,  two  complete  oscilla- 


tions, and 


Y — 


-will  be  the  weight  run  out  in  one  second. 


By  this  method  we  obviate  the  determination  of  the  weight 
/?,  corresponding  to  a simultaneous  disjunction.  The  electrical 
conditions  not  varying  from  one  trial  to  another,  this  weight 
will  remain  the  same,  and  since  it  is  included  in  each  of  the 
above  partial  operations,  it  is  eliminated  by  the  subtraction. 


ELECTRO-BALLISTIC  MACHINES. 


485 


1320.  Knowing  the  weight, 


of  one  second,  we  can  cal- 


culate the  weight  of  the  following  by  the  process  which  has 
been  explained,  and  we  will  discover  in  consequence  the  con- 
stant ditference  oj,  from  one  second  to  another.  These  two 
quantities  suffice  for  calculating  the  weights  P,,  Pj,  P3,  P4,  P„, 
corresponding  to  the  1'‘,  2%  S'*,  4“*,  tz,***  second.  Let  it  be  re- 
marked, first,  that  the  system  of  closers  being  established  as  far 
as  possible  in  the  vertical  plane  of  the  pendulum,  the  weight 
y — /?  will  be  very  nearly  that  which  runs  out  during  the  first 
three  seconds. 

a — /?  will  in  the  same  way  be  the  weight  of  the  first  sec- 
ond ; consequently  the  weight  y — a will  be  that  which  flows 
during  the  second  and  third  seconds. 

We  will  have  then — • 


P2  X P3  = (r  — 

and 

P2  — P3  = S 


whence 


-D  _ (r  — «)  + 

■O  _{r— a)  ~a> 

^ , 


The  first  second  will  be  Ps  go,  the  fourth  P3  — cq  and  the 
w'"  P,„_„  - _ 

Before  giving  the  results  furnished  by  this  process,  a re- 
mark in  relation  to  its  nse  remains  to  be  made.  The  contact 
between  the  closer  and  the  bearing-screw  not  'being  very  close, 
this  point  presents  a great  resistance  to  the  passage  of  the  cur- 
rent, and  it  often  happens  that  when  the  direct  circuit  is  cut  by 
the  rheotome,  the  current  does  not  retain  sufficient  force  to 
hold  the  armature  of  the  magnet ; it  is  for  this  reason  that  one 
should,  in  this  experiment,  give  to  the  magnets  a great  force  of 
attraction,  in  order  that  they  may  preserve  a sufficiency  when 
the  current  passes  through  the  diversion  alone. 

1321.  Use  of  the  Instrument  in  Experimental  Firing. — 
The  clepsydra  is  set  up  in  a place  in  close  proximity  to  the 
firing-ground,  and  on  the  same  table  are  placed  the  disjunc-' 
tor,  B,  and  the  balance,  C (Fig.  300).  The  batteries  are 
on  the  floor  or  elsewhere  near  by.  They  are  formed  of 
Bunsen’s  elements,  arranged  in  the  ordinary  way,  that  is, 
with  nitric  acid  in  the  porous  cup,  and  a mixture  of  sul- 
phuric acid  and  water  in  the  glass.  Two  or  tlnee  cells  gen- 
erally suffice  for  the  opening  current,  the  number  necessary  for 


486 


NAVAL  ORDNANCE  AND  GUNNERY. 


the  closing  current  varying  with  the  extent  and  resistance  of 
the  circuit.  In  certain  special  cases  Bunsen  cells,  such  as  are 
used  for  telegraphy,  have  been  employed.  In  these  cells  the 
carbon  is  replaced  by  a plate  of  copper,  riveted  to  the  zinc 
cylinder ; the  glass  contains  only  water,  and  the  porous  cup  a 
mixture  of  water  and  sulphuric  acid.  This  system  has  the  ad- 
vantage of  being  serviceable  for  two  months  without  its  being 
necessary  to  touch  it,  but  the  electro-motive  force  which  it  de- 
velops is  very  rapidly  exhausted.  When  the  current  is  allowed 
to  circulate  during  any  time,  the  battery  is  very  sensibly  weak- 
ened ; if  the  circuit  be  interrupted,  it  stores  up  a fresh  force, 
and  the  current  returns  to  its  original  intensity.  These  battei’- 
ies  are  very  irregular,  and  much  inferior  in  this  respect  to  the 
ordinary  Bunsen  batteries,  the  action  of  which  can  be  consid- 
ered constant  during  the  same  series  of  experiments. 

1322.  The  opening-circuit,  ahcdefg  (Fig.  300),  includes 
the  first  target,  the  disjunctor,  and  the  opening  electro-magnet ; 
it  passes  in  front  of  the  muzzle  of  the  gun,  whether  on  an  ordi- 
nary target-frame  placed  at  10”  from  the  muzzle,  or  in  a simple 
wire  stretched  across  the  face  of  the  muzzle.  In  this  latter  case 
it  must  be  ascertained  whether  the  wire  used  is  strong  enough 
to  resist  the  blast  of  gas  which  precedes  the  projectile. 

1323.  The  second  ch'cxxit,  hi  j him  n oj>  qr  s,  the 

second  target,  the  disjunctor,  and  the  closing  electro-magnet. 
In  the  trials  at  the  ISTaval  Experimental  Battery,  Annapolis, 
Md.,  there  is  used  in  forming  this  circuit  a telegraphic  line 
parallel  to  the  line  of  lire.  The  current  is  brought  to  the  second 
target,  h I,  by  a conductor,  i /r,  united  to  the  line  at  the  top  of 
the  target.  After  its  passage  through  the  target  the  current 
reaches  the  earth  through  a plate,  m,  thrust  into  the  ground 
near  by,  the  circuit  being  continued  by  a second  plate,  n,  planted 
near  the  location  of  the  instrument ; the  current  returns  from 
this  plate  to  the  battery  by  passing  through  the  instrument. 
By  this  arrangement,  when  the  range  is  changed,  it  suffices  to 
simply  move  the  second  target  and  its  earth-plate.  These 
plates,  which  are  formed  of  a simple  plate  of  copper  or  of  zinc 
of  a few  decimeters  long,  or  of  a coil  of  wire,  ought  to  be 
placed  either  in  water  or  in  a damp  stratum  of  soil.  If  by  the 
nature  of  the  ground  this  kind  of  soil  is  difficult  to  reach,  the 
current  should  be  retmmed  to  the  battery  by  a second  metallic 
conductor. 

1324.  All  these  dispositions  being  made,  it  is  ascertained 
whether  the  currents  pass,  and  whether  they  have  sufficient  force 
to  hold  the  levers  of  the  clepsydra  in  position. 

The  magnets  are  then  regulated  by  running  the  movable 


ELECTRO-BALLISTIC  LIACHINES. 


487 


core  more  or  less  inside  the  coil.  The  force  of  attraction  is 
regulated  so  that  the  levers  Avill  be  held  with  tlie  least  power 
necessary  to  prevent  their  being  subject  to  accidental  release. 
The  operator  then  tills  to  level  by  pouring  a cup  of  mercury 
into  a glass  funnel  placed  in  the  orifice,  Y,  and  then  opening 
the  overflow.  It  is  to  be  remarked  that  by  this  operation  the 
mercury,  which  forms  the  surface  of  the  bath,  is  drawn  from 
the  receiver,  and  this  is  the  only  portion  which  can  contain  im- 
purities. This  mercury  is  poured  into  a flannel  strainer,  from 
which  it  comes  out  freed  from  oxide  and  dust.  This  process  is 
necessary,  for  experience  has  proved  that  the  mercury  em- 
ployed ought  to  be  perfectly  clean ; it  must  then  be  improved 
in  quality  by  use  in  the  instrument,  owing  to  these  successive 
filtrations. 

1325.  To  make  ready  the  instrument,  the  currents  are  first 
made  to  circulate,  by  pressing  on  the  button  of  the  disjunctor 


I j 


until  the  spring  is  caught  in  the  catch ; then  with  the  fore- 
finger the  catcli,  T,  is  disengaged,  while  the  closing-lever  is 
brought  in  contact  with  its  magnet  by  using  the  thumb.  As 
to  the  opening-lever,  it  is  self-acting,  for  it  is  raised  against  its 
magnet  each  time  the  mechanism  operates. 

1326.  To  cause  disjunction,  the  spring  of  the  disjunctor  is 
released  by  bearing  with  the  forefinger  on  the  trigger,  x,  and 
with  the  thumb  on  the  guard,  v.  These  operations,  as  will  be 
seen,  are  extremely  simple  and  rapid;  the  principle  has  there- 
fore been  adopted  of  making  three  disjunctions  before  each 
fire,  which  requires  hardly  a half  minute.  The  mercury  being 
received  each  time  in  the  same  vessel,  the  total  weight,  divided 
by  three,  will  be  that  of  the  disjunction  obtained  by  a mean  of 
three  trials.  After  having  made  the  disjunctions,  the  original 


488 


NAVAL  ORDNANCE  AND  GUNNERY. 


level  is  not  restored  preparatory  to  the  firing,  for  the  quantity 
of  mercury  run  otf  is  too  small  to  alter,  in  a sensible  degree, 
the  height  of  the  liquid  in  the  reservoir.  At  the  instant  of 
firing,  the  levers  I and  J fall  successively,  hut  if  the  magnets 
be  regulated  too  “ fine,”  it  will  follow  that  the  shock  produced 
by  the  fall  of  the  first  lever  will  cause  that  of  the  second. 
This  effect  is  avoided  in  the  following  way : If  the  time  to  be 
measured  exceeds  one  second,  which  is  generally  the  case,  be- 
fore giving  the  order  “fire,”  the  closing-lever  is  held  against 
its  magnet  by  the  finger  until  the  opening-lever  has  fallen. 
Operating  in  this  way  in  the  measure  of  a time  less  than  a 
second,  there  would  not  be  time  to  remove  the  finger  before 
the  rupture  of  the  second  target ; therefore,  in  this  case,  suffi- 
cient force  is  given  to  the  magnet  to  prevent  its  releasing  its 
hold  when  the  first  lever  falls. 

1327.  The  weights  are  taken  by  means  of  a balance  form- 
ing a part  of  the  apparatus,  which  is  constructed  with  a view 
to  this  special  use.  For  convenience  of  transport,  it  can  be 
dismounted  and  placed  in  the  instrument-case.  This  balance 
not  being  sensitive  beyond  a half  centigram,  the  weights  are 
easily  taken.  This  degree  of  precision  is  quite  sufficient,  for 
the  half  centigram  represents  a time  less  than  the  twelve- 
thousandth  of  a second.  Immediately  after  firing,  the  disjunc- 
tion is  weighed;  then  the  discharge  during  the  passage  of  the 
shot,  and  tlie  mercury  poured  back  into  the  instrument,  restores 
the  original  level.  In  this  way  the  operation  of  levelling  need 
be  done  but  once  at  the  commencement  of  the  practice ; if, 
however,  the  temperature  changes  sensibly,  it  ought  to  be  done 
over. 

As  the  two-fold  weighing  is  quite  a long  operation,  a mon- 
grel process  is  used  which  possesses  very  nearly  the  same  ex- 
actness. In  the  experiments  the  weight  which  will  be  obtained 
is  always  approximately  known,  and  this  weight,  varying  but 
very  little  from  fire  to  fire,  a counter-balance  is  used  which 
balances  this  approximate  weight  placed  in  one  of  the  scale- 
pans  with  the  vase  in  which  the  mercury  is  to  be  weighed. 
At  each  trial  it  is  only  necessary  to  replace  the  approximate 
weight  by  the  mercury  obtained,  and  to  balance  the  scale  with 
small  weights,  which  are  the  amount  to  be  added  or  subtracted 
in  order  to  get  the  weight  sought.  In  order  to  simplify  this 
operation,  the  counter-balance  is  adjusted  for  the  minimum 
which  can  be  obtained,  and  in  this  way  the  difference  is  always 
to  be  added.  A counter-balance  is  also  used  in  weighing  the 
disjunctions.  Experience  has  shown  that,  with  a little  practice 
at  the  balancej  the  operation  of  weighing  is  easily  done  within 


INSPECTION  OF  GUNPOWDEE. 


489 


the  time  required  for  repairing  the  targets  and  the  serving  of 
the  piece. 

1328.  Force  of  Gravity. — In  the  use  of  nearly  all  electro- 
ballistic  machines,  the  force  of  gravity  enters  as  a necessary 
element  in  the  calculation.  The  following  formula*  may  be 
employed  to  calculate  the  most  probable  value  of  the  apparent 
force  of  gravity — being  the  resultant  of  true  gravitation  and 
centrifugal  force — in  any  locality  where  no  pendulum  observa- 
tions of  sufficient  accuracy  have  been  made. 

This  formula  with  the  two  coefficients  which  it  involves, 
corrected  according  to  modern  pendulum  observations,  is  as 
follows : 

Let  G be  the  apparent  force  of  gravity  on  a unit  mass  at 
the  equator,  and  g that  in  any  latitude  A : then 


The  value  of  G in  terms  of  the  absolute  unit  is  32.088. 
When  the  point  of  observation  is  materially  above  the  sea 
level,  the  true  gravity  may  be  derived  with  sufficient  accuracy 
for  all  practical  purposes  from 


in  which  g'  represents  the  force  of  gravity  at  the  height.  A, 
above  the  sea,  and  r,  the  radius  of  the  earth.  {Army  Ordnance 
Manual^  p.  469.) 

The  formulae  given  by  different  standard  authorities  will 
give  somewhat  varying  results  for  the  same  station.  Tliat  used 
at  the  Naval  Experimental  Battery,  Annapolis,  and  deduced 
from  what  are  considered  the  most  reliable  data,  is  g = 32.1533. 


Lxj.  vvxxat  aio  v>uiiOiU.ci cu.  tllc  lllUOL  icilciuiu  uata,  lo  ^ 1.0KJK}* 

1329.  STEAIN  UPON  THE  GUN.— The  resistance  op- 


posed to  the  motion  of  a projectile  in  the  bore  of  a gun,  and 
which  tends  to  increase  the  explosive  force  of  the  powder,  de- 
pends upon  the  form  and  weight  of  the  projectile,  upon  the 
circumstance  of  the  piece  being  smooth-bored  or  rifled,  and 
upon  the  system  of  rifling  adopted. 

The  projectile  will  commence  to  move  when  the  force  of 
the  gas  has  become  equal  to  the  resistance  offered  to  motion. 

The  time  necessary  for  the  conversion  into  gas  of  the 
quantity  of  powder  required  to  move  the  projectile,  will  depend 
upon  the  nature  of  the  gunpowder  used,  the  form  of  the  cart- 
ridge, and  the  point  of  ignition  of  the  latter. 

* EiemenU  of  Natural  Philosophy,  by  Professor  Sir  W.  Thompson  and  P.  G. 
Tait.  Oxford ; 1873. 


y G (1  + .00513  Siffi  A). 


490 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  maximum  strain  upon  the  metal  of  the  gun  will  mainly 
depend  upon  the  rapidity  of  the  conversion  of  the  powder 
into  gas. 

1830.  The  initial  velocity  of  the  projectile  may  not,  how- 
ever, be  in  proportion  to  the  maximum  strain,  hut  it  varies  as 
the  work  done  on  the  projectile,  or  as  the  pressures  into  the 
spaces  through  which  they  act,  or : 


PS= 


where  P= pressure  of  gas, 

S = space  through  which  P acts, 

W^iweight  of  j)rojectile, 

V=: velocity  of  projectile, 
g=r  force  of  gravity. 

And  if  S be  a very  small  interval,  a fair  approximation  to 
the  mean  strain  exerted  through  it  in  the  bore  of  a smooth- 
bored  gun  may  be  calculated  by  this  formula. 

1331.  Pkessuee-gauges. — These  are  instruments  used  for 
determining,  by  the  method  of  indentation^  the  pressure  exerted 
within  the  bore  of  the  gun  by  the  ignition  of  the  powder. 

1332.  PoDMAxr’s  Pkessure-gauge  is  shown  in  Fig.  301, 

and  in  using  it,  a hole  is  drilled 
through  the  gun  at  any  point  or 
points  in  the  bore  whei'e  it  is 
desired  to  ascertain  the  pressure 
exerted  by  the  exploding  charge. 
Into  this  hole  the  tube,  A,  is 
screwed,  its  lower  end,  which  is 
open,  being  flush  with  the  bore. 

The  other  end  is  closed  with 
the  piston,  or  indenting-tool,  B, 
the  joint  being  rendered  tight 
by  means  of  the  gas-check,  g. 
The  piston  carries  a knife,  13. 
(Art.  424),  and  upon  the  knife 
rests  a piece  of  copper,  E,  which 
is  held  tightly  against  it  by  the 
screw,  S. 

The  hole  in  the  tube  shown 
at  C,  and  the  recess  around  the 
stem  of  the  indenting-tool,  are 
made  for  the  purpose  of  letting 
the  piston,  and  thus  prevent  its 


Fig.  301. — Capt.  Rodman’s 
pressiu-e  piston.  (Section.) 


out 


any  gas  that  might 
acting  against  the  shoulder  of 


pass 


the  indenting-tool. 


INSPECTION  OF  GUNPOWDER. 


491 


B 


1333.  Use. — In  nsing  this  apparatus  the  shank  or  piston  of 
the  indenting-tool  and  the  hole  in  the  tube  into  whicdi  it  is  in- 
serted for  use  are  well  cleaned  and  oiled,  and  the  indenting-tool 
inserted  into  the  tube,  which  is  then  screwed  into  the  gun,  and 
a disk  of  soft  copper  placed  on  the  point  of  the  indenting-tool, 
the  disk  being  held  in  position  by  the  screw,  S,  acting  either 
upon  a second  copper  disk  or  upon  a piece  of  iron  having  a 
plain  surface  next  the  disk  to  be  indented. 

The  pressure  on  the  inner  end  of  the  indenting-piston  forces 
the  point  of  the  indenting-tool  into  the  copper  disk  when  tlie 
gun  is  fired. 

This  disk  is  then  removed  to  the  testing-machine,  and 
the  pressure  required  to  produce  an 

equal  indentation  with  the  same  tool.  / [jl  ilif]  \ 
in  the  same  disk,  or  one  from  the 
same  bar  of  copper,  is  accurately 
weighed;  then,  knowing  the  area 
of  a cross-section  of  the  indenting-pis- 
ton, the  pressure  per  square  inch  is 
calculated.  For  the  purpose  of  get- 
ting greater  accuracy  of  results  the 
indenting-point  is  veiy  broad  and 
thin  so  as  to  make  a very  long  cut 
as  compared  with  its  breadth  and 
depth. 

1334.  Ikteknal  Pressure-gauge. 

— This  apparatus  is  placed  wholly 
within  the  bore  of  the  gun,  being 
inserted  in  the  bottom  of  the  car- 
tridge-bag, and  having  the  charge 
filled  in  over  it  so  that  no  powder 
will  get  under  it  and  come  between 
it  and  the  bottom  of  the  bore  when 
rammed  home  in  the  gun. 

Fig.  302  shows  the  construction 
of  this  instrument. 

A,  outer  cylinder;  B,  screw-plug 
for  closing  mouth  of  outer  cylinder ; 

G,  copper  gasket  to  form  gas-tight 
joint ; C,  specimen  of  copper  to  be 
indented  ; I,  indenting-tool ; P,  in- 
denting piston ; y,  gas-check. 

1335.  Use. — All  its  parts  except  the  exterior  of  the  outer 
cylinder  are  carefully  cleaned  before  each  fire,  and  the  threads 
of  the  screw-plug  and  the  indenting-piston  carefully  oiled ; the 


492 


NAVAL  ORDNANCE  AITO  GUNNERY. 


copper  specimen  is  then  placed  in  the  bottom  of  the  cylinder, 
the  indenting-piston  inserted  into  the  screw-plug,  and  with  the 
outer  cylinder  horizontal,  the  plug  is  screwed  home ; being 
afterwards  tightly  set  in  with  a wrench  while  the  cylinder  is 
held  in  a vice.  The  cylinder  is  then  carefully  set  down  upon 
the  closed  end,  and  the  indenting-piston  gently  pushed  down 
till  the  point  of  the  indenting-tool  rests  upon  the  copper  speci- 
men ; a small  gas-check  is  then  inserted,  mouth  outwards,  till  it 
rests  upon  the  end  of  the  indenting-piston. 

1336.  At  the  Naval  Experimental  Battery,  a gauge  called 
the  “ double  ping,”  from  its  giving  two  indications,  has  been 
designed  for  use  with  disks  of  pure  silver,  and  the  records  of 
pressure  obtained  are  very  reliable. 

The  instrument  is  inserted  into  the  gun  with  the  screw-plug 
towards  the  muzzle,  and  is  generally  found  in  the  bore  of  the 
gun  or  near  the  piece  after  its  discharge,  when  the  screw- 
plug  is  withdrawn,  and  the  specimen  removed,  having  an  in- 
dentation in  its  surface,  due  to  the  pressure  that  has  been 
exerted  upon  the  outer  end  of  the  indenting-piston. 

1337.  The  indications  of  pressure  by  thus  instrument  are 
generally  found  to  be  something  less,  for  equal  charges  of 
powder,  than  those  by  the  external  gauge. 

One  reason  for  this  is  probably  owing  to  the  fact  that  in  the 
external  gauge  the  gas  has  a considerable  space  to  travel 
through  between  the  powder-chamber  and  the  indicating  parts, 
so  that  before  reaching  the  piston  the  gases  have  attained  a 
high  vis-viva,  especially  with  quick-burning  powders. 

To  enable  those  who  have  not  the  means  of  detennining 
the  pressure  corresponding  to  a given  length  of  indentation  to 
obtain  approximate  results  from  the  pressure-gauge,  tables  are 
constnicted  by  accurately  measuring  the  length  of  cut  due  to 
each  100  lbs.  of  pressure. 

1338.  Makvin’s  Estimator  * is  an  instrument  for  measur- 
ing and  verifying  indentations  in  the  disks  used  with  the  pres- 
sure-gauge. 

Description. — Fig.  303  is  a profile,  and  Fig.  304  a midship 
vertical  section  of  the  Estimator.  The  instrument  consists 
(Fig.  304)  of  a cutter-stein,  ABC,  cylindrical  as  far  as  B, 
and  from  B to  C rectangular,  as  per  cross-section.  This 
stem  carries  two  nuts,  E and  F,  and  one  disk,  D ; E,  working 
on  a left-handed  screw  of  12  the  inch  pitch  • F,  on  a right- 
handed  thread  cut  accurately  to  inch  pitch. 

The  lower  end  of  the  cutter-stem  is  grooved  to  receive  the 


Designed  by  Comdr.  J.  D.  Marvin,  U.  S.  Navy. 


INSPECTION  OP  GCJNPOWDER. 


493 


feather  of  a knife,  m,  about  1 inches  long.  G is  cylindrical 
from  a to  5,  hut  square  from  h to  c,  and  has  through  it  a 
slot  in  which  the  lower  end  of  the  cutter-stem,  ABC,  fits  accu- 
rately. H is  a square  plate  having  in  its  centre  a circular 
recess  to  contain  the  disk,  I.  J is  the  saucer  which  centres 
the  plate,  H,  and  guide-block,  G]  e e (Fig.  304)  are  holes  in 
which  to  place  a punch,  to  drive  out  the  disk  or  plate  in  case 
they  jam.  K (Fig.  303)  is  a pointer  with  a bob  on  its  end, 
pivoted  at  d,  in  a slot  cut  in  G ; it  is  horizontal  when  the  nut, 
F,  rests  on  G,  but  drops  down  by  its  own  weight  when  they 
are  separated. 

The  nut,  F,  is  of  precisely  3.183  inches  diameter  on  the  out- 


Cross  section  on  x y. 


Fig.  304. 

side,  the  circumference  being  10  inches;  this  has  a scale  of 
inches  marked  upon  it,  and  is  graduated  to  .02  inches.  The 
cutter  has  a trifle  over  0.2  inch  vertical  play,  which  exceeds  the 
depth  of  an  ordinary  cut. 

When  the  point  of  the  cutter  is  tangent  to  the  disk,  I,  the 
zero  of  the  scale  on  F should  be  opposite  the  point  L ; F 
resting  firmly  on  G,  and  the  pointer,  K,  horizontal. 


494 


NAVAL  OKDNANCE  AND  GTINNEET. 


The  length  of  cut  coiTesponding  to  any  given  projection  of 
the  cutter  beyond  the  lower  face  of  G may  be  determined 
either  mathematically  or  by  experiment. 

The  pitch  of  the  screw  on  which  F works  being  inch, 
and  the  diameter  of  F being  3.183  inches  graduated  to  liftieths 
of  an  inch  on  the  circumference,  it  follows  that  the  extension 
of  the  cutter  can  be  read  by  the  index,  L,  to  ^ ^ ^ of  an  inch. 
By  applying  inside  calipers  between  D and  F at  f and  y,  a 
check  can  always  be  had  on  the  setting  of  the  cutter. 

1339.  Use. — Place  the  disk  in  the  recess  of  the  plate,  H, 
and  place  H in  the  saucer,  J.  Adjust  the  guide-block,  G,  on 
the  top  of  H,  slack  up  the  locking-nut,  E,  and  revolve  F the 
number  of  times  necessary  to  give  the  play  between  F and  G 
needed  to  make  the  required  cut.  Bun  down  the  locking-nut 
firmly,  to  relieve  the  thread  of  F of  as  much  strain  as  possible. 
Insert  the  cutter-stem  in  the  slot,  G,  and  the  instrument  will 
now  be  ready  to  place  in  the  testing-machine,  where  weights 
are  applied,  until  the  pointer,  K,  comes  horizontal  as  shown  by 
a mark  on  the  index,  L.  As  soon  as  the  pointer  is  up,  reverse 
the  crank  and  relieve  the  pressure.  The  pressure  comes  upon 
the  point  indicated  by  the  arrow. 

A graduated  scale  of  lengths  of  cut  corresponding  to  readings 
on  the  circular  scale  F,  is  used  with  the  estimator.  The  reading 
corresponding  to  the  length  of  the  cut  to  be  duplicated  is  brought 
opposite  to  the  point  L.  The  cutter  actually  used  in  the  pres- 
sure gauge,  is  used  in  the  estimator,  on  a fresh  uncut  disk. 
The  power  required  to  force  the  knife  down  to  duplicate  the 
cut  is  the  measure  of  the  pressure. 

1340.  The  Ckusuer-gauge. — This  is  a term  applied  to  the 
English  pressure-gauge.  (Fig.  305.)  It  consists  of  a tube  or 
cylinder  of  steel  wdnch  admits  of  the  insertion  of  a small 
cylinder  of  copper,  B,  which  is  retained  in  the  centre  of  the 
chamber,  c d e by  a small  w'atch-spring.  One  end  of  this 
cylinder  rests  against  an  anvil.  A,  and  the  other  is  acted 
upon  by  a movable  piston,  C,  which  is  kept  tight  against 
the  cylinder  by  the  spring,  i.  A gas-check,  D,  is  inserted 
against  the  lower  extremity  of  the  piston,  and  should  any  gas 
get  past  this,  there  are  passages  by  which  it  can  escape  into  the 
open  air.  In  this  apparatus  the  method  of  compression  is  used 
for  ascertaining  the  pressures. 

The  crusher-gauge  is  used  in  exactly  the  same  way  as  the 
Kodman-gauge.  "Upon  the  explosion  of  the  charge  the  gas 
acts  upon  the  area  of  the  piston  and  crushes  the  copper  cylin- 
der against  the  anvil.  The  amount  of  compression  the  copper 
thus  sustains  becomes  an  indication  of  the  pressm-e  exerted 
upon  the  piston. 


INSPECTION  OF  GENPOWDEE. 


495 


.1341.  In  order  to  obtain  data  whereon  to  base  tbe  calcula- 
tions of  tbe  pressures,  a series  of  experiments  is  made  by  means 
of  a testing-instrument  to  determine  the  pressure  required  to 
produce  a definite  amount  of  compres- 
sion on  copper  cylinders  similar  to  those 
used  in  the  instrument.  The  results  of 
these  experiments  are  tabulated,  and 
they  furnish  a means  of  comparison 
whereby  the  amount  of  compression 
produced  in  the  crusher  becomes  a 
direct  indication  of  the  pressure  exerted 
by  the  gases  at  that  part  of  the  bore 
where  the  gauge  is  placed. 

1342.  The  results  of  experiments 
show  that  the  copper  disks  cannot  be 
depended  upon  to  give  uniform  re- 
sults, but  latterly  disks  of  pure  silver 
have  been  employed,  and  the  margin  of 
error  has  been  much  reduced. 

1343.  One  great  obstacle  to  the 
attainment  of  correct  pressui’e  indica- 
tions is  the  ditficulty  of  obtaining  per- 
fect uniformity  in  the  quality  of  the 
metal  upon  which  the  pressures  are  re- 
corded. To  this  possible  defect  as  well 
as  the  probable  imperfect  action  of  the 
piston  may  be  attributed  the  very  wide 
differences  between  the  results  some- 
times obtained  with  equal  charges  of 
the  same  kind  of  powder. 

1344.  Pkessuke-cukves. — Having 
obtained  the  pressures  and  velocities 


pressures 

as  they  actually  occur  in  the  bore,  we 
may  make  a graphic  representation  of 
them  by  constructing  a curve  which 
would  have  for  abscissas  the  times,  and 
for  ordinates  the  pressures,  of  the  gases. 

We  would  find  it  somewhat  similar  to 
Fig.  306.  That  is,  the  tension  increases 
with  great  rapidity  in  the  first  moments 
of  combustion ; it  attains  promptly  the 
maximum,  and  then  decreases  with  less  rapidity.  It  is  to  this 
circumstance  that  are  due  the  bursting  properties  of  the  powder 
and  the  destructive  effects  which  it  sometimes  exerts  upon  the 
bore  of  the  piece. 


Fig.  305. — ^Sectional 
elevation  of  Crashing-in- 
strument. 


496 


NAVAL  OEDNANCE  AND  GUNNERY. 


But  with  equality  of  charge  the  curve  is  found  to  vary  very 
much  with  difEerent  powders  ; therefore  it  is  desirable  to  pro- 
duce such  a powder  that  the  curve  O M B may  he  replaced  by 
a curve  such  as  O M'  B',  in  which  the  maximum  may  he  less 
elevated,  but  whose  total  area  may  be  equal  or  even  superior. 

Thus  we  should 
endeavor  to  take 
away  from  the  pow- 
der its  bursting  pro- 
perties and  preserve 
to  the  projectile  the 
same  velocity  in 
leaving  the  bore,  or 
even  impress  upon 
it  a greater  velocity. 
In  order  to  accom- 
plish this  it  is  neees- 
, sary  to  consider  what 

has  been  said  under 
-X  the  head  of  Exjplo- 

Fig.  306.  si'-oQ  Force  of  Gun- 

2)owder  1198). 

1345.  IIYGEOMETBIC  QUALITIES. -If  the  powder 
be  made  of  pure  materials  and  have  the  required  density,  its 
hygroinetric  quality  follows  as  a matter  of  course.  It  may  be 
determined  by  exposing  the  powder  to  air  saturated  with  moist- 
ure. For  this  purpose,  samples  of  about  1,500  grains  weight 
may  be  placed  in  a shallow  tin  pan,  nine  inches  by  six  inches, 
set  in  a tub  the  bottom  of  which  is  covered  with  water.  The 
pan  of  powder  should  be  placed  about  one  inch  above  the  sur- 
face of  the  water,  and  the  tub  covered  over.  In  this  manner 
any  sample  of  powder  may  be  compared  with  another  of  known 
good  quality.  Good  powder,  made  of  pure  materials,  will  not 
absorb  more  than  two  and  a half  per  cent,  of  moisture  in  twenty- 
four  hours. 

1316.  ANALYSIS. — Whatever  may  be  the  mode  of  proof 
adopted,  it  is  essential,  in  judging  of  the  qualities  of  gunpow- 
der, to  know  the  mode  of  fabrication,  and  the  proportions  and 
degree  of  purity  of  the  ingredients.  The  latter  point  may  be 
ascertained  by  analysis. 

The  following  plan  is  recommended  by  Fresenius  : 

Determination  of  the  Moisture. — A\teigh  two  or  three 
grams  of  the  substance  (not  reduced  to  dust  or  pulverized) 
between  two  well-litting  watch-crystals,  and  dry  in  the  desic- 
cator, over  concentrated  sulphuric  acid,  or  at  a gentle  heat. 


INSPECTION'  OF  GEIs^POWDEE. 


497 


not  exceeding  69°  centigrade,  till  tlie  weight  remains  con- 
stant. 

Deter mmation  of  the  Saltpetre. — Place  an  accurately 
v/eighed  quantity  (about  live  grams)  on  a lilter  and  moisten 
with  water;  then  saturate  w'th  water,  and  after  some  time, 
repeatedly  pour  small  quantities  of  hot  water  upon  it,  until 
the  nitrate  of  potassium  is  completely  extracted.  Eeceive 
the  first  filtrate  in  a small  weighed  platinum  dish,  and  the 
washings  in  a beaker.  Evaporate  the  contents  of  the  platinum 
dish  cautiously,  adding  the  Avashings  from  time  to  time ; 
heat  the  residue  cautiously  to  incipient  fusion,  and  Aveigh 
it. 

Determination  of  the  Sulphur. — Oxydize  tAvo  or  three 
grams  of  the  powder  with  pure  concentrated  nitric  acid  and 
c'llorate  of  potassium,  the  latter  being  added  in  small  portions, 
Avhile  the  fluid  is  maintained  in  gentle  ebullition.  If  the  opera- 
tion is  continued  long  enough,  it  usually  happens  that  both  the 
charcoal  and  sulphur  are  fully  oxydized,  and  a clear  solution  is 
finally  obtained.  Evaporate  with  excess  of  pure  hydro  chloric 
acid  in  a water-bath  to  dryness;  filter,  if  undissolved  charcoal 
should  render  it  necessary,  and  then  precipitate  the  sulphuric 
acid  by  barium  chloride  with  the  usual  precautions. 

Determination  of  the  Charcoal. — Digest  a weighed  portion 
of  the  powder  repeatedly  with  sulphide  of  ammonium,  till  all 
the  sulphur  is  dissolved  ; collect  the  charcoal  on  a filter  (previ- 
ously dried  at  100°  and  Aveighed),  wash  it  first  Avith  Avater  con- 
taining sulphide  of  ammonium,  then  with  pure  Avater ; dry  at 
100°  and  Aveigh. 

The  charcoal  so  obtained  must,  under  all  circumstances,  be 
tested  for  sulphur  by  the  method  glA'en  above,  and,  if  occasion 
require,  the  sulphur  must  be  determined  in  an  aliquot  part. 

These  operations  can  only  be  performed  with  accuracy,  in  a 
properly  appointed  chemical  laboratoiy,  by  one  someAvhat  ex- 
perienced in  quantitative  analysis. 

1347.  IXSFECTIOX  DEPORT. — The  report  of  inspection 
should  shoAv  p>lace  and  date  of  fabincation  and  of  proof;  the 
hind  of  powder  and  its  general  equalities,  as  the  number  of  grains 
in  100  grs. ; whether  hard  or  soft,  round  or  angular ; of  uni- 
form or  irregular  size  ; whether  free  from  dust  or  not ; the  ini- 
tial velocities  obtained  in  each  fire  ; the  amount  of  qiressure  for 
each  charge  ; the  amount  of  moisture  absorbed ; and,  finally,  the 
height  of  the  barometer  and  hygrometer  at  the  time  of  the 
proof. 

1348.  Marks  on  the  Barrels. — Barrels  must  be  marked 
on  the  head  (Fig.  307)  with  maker’s  name,  date  of  manufac- 
•32 


498 


NAVAL  ORDNANCE  AND  GUNNERY. 


ture,  initial  velocity  when  manufactured,  density,  pressure, 
kind  of  powder,  lot,  class,  last  initial  velocity  and  pressure  ob- 

1349.  Restokixg  TJnseevice-ujle 
Powder. — When  powder  lias  been 
damaged  by  being  stored  in  damp 
places,  it  loses  its  strength.  If  the 
quantity  of  moisture  absorbed  does  not 
exceed  seven  per  cent.,  it  is  sufficient 
to  dry  it,  to  restore  it  for  service. 
This  is  done  by  exposing  it  to  the 
sun. 

1350.  Condemned  Powder. —"Wlien 
powder  has  absorbed  more  than  seven 
per  cent,  of  water,  it  is  condemned, 

and  sent  to  the  powder-mills  to  be  worked  over. 

When  it  has  been  damaged  with  salt  water  or  become  mixed 
with  foreign  matter  which  cannot  be  separated  by  sifting,  the 
nitre  is  dissolved  out  from  the  other  materials  and  collected  by 
evaporation. 

When  powder  is  condemned  by  survey,  it  should  be  turned 
into  store ; as  the  nitre  contained,  which  forms  three-fourths  of 
the  powder,  is  still  perfectly  good,  and  can  be  made  serviceable 
in  making  new  powder.  (Art.  1066.) 

1351.  Purchasing  Powder  Abroad. — In  case  of  necessity, 
powder  for  saluting  may  be  purchased  abroad  in  order  to  pre- 
serve a supply  of  our  own  proof-powder  for  battle. 

Should  it  become  necessary  to  use  powder  for  service  charges 
which  has  not  been  regularly  inspected  and  proved  in  the  man- 
ner required  by  regulations,  such  tests  of  it  must  be  made  as 
circumstances  will  admit.  The  ranges  given  by  it  may  be  com- 
pared with  those  of  service  powder  of  good  quality  under  the 
same  circumstances.  If  deficient  in  strength,  the  quantity  of 
the  charges  should  be  increased,  until  the  ranges  are  equalized, 
in  order  that  the  sight-bar  may  still  indicate  the  proper  ele\  a- 
tions  for  each  charge  and  distance. 


Fig.  307. 


Section  IV. — Preservation  and  Storage  of  Gunpowder. 

1352.  PEESERYATIOX  AXD  STORAGE.— In  the 
stowage  of  powder,  both  ashore  and  afloat,  especial  pains  should 
be  taken  to  secure  it  from  the  dangers  of  explosion  and  the 
effects  of  moisture ; and  to  this  end  great  care  is  observed  in 
the  construction  and  locality  of  magazines  and  shell-rooms,  par- 


STORAGE  OF  GUNPOWDER. 


499 


ticiilarly  on  board  ship,  where  many  details  have  to  he  consid- 
ered, and  every  possible  precaution  taken  to  accommodate  the 
full  allowance  of  powder  completely,  to  guard  it  to  the  utmost 
against  injury  and  accidental  explosion,  and  to  deliver  it  from 
the  magazine  as  required,  with  facility  and  certainty. 

1353.  Magazines  on  Shore  for  the  storage  of  gunpowder 
are  generally  built  of  brick  or  stone  in  a very  substantial  man- 
ner, and  in  places  free  from  moisture,  and  should  be  remote 
from  danger.  The  magazine  should  be  fire-proof  and  dry,  and 
protected  by  lightning-rods,  which  are  attached  to  masts  or 
poles  planted  from  six  to  ten  feet  from  the  walls  of  the  build- 
ing ; the  mast  should  be  of  such  height  that  the  point  of  the 
stem  may  be  about  fifteen  feet  above  the  building.  Magazines 
should  never  be  opened  while  there  is  thunder  and  lightning. 

For  the  preservation  of  the  powder,  and  of  the  floors  and 
lining  of  the  magazine,  it  is  of  the  greatest  importance  to  pre- 
serve nnobstrueted  the  circulation  of  air  under  the  flooring  as 
well  as  above.  The  windows  should  have  inside  shutters  of 
copper  wire-cloth.  The  ventilators  must  he  kept  free.  JSTo 
shrubbery  or  trees  should  be  allowed  to  grow  so  near  as  to 
protect  the  building  from  the  sun.  The  magazine-yard  should 
be  paved  and  well  drained,  and  kept  scrupulously  clean. 

1354.  Storage. — Powder  barrels  in  magazines  on  shore, 
when  there  are  no  racks,  should  be  stowed  on  their  sides,  with 
their  marked  ends  towards  the  alleys,  three  tiers  high,  or  four 
tiers  if  necessary,  with  small  skids  on  the  floor  and  between  the 
several  tiers  of  barrels,  using  chocks  at  intervals  on  the  lower 
skids  to  prevent  the  barrels  from  rolling.  If  it  is  necessary 
to  pile  the  baiTels  more  than  four  tiers  high,  the  upper  tiers 
should  he  supported  by  a frame  resting  on  the  floor ; or 
the  barrels  may  be  placed  on  their  heads  with  boards  between 
the  tiers. 

Whenever  practicable,  the  barrels  should  be  arranged  in 
double  rows,  with  a passage-way  between  the  rows,  so  that 
the  marks  on  each  barrel  may  be  seen  at  a glance,  and  any 
barrel  easily  reached. 

Barrels  must  be  carefully  examined  before  putting  them 
into  the  magazines,  to  see  that  they  are  perfectly  tight ; that 
the  hoops  are  not  fastened  with  iron  nails  ; that  there  is  no  iron 
or  anything  objectionable  about  the  barrel. 

1355.  The  powder  should  be  separated  - according  to  its 
kind,  the  place  and  date  of  fabrication,  and  the  proof-range. 

Each  parcel  of  powder  should  be  inscribed  on  a ticket  and 
attached  to  the  pile,  showing  the  entries  and  the  issues. 

Powder,  when  stored  in  magazines  on  shore,  must  be 


500 


NAVAL  ORDNANCE  AND  GUNNERY. 


kept  only  in  barrels,  and  arranged  in  lots,  being  cdassed  as 
follows : 

Class  1.  New  powder. 

Class  2.  Powder  returned  from  skips  and  otlier  sources 
wbicb  has  been  found  after  proof  to  be  up  to  the  recpiired 
standard  for  servdee. 

Class  3.  Returned  powder,  fit  only  for  filling  projectiles. 
(Powder  taken  from  projectiles  shall  be  used  again  only  for 
filling  projectiles.) 

Class  4.  Returned  powder  fit  only  for  saluting. 

Class  5.  Powder  unfit  for  use. 

There  should  be  an  unencumbered  space  of  six  or  eight  feet 
square  at  the  door  or  doors  of  the  magazine. 

1356.  Peesekvation. — Powder-houses  or  magazines  on  shore 
are  to  be  inspected  by  the  ordnance  officer  at  least  once  in 
every  week,  and  every  precaution  taken  to  guard  them  against 
explosion,  and  to  preserve  the  powder  dry  and  in  good  condi- 
tion. 

Magazines  should  be  opened  and  aired  in  clear,  dry  weather, 
when  the  temperature  of  the  air  outside  is  lower  than  that 
inside  the  magazine.  The  moisture  of  a magazine  may  be  ab- 
sorbed by  chloride  of  lime  or  charcoal,  suspended  in  an  open 
box  under  the  arch  of  the  door,  and  i-enewed  from  time  to  time. 

The  use  of  quicklime  is  dangerous  and  forbidden. 

The  powder  in  barrels  should  be  turned  from  time  to  time, 
at  least  as  often  as  every  three  months,  and  being  arranged  as 
mentioned  before,  the  oldest  powder  will  always  be  accessible 
for  first  delivery,  without  disturbing  that  of  more  recent  man- 
ufacture. 

1357.  Seevice  of  the  Magazine. — Mhen  powder  is  han- 
dled in  powder-houses  or  magazines  on  shore,  either  for  the 
purpose  of  inspection  or  preparation  for  delivery  to  ships,  the 
baize-cloth  is  to  be  spread,  and  the  people  before  entering  the 
magazine  must  divest  themselves  of  every  metal  implement, 
empty  their  pockets, — that  nothing  likely  to  produce  fire  may 
escape  detection, — and  put  on  the  magazine-dresses  and  slip- 
pers. Neither  loose  powder  nor  open  barrels  will  be  jaermitted 
to  remain  in  a magazine,  nor  shall  barrels  on  any  account  be 
opened  in  a magazine.  Should  a barrel-head  start,  the  barrel 
must  be  immediately  removed  to  the  shif tiny-house,  and  the 
powder  shifted  into  a sennceable  barrel.  The  barrels  must  be 
opened  only  on  the  fiooi’-cloth  in  the  shiftiug-honse,  and  no 
metallic  setter  used  in  driving  either  copper  or  wooden  hoops. 
Powder-barrels  should  never  be  opened  except  when  required 
for  use,  as  grains  of  powder  falling  between  the  staves  would 


STORAGE  OF  GUOTOWDER. 


501 


prevent  tlieir  being  tightened.  Samples  must  always  be  taken 
from  tlie  bungs. 

Magazine-dresses. — They  are  to  be  of  worsted,  like  a simple 
shirt,  to  reach  to  the  knees ; no  metal  buttons  to  be  worn. 

Magazine-slippers. — They  must  be  made  wholly  of  cotton, 
cloth  or  buckskin.  In  hot  or  warm  climates  the  naked  feet  are 
generally  preferred.  India-rubber  and  woolen-slippers  are  pro- 
hibited. 

1358.  Fixed  Ammunition  should  not  be  put  in  the  same 
magazine  with  powder  in  barrels. 

Fireworks  should  never  be  stored  in  a powder-maga- 
zine. 

1359.  llhe  2Lagazine  Ledger  should  show  at  all  times  the 
quantity  of  powder  on  hand,  the  number  of  barrels,  the  marks 
on  each  barrel,  and,  in  fact,  a complete  history  of  ail  the  pow- 
der in  the  inai>;azine. 

1360.  Issuing  Poioder. — When  powder  is  to  be  issued  for 
use  to  any  vessel,  it  shall  be  selected  as  far  as  practicable  from 
dehveries  made  by  the  same  manufacturer,  at  the  same  time  or 
date.  The  powder  is  measiued  in  copper  measures  and  put 
into  cartridge-bags,  and  the  cartridges  stowed  in  powder-tanks. 
A correct  history  of  all  powder  issued  must  accompany  it. 
When  powder  is  shifted  from  one  barrel  or  tank  to  another, 
care  must  be  taken  to  remove  all  old  marks,  and  to  mark  the 
barrel  correctly  for  its  contents. 

Great  irresrularities  bavin<;  been  discovered  in  the  weijrht  of 
cartridges  supplied  from  the  difterent  magazines,  it  is  ordered 
that  at  least  teir  measures  shall  be  weighed  at  each  filling,  and 
allowance  made  for  different  densities,  by  using  a small  com- 
pensating measure  to  supply  the  deticieney  or  to  remove  the 
excess. 

1361.  Ships’  MAGAzixrES.— All  powder,  wliether  public  or 
private,  must  be  safely  stowed  in  the  magazine. 

Form. — In  view  of  the  fact  that  all  the  powder  for  use  on 
board  of  ships  is  now  put  up  in  carti idge-bags  and  stowed  in 
cubical  copper  tanks  made  water-tight,  the  form  of  magazines 
sliould  be  as  nearly  rectangidar  as  the  shape  of  the  vessel  will 
admit. 

Strength. — They  should  be  built  strong  enough  to  resist 
sufficiently  the  effect  of  the  working  of  the  vessel  in  heavy 
weather,  and  also  the  pressure  of  water  they  will  have  to  sustain 
in  case  of  being  flooded. 

Situation. — When  there  is  only  one  magazine,  it  is  always 
in  the  after  part  of  the  vessel;  but  when  two,  one  aft,  the 
other  forward ; and  they  are  to  be  as  nearly  equal  iu  regard 


602 


NAVAL  ORDNANCE  AND  GUNNERY. 


to  capacity  as  the  shape  of  the  vessel  and  other  ch’cumstances 
will  admit. 

13G2.  Construction. — The  magazine  con.sists  of  three  parts: 
(Fig.  308.) 

The  room  where  the  charges  are  stowed ; a small  delivery- 


Lil 


Fig.  308. 

room  or  passage,  nsnally  athwartship,  immediately  outside  of 
this,  into  which  the  charges  are  passed  before  going  on  deck  ; 
and  the  light-rooms,  or  boxes. 

The  magazine  and  its  passage,  considered  as  one,  must  he 
made  perfectly  water-tight,  by  caulking  the  bottom  and  sides, 
and  then  lining  them  internally,  first  with  white-pine  boards, 
tongued  and  grooved,  and  again  with  sheets  of  lead  of  extra 
thickness,  soldered  together  over  these  boards.  Both  these  lin- 
ings are  to  extend  entirely  over  the  bottom,  or  floor,  and  all  the 
way  up  to  the  crown  on  all  sides. 

When  the  magazine  reaches  the  ceiling  of  the  ship  it  must 
he  battened  oft'  two  inches ; the  lining  of  the  floor  must  be 
battened  up  one  inch,  and  also  the  magazine-deck,  so  that  water 
leaking  through  the  sides  of  the  vessel  may  run  by  and  under, 
and  not  into,  the  magazine. 

An  external  lining  of  sheet-iron  must  he  resorted  to  as  a 
pi’otection  against  Are,  and  to  prevent  the  intrusion  of  rats. 

When  it  is  impossible  to  avoid  extending  the  sides  of  the 


STOEAGE  OF  GUNPOWDER. 


503 


magazine  so  far  out  towards  tlie  skin  of  the  ship  as  to  leave 
only  an  air-passage  on  either  side,  the  crown  should  be  at  least 
six  feet  below  the  deep  load-line. 

In  all  cases  where  this  crown  is  less  than  six  feet  below  that 
line,  the  sides  should  he  made  susceptible  of  protection  by 
allowing  a space  to  interpose  materials,  such  as  sand,  coal,  or 
water  in  tanks,  between  them  and  the  interior  planking  of  the 
ship.  An  average  space  of  six  feet  or  more  on  both  sides  will 
be  sufficient. 

Under  no  circumstances,  however  Avell  the  side  be  guarded, 
should  the  crown  of  the  magazine,  if  it  can  he  avoided,  he  less 
than  four  feet  below  the  load-line. 

Their  floors  may  rest  on  the  kelson,  hut  should  not  come 
below  it. 

1363.  Their  height  should  he  equal  only  to  an  exact  num- 
ber of  times  the  height  of  a powder-tank  when  lying  on  its 
side,  in  addition  to  the  thickness  of  the  shelving ; an  additional 
inch  should  he  allowed  for  play  or  spring. 

The  whole  height  in  the  clear  should  be  limited  by  the  con- 
dition that  a inan  standing  on  the  floor  may  reach  the  upper 
tier  of  tanks  with  ease. 

Four  tiers  of  200-pound  tanks,  three  of  them  resting  on 
shelves  two  inches  thick,  and  the  other  on  inch-battens  on  the 
magazine-floor,  with  an  allowance  of  one  and  a half  inch  for 
play,  will  require  a height,  in  the  clear,  of  six  feet  two  Inches. 
Both  safety  and  convenience  would  suggest  this  as  the  maxi- 
mum limit  m height,  even  for  the  largest  magazine. 

If,  however,  in  a ship  of  great  draft  of  water,  it  should  he 
found  practicable  to  have  height  enough  for  live  tiers  of  tanks, 
then  the  lower  tier  may  he  laid  so  as  to  occupy  the  whole  of 
the  magazine-floor ; and  on  the  top  of  this  tier,  in  the  alley- 
way,  a light  false  bottom  is  to  be  placed  for  the  men  to  stand 
upon  to  enable  tliem  to  reach  the  upper  tier,  which  is  the  one 
that  should  he  exhausted  flrst.  Thisialse  bottom  should  be 
made  of  gratings,  and  in  sections  convenient  for  speedy 
removal.  ' 

A magazine  aft  in  a ship  is  to  have  its  passage  for  deliver- 
ing powder  adjoining  its  forward  part ; and  one  forward  in  a 
ship  is  to  have  this  passage  adjoining  its  after  part,  in  order 
that  it  may  never  be  necessary  to  pass  powder  over  the  light- 
box scuttle. 

1361.  As  many  doors,  D (Fig.  309),  are  to  be  cut  in  the 
hulk-head,  I II  (Fig.  308),  separating  this  passage  from  the 
magazine-room,  as  there  are  alle_ys  to  be  left  in  the  latter,  be- 
tween the  racks  or  shelves  on  which  the  tanks  are  stowed ; and 


504 


NAVAL  ORDNANCE  AND  GUNNERY. 


these  doors  must  correspond  -with  those  alleys.  They  are  not 
only  to  afford  a means  of  entrance  to  the  magazines,  but  also 
for  passing  the  tanks  in  and  out. 


Section  on  H I,  Fig.  308. 


Fig.  309. 


Through  the  upper  part  of  each  door  a small  scuttle,  S,  is 
to  be  cut,— two,  if  necessary, — for  the  purpose  of  passing  the 
cartridges  out  of  the  magazine-room  with  the  door  itself  closed ; 
and  is  to  have  a lid  so  arranged  as  to  open  outwards  only,  and 
to  close  of  itself  when  the  scuttle  is  not  actually  in  use. 

Frigates  should  have  two  alleys  for  each  magazine.  In  screw- 
vessels  of  large  size,  where  the  shaft  will  interfere  with  this  ar- 
rangement, two  alleys  for  the  forward  magazine.  In  smaller 
vessels  one  alley  will  suffice.  In  all  cases  the  alley  is  not  to  be 
less  than  two  feet  and  ten  inches  in  breadth,  and  it  ought  to  be 
more,  if  practicable,  to  prevent  confusion  and  delay.  Each 
alley  (A  E,  Fig.  308)  is  to  be  illuminated  by  a separate  light. 

If  there  be  room  in  the  magazine,  there  should  be  space  left 
at  one  end  for  a man  to  pass  from  one  alley  to  the  other  with- 
out going  into  the  passage. 

All  the  metallic  fixtures  about  a magazine,  delivering- 
passage,  and  light-room  mnst  be  of  copper. 

In  order  to  increase  secnrity  against  the  effects  of  lightning, 
a magazine  should  be  placed,  if  jaracticable,  so  as  not  to  include 
a part  of  a mast. 

1305.  Flooding  the  Magazine. — Each  magazine  as  a whole, 
that  is,  including  the  delivery-passage,  being  made  as  stated  be- 
fore, water-tight,  is  to  be  provided  with  an  independent  cock,  T, 
for  filling  it  rapidly  with  water;  a waste-pijie  leading  from  the 
upper  tier  of  tanks  to  carry  off  the  snpei'fiuoiis  water,  and  a 
cock  just  at  the  floor  to  empty  the  magazines  after  having  been 
flooded.  Both  the  cocks  must  be  turned  from  the  decks  above, 
each  having  a lever  attached  to  its  spindle  for  the  ])iir])ose,  dis-. 
tinctl}'^  marked  with  engraved  letters  what  it  is  and  how  it  is 
to  be  used,  and  kept  secured  by  a proper  lock,  the  key  of  which 
is  to  be  kept  among  those  of  the  magazine.  A perforated  disk 
or  strainer  is  to  be  secured  inside  of  the  hole,  at  the  upper  part 


STORAGE  OF  GTJXPOWDER. 


605 


of  tlie  magaziue,  for  tlie  -waste-pipe ; tlie  deli  very -pipes  are 
trapped  to  prevent  vermin  or  vapor  entering. 


Section  on  A-E,  Fig.  308. 


Fig.  310. 


1366.  Lighting  tge  Magazine. — The  magazine  is  to  be 
lighted  by  means  of  one  regulation  lantern,  to  correspond  with 
each  alley  of  the  magazine-room,  placed  in  a box  arranged  for 
the  purpose,  E (Fig.  310). 

The  lantern,  is  fitted  to  hold  a regulation  candle  of  large 
diameter.  The  box,  of  which  a portion  of  the  magazine  bulk- 
head forms  a part,  is  lined  internally  with  soldered  sheets  of 
copper.  The  entrance  to  it  is  at  the  top,  through  a scuttle  in 
the  deck  large  enough  to  admit  the  lantern.  For  single-decked 
vessels  this  scuttle  may  be  surrounded  by  a composition  cover- 
ing pierced  with  holes  one-fourth  of  an  inch  in  diameter,  on  the 
forward  and  after  sides,  near  the  top.  The  cover  must  be  so 
arranged  that,  when  placed  on  in  one  position,  all  the  holes 
will  be  closed ; by  turning  it  half  round,  they  are  all  open,  thus 
supplying  air  to  the  lantern  and  carrying  off  the  smoke.  A 
small  dome  or  reversed  funnel  of  copper,  when  it  can  be  con- 
veniently done,  is  to  be  placed  above  the  lantern  and  fitted 
with  a pipe  of  the  same  metal  to  convey  the  smoke  off.  This 
pipe  may  pass  up  through  the  covering  of  the  light-box,  which  is 
to  have  a plug-hole  lined  with  brass  for  the  purpose,  and  then 
led  farther,  if  necessary,  taking  care,  however,  to  consult  perfect 
safety  throughout. 

The  admission  of  air  to  the  light-box  may  be  from  the  divi- 
sion of  the  hold  in  which  it  is  placed,  by  small  holes  near  its  top, 
through  its  side  or  bacly  protected  with  copper-wire  gauze,  in- 
side and  outside  of  the  box. 

In  the  portion  of  the  magazine  bulkhead  before  alluded  to, 
and  so  as  to  throw  as  much  light  as  possible  into  the  magazine- 
room,  an  opening  with  great  bevelling  is  cut,  which  is  covered 
by  two  plain  glasses  of  suitable  thickness,  somewhat  separated 
from  each  other,  one  of  wFieh,  W (Fig.  311),  that  next  to  the 


506 


NAVAL  ORDNANCE  AND  GUNXERY. 


lantern,  must  be  permanently  fixed ; and  the  other,  that  next 
to  the  magazine,  X,  is  to  be  let  into  a wooden  frame  so  that 
it  may  be  easily  removed,  and  thus  both  glasses  cleaned  with 
convenience  and  safety.  These  glasses  are  held  in  place  by 
brass  screws,  after  being  closely  fitted,  having  their  edges  made 
perfectly  tight. 

1367.  Stowing  the  Magazine. — Ledges  on  the  shelves, 


Section  on  F L,  Fig.  303. 


or  a bar  of  wood  (Fig.  310),  to  ship  and  imshij)  with  facility, 
will  be  provided  for  each  tier  of  tanks  on  both  sides  of  the 
alleys,  to  secure  them  from  getting  out  of  place  when  the  ship 
rolls. 

The  powder-tanks  containing  charges  for  each  class  of  guns 
are  stored  on  their  sides  with  the  lids  next  to  the  alleys  and 
hinges  down,  near  the  magazine-scuttles  through  which  these 
charges  are  delivered.  When  tanks  are  emptied  they  are 
stowed  on  the  upper  shelves  in  order  that  the  powder  may  be 
kept  as  much  as  possible  below  the  water-line. 

Before  the  tanks  are  filled  they  must  be  thoroughly  cleaned, 
and  before  stowing  them  in  the  magazine  the  exteriors  are  care- 
full}'  cleaned  and  the  Kds  examined. 

1368.  Powder  T^vxks. — The  powder-tanks,  for  the  recep- 
tion, and  safe  storage  of  the  powder  on  board  ship,  are  rectan- 
gular metallic  cases,  the  sides  and  bottom  being  of  sheet-copper, 
zinc-coated,  and  the  top  of  composition.  They  have  a circular 
hole  or  opening  in  the  top,  which  is  closed  by  a composition 
lid  on  hinges,  c (Fig.  31i),  and  made  water-tight  by  means  of  a 
rubber-gasket  inserted  in  an  annular  groove  on  the  lower  side 
of  the  lid,  shutting  down  upon  a knife-edge  around  the  opening, 
and  when  closed  is  retained  in  place  by  a screw-bolt  fitted  in 
the  lid  opposite  the  hinges.  There  is  also  a circular  copper  disk, 
or  cover.  A,  fitting  over  the  charges,  inside  the  composition  lid. 
On  the  same  end  are  two  handles  for  transporting  the  tank. 

All  tanks  before  issue  should  be  thoroughly  tested,  to  see 


STORx\GE  OF  GUNPOWDER.  507 

that  they  are  water-tight.  This  is  done  by  immersing  them  in 
water  six  feet  in 
depth,  for  twenty-four 
hours. 

They  are  made  of 
four  sizes  and  are  de- 
nominated as  200  lb., 

150  lb.,  100  lb.,  and 
50  lb.  tanks  respec- 
tively, this  being  their 
capacity  for  powder  in 
grain ; but  the  200- 
pound  tank  is  consid- 
ered the  standard  size 
for  service,  the  others 
being  used  only  in 
exceptional  cases,  and 
to  nil  up  small  vacant 
spaces. 

1369.  The  System 
OF  Marking  Powdee- 
TANKs  is  as  follows : 

The  lid  end  is  painted 
wlhte,  and  is  marked 
with  the  weight  of  Fig,  313, 

cartridge,  number  of 

cartridges,  and  calibre  of  gun  for  which  they  are  intended, 
thus : the  lower  part  of  the  lid  end,  as  the  tank  lies  in  the  rack 
(Art.  1367),  is  marked  with  the  number  of  charges  contained 
(Fig.  313).  Tlie  upper  right-hand  corner  is  marked  with  the 
number  of  pounds  in  each  charge.  The  upper  left-hand  cor- 
ner of  tanks  for  supplying  the  battery,  is  marked  with  the 
calibre  of  the  gun  for  which  the  contents  is  intended,  and  the 
calibre  is  also  marked  in  red  on  the  lid,  in  large  Roman  num- 
erals, for  all  smooth-bore  guns. 

They  are  marked  on  their  upper  sides,  next  the  lid  end,  with 
the  name  of  the  manufacturer,  kind  of  powder,  initial  velocity, 
density,  pressure,  and  date  of  manufacture. 

And  in  order  to  distinguish  more  readily  those  tanks  con- 
taining “Service,”  “Saluting,”  “Torpedo,”  or  other  charges 
from  each  other,  the  following  plan  of  painting  the  lids  has  been 
adopted:  Tanks  containing  sal  uting-charges  have  one-half  of  the 
lid  painted  red,  and  “ Saluting  ” is  marked  on  the  other  half. 

Tanks  containing  shell-charges  have  a red  circle  painted  on 
the  lid,  and  inside  the  circle  is  marked  “ Shell.” 


508 


NAVAL  ORDNANCE  AND  GUNNERY. 


Tanks  containing  powder  for  torpedoes  ai’e  marked  on  tlie 
upper  left-hand  corner  of  tlie  lid  end  “ Toi'pedo,”  and  on  the 


lid  is  marked  in  red  a large  letter  T.  Powder  for  torpedoes  is 
put  in  cartridge-bags  properly  stencilled. 

Tanks  containing  howitzer  charges  are  marked  on  tlie 
upper  left-hand  corner  of  the  lid  end  Howitzer,”  and  on  tke 
lid  is  painted  in  red  a large  letter  II. 

Tanks  containing  sliell-poicder  have  a large  letter  S painted 
in  red  on  the  lid.  This  kind  of  powder  is  put  up  in  any  cou- 
veitient  size  of  bag  which  will  make  the  best  storage,  the  bags 
being  properly  stencilled. 

Tanks  containing  ride-charges,  beside  having  the  calibre 
marked  on  the  upper  left-hand  corner  of  the  lid  end,  have  also 
on  the  lid  a large  letter  P painted  in  red. 

A history  of  the  powder  contained  in  each  is  to  be  pasted 
or  stencilled  on  the  inside  of  the  tank-lid. 

Ho  loose  powder  is  ever  to  be  taken  or  carried  on  board 
ship. 


STOKAGE  OF  GUNPOWDER. 


509 


1370.  Seetice  of  the  Magazine. — Whenever  the  maga- 
zinos  are  opened,  every  precantioii  is  to  be  taken  to  guard 
against  accident  by  fire  ; to  examine  tliat  all  the  men  stafioned 
in  any  way,  in  or  about  the  magazine,  embracing  all  stationed 
witliin  the  magazine-screen,  put  on  the  magazine-dress  and 
shoes,  and  on  no  account  liave  anything  metallic  about  them, 
and  that  no  improper  articles  are  introduced ; and  to  see  that 
all  the  articles  required  for  sweeping  and  removing  loose  powder 
are  at  hand,  and  that  these  operations  are  performed  before  the 
magazine  is  closed. 

The  tanks  are  never  to  be  opened  unless  by  special  order, 
or  when  powder  is  actually  required  for  service,  and  then  no 
more  of  the  lids  are  to  be  unscrewed  than  the  immediate  supply 
necessitates.  The  strictest  attention  to  this  is  rec[uired,  as  ex- 
perience has  proved  that  the  preservation  of  the  powder  in 
good  condition  depends  upon  the  entire  exclusion  of  damp 
air. 

No  coopering  is  ever  to  be  done  in  the  magazines  of  ships. 
Should  powder  be  received  on  board  in  barrels,  the  hoops  and 
heads  must  be  started  on  the  orlop,  or  berth-deck,  before  enter- 
ing the  magazine. 

1371.  Dampness  of  Magazine. — Sponge  dipped  in  a solu- 
tion of  salt  water,  dried  and  weighed,  is  a means  of  ascertaining 
if  dampness  exists  in  these  places.  If  it  becomes  heavier  the 
magazine  is  damp. 

Ventilation. — Provision  must  be  made  by  means  of  grat- 
ing-hatches for  sufficient  ventilation  in  action,  to  supply  the 
men  with  fresh  air,  and  allow  the  dampness  caused  by  perspira- 
tion to  pass  off ; and  fan-blowers  are  to  be  fitted  to  increase  the 
supply  of  fresh  air,  and  to  assist  the  v^entilation.  The  magazine 
should  be  opened  and  aired  at  least  once  a fortnight,  for  a few 
hours,  on  bright,  clear  days. 

1372.  Magazine  Screens. — They  are  made  of  thick  fear- 
naught  or  double-baize,  with  holes  through  which  to  pass 
the  powder ; these  holes  to  be  covered  with  fiaps  of  the  same 
material.  One  screen  is  to  be  hung  abaft,  and  another  forward 
of  the  magazine  passing-hatch,  and  scuttles  in  sloops-of-war ; in 
frigates,  one  is  usually  hung  abaft  the  fore,  and  one  forward  of 
the  after  magazine-scuttle;  but  as  ships  are  differently  ar- 
ranged, two  to  each  magazine  are  allowed,  if  they  are  neces- 
sary. 

1373.  Transpoktation  of  Powder. — Barrels  of  powder 
should  not  be  rolled  for  transportation  ; they  should  be  carried 
in  hand-barrows,  or  slings  made  of  rope  or  leather.  In  moving 
powder  in  the  magazine  a cloth  or  carpet  should  be  spread ; 


510 


NAVAL  OKDNANCE  AND  GUNNERY. 


all  the  implements  used  there  should  he  of  rrood  or  copper, 
and  the  barrels  should  never  be  repaired  in  the  magazine. 

When  it  is  necessary  to  roll  the  powder  for  its  better  preser- 
vation, and  to  prevent  its  caking,  it  should  be  done  with  a small 
cpiantitj  at  a time,  on  boards  in  the  magazine  yard. 

In  wagons,  barrels  of  powder  must  be  packed  in  straw, 
secured  in  such  a manner  as  not  to  rub  against  each  other,  and 
the  load  covered  with  thick  canvas.  In  transportation  by 
railroad,  each  barrel  should  be  carefully  boxed,  and  packed  so 
as  to  avoid  all  friction.  The  barrels  should  have  a thick  tar- 
paulin under  them.  The  cars  should  have  springs  similar  to 
those  of  passenger-cars. 

1374.  V essels-of-war  always  receive  their  powder  and  loaded 
shell  in  the  stream. 

When  receiving  powder  the  red  flag  is  always  to  be  hoisted 
at  the  fore,'  and  all  proper  precaution  taken  to  guard  against 
accidents  from  fires  and  lights.  The  tanks  should  be  passed 
through  the  ports  most  convenient  to  the  magazines,  and 
landed  on  mats  to  prevent  injiiry. 

The  red  flag  is  always  to  be  hoisted  at  the  powder-houses 
when  they  are  open,  and  kept  flying  until  they  are  closed. 

Tlie  wharf  or  landing-place  must  be  spread  with  old  canvas, 
so  that  the  barrels  or  tanks  may  not  come  in  contact  with,  and 
convey,  sand  or  gravel  to  the  magazines. 

When  avoidable,  gunpowder  is  not  to  be  sent  from  vessels 
to  powder-houses,  nor  from  powder-houses  to  vessels,  in  wet 
weather,  nor  when  there  is  a probability  of  wetting  the  ban-els 
or  tanks ; and  the  packages  must  be  conveyed  in  covered  boats 
or  wagons  showing  a red  flag. 

The  powder-boat,  before  being  used,  must  be  swept  thor- 
oughly clean,  and  the  bottom  covered  with  mats. 

Before  shipping  powder  by  a vessel,  the  hold  must  be  ex- 
amined to  see  that  all  iron  bolt-heads,  etc.,  are  covered  with 
sheet  lead,  leather,  or  old  canvas  ; that  the  hold  is  clean  swept 
and  free  from  grit  or  dust. 

A cushion  (stuffed  with  oakum)  covered  with  leather  is  to 
be  used  for  landing  all  powder  barrels  or  tanks  upon,  whether 
in  the  hold  of  a vessel,  or  on  a wharf,  when  loading  or  dis- 
charging powder. 


Section  V. — Explosive  Compounds. 

1375.  Genekal  Consideratioxs. — Numerous  as  have  been 
the  attempts  to  apply  other  explosive  agents  as  substitutes  for 


EXPLOSIVE  COJIPOtnSTDS. 


511 


gunpowder  in  fire-arms,  no  rival  of  the  latter  has  established 
any  good  claims  to  success  as  a prop>elling  agent,  except  for 
sporting  pui-poses. 

The  various  fulminating  substances  known  to  chemists  are 
unfit  for  use  in  fire-arms,  owing  to  a variety  of  circumstances ; 
one  of  which  is  the  extreme  rapidity  of  their  explosion,  the 
vdiole  mass  appearing  to  be  converted  into  gas  at  once.  The 
action  of  fulminates  is  also  too  local ; if  a portion  of  any  of  the 
more  violently  explosive  substances  be  fired  on  a jriece  of  metal, 
the  latter  will  be  perforated  or  depressed  exactly  at  the  spot 
occupied  by  the  substance ; and  if  it  be  attempted  to  use  it  to 
clrarge  fire-arms,  they  will  be  destroyed,  yet  in  all  probability 
the  ball  not  projected ; moreover,  these  substances  are  not  ser- 
viceable for  charging  shells,  because  the  latter,  instead  of  being 
blown  into  pieces  of  moderate  size  capable  of  inflicting  great 
damage,  become  converted  into  fragments  so  small  as  to  be  far 
less  destructive. 

But,  although  gunpowder  is  still  the  only  propelling  agent 
susceptible  of  general  application,  it  no  longer  enjoys  a mo- 
nopoly in  connection  with  some  equally  important  applications 
to  naval,  military,  and  industrial  purposes,  such  as  blasting, 
demolition  of  walls,  buildings,  or  wrecks,  and  destruction  of 
vessels  by  torpedoes. 

1376.  GUbT-COTTOI^.’'^ — This  is  obtained  by  the  action  of 
concentrated  nitric  acid  on  cotton.  Cotton  is  nearly  pure  cel- 
lulose, which  is  the  principal  part  of  the  ligneous  fibre  or 
woody  matter  of  plants.  Cotton,  linen,  and  hemp  fabrics  and 
unsized  white-paper  are  nearly  pure  cellulose. 

When  cellulose,  cotton  wool  for  instance,  is  acted  upon  by 
a strong  mixture  of  nitric  and  sulphuric  acids,  its  external  ap- 
pearance remains  unchanged,  but  its  chemical  composition  is 
very  much  altered,  being  formed.  This  is  a nitro- 

substitution  prodirct.  A certain  n;nnber  of  equivalents  of  hy- 
drogen being  abstracted  from  the  cellulose,  and  their  place  sup- 
plied by  an  equal  number  of  equivalents  of  nitryl. 

There  are  a number  of  these  substitution  prodircts  in  which 
the  substitution  is  more  or  less  complete,  and  they  differ  more 
or  less  in  their  pi’operties. 

The  pyroxyline  used  to  make  collodion  is  a mixture  of 
several  of  the  lower  ones.  The  lower  products  decompose 
more  readily  than  the  higher  ones,  and  at  a lower  temperature 
they  are  more  prone  to  spontaneous  decomposition  and  more 
inhammable,  and  will  explode,  but  with  less  violence  than  the 
higher  ones. 


* EUl. 


512 


NAVAL  OEDNANCE  AND  GUNNERY. 


The  term  Gun-cotton  slionld  he  restricted  to  the  liighest 
one  of  the  products ; and  in  making  it,  the  substitution  must 
be  carried  as  far  as  possible,  so  that  none  of  the  lower  and  less 
stable  compounds  may  be  obtained  mixed  with  the  higher  ones. 
The  cotton  used  must  be  perfectly  dry,  and  free  from  grease 
or  other  impurities.  Only  the  very  strongest  nitric  acid  must 
be  used,  and  the  treatment  must  be  prolonged  until  the  conver- 
sion has  become  complete.  The  gun-cotton  must  be  finally 
freed  from  every  particle  of  acid. 

1377.  Manufacture. — The  various  details  connected  with 
the  manufacture  of  gun-cotton  are  frecpiently  changing,  and, 
therefore,  only  a general  description  of  the  mode  of  prepara- 
tion will  be  given. 

1378.  Purification  of  the  Cotton — Long-staple  raw 
cotton  of  the  finest  quality  is  the  best  to  use.  It  is  first  cleaned 
and  then  w^ashed  in  an  alkaline  solution  to  get  rid  of  all  oily 
matters,  which  would  otherwise  prevent  the  complete  saturation 
of  the  cotton  by  the  acids  used  in  its  preparation.  xVfter  being 
purified,  it  must  be  again  thoroughly  washed  and  then  dried 
before  going  through  the  subsequent  operations. 

1379.  Treatment  with  Acid. — The  perfectly  dry  cotton 
is  converted  into  gun-cotton  by  immer.sion  in  a mixture  of 
strong  nitric  and  sulphuric  acids,  in  the  proportion  by  weight  of 
one  part  of  nitric'to  three  parts  of  sulphuric  acid. 

The  sulphuric  acid  does  not  act  at  all  in  forming  the  gun- 
cotton, but  only  takes  up  the  Avater  that  is  formed  during  the 
process,  thus  preserving  the  strength  of  the  nitric  acid.  The 
nitric  acid  is  of  the  strength  not  less  than  spec.  grav.  1.50.  The 
sulphuric  acid  is  the  ordinary  oil  of  vitriol,  spec.  grav.  1.83. 

The  cotton  is  fiijst  dipped  in  this  mixture,  and  exposed  to 
its  action  for  a feAV  moments.  It  is  then  taken  out,  and  as 
much  as  possible  of  the  acid  that  has  been  taken  up  removed 
by  pressure.  It  is  then  put  in  fresh  acid,  Avhere  it  I’emaini 
48  hours.  The  vessels  are  kept  cool  during  this  time  by  a 
stream  of  cold  water.  In  the  first  acid  the  cotton  is  nearly  all 
converted,  but  it  is  a matter  of  the  greatest  importance  that  the 
coiiAmrsion  should  be  complete.  It  is  therefore  necessary  that 
the  second  and  prolonged  operation  should  be  made. 

1380.  To  Remoa'e  the  Acid. — To  remove  all  the  acid  from 
the  gun-cotton  thus  made,  it  is  jdaced  m a centrifugal  drying 
machine,  and  then  thoroughly  steeped  for  a^  considerable  time 
in  running  Avater,  and  subsequently  dried. 

It  is  finally  treated  Avith  an  alkaline  solution,  as  carbonate  of 
soda,  and  again  Avashed,  thoroughly  dried,  and  packed. 

1381.  Abel’s  Method. — In  the  manufacture  of  gun-cotton. 


EXPLOSIVE  COMPOUXDS. 


513 


there  is  great  difficulty  in  thoroughly  washing  the  cotton,  be- 
cause the  long,  hollow  fibres  get  twisted  and  bent,  so  that  it  is 
very  hard  to  free  them  from  the  acid.  Abel  has  instituted  the 
pulping  process,  by  which  the  cotton  is  so  torn  as  to  be  easily 
washed ; and  instead  of  raw  cotton  of  high  quality  and  long 
staple,  any  description  of  cotton  can  be  employed;  and  the 
waste  cuttings  from  spinning-machines,  such  as  are  used  for 
cleaning  machinery,  are  more  suitable  than  cotton  in  any  other 
form.  The  pure,  fine  pulp  is  pressed  into  compact  masses 
while  wet. 

1382.  Pulping.  — The  cotton,  after  being  washed  and 
strained,  is  carried  to  a long  tub,  or  heater,  filled  with  water,  in 
which  a wheel  revolves,  armed  on  its  periphery  with  steel  cut- 
ters. From  the  bottom  of  the  tub  under  the  wheel  extend  sim- 
ilar projections  of  steel,  and  as  the  motion  of  the  wheel  carries 
the  cotton  around,  all  parts  are  driven  through  the  contracted 
space  between  the  cutters,  thus  reducing  the  whole  to  a pulp. 
From  the  beater  the  entire  contents  is  run  into  poacher,  or 
large  tub  in  which  a paddle-wheel  revolves.  The  object  being 
to  continue  the  washing  of  the  cotton,  after  being  reduced  to 
pulp,  so  as  to  secure  the  perfect  cleansing  of  the  material.  All 
parts  of  the  pulp  are  carried  over  and  over  by  the  wheel,  and 
this  operation  is  continued  several  hours.  The  operations  of 
the  preparation  of  the  cotton  are  now  complete,  and  it  only  re- 
mains to  di'ain  off  the  water  and  press  the  pulp  into  the  required 
shape. 

1383.  Compressing . — In  order  to  drain  off  the  water,  the 
first  operation  is  to  draw  off  the  pidp  and  water  from  the 
poacher  to  a large  n-on  cylinder,  or  stuff-chest,  where  it  is  agi- 
tated by  paddle-wheels.  From  the  bottom  of  the  stuff-chest 
there  runs  a pipe  to  lead  the  pulp  to  the  press  for  forming  the 
cakes. 

This  press  is  a circular  machine  consisting  of  a shelf  having 
thirty-six  circular  perforations  about  two  and  a half  inches  in  di- 
ameter, which  have  cylindrical  continuations  extending  about  one 
foot  below.  Beneath  these  hollow  cylinders  are  a corresponding 
number  of  solid  cylinders  fitted  so  as  to  enter  them,  which  are 
attached  to  a plate  that  is  actuated  from  below  by  a hydraulic 
force.  The  solid  cylinders  being  entered  into  their  correspond- 
ing hollow  ones,  the  pulp  is  allowed  to  run  in  through  a mova- 
ble trough,  and  fill  the  recesses.  The  upper  orifices  are  now 
covered  with  a weight,  the  solid  cylinders  forced  up,  and  the 
pulp  compressed,  tlie  water  being  allowed  to  escape  through 
strainers  or  perforations  in  the  pressing  cylinders. 

The  cylinders  of  gun-cotton  thus  formed  are  removed  to  a 
33 


514 


NAVAL  ORDNANCE  AND  GUNNERY. 


second  press  having  only  fonr  cylindrical  recesses,  in  each  of 
which  are  placed  three  of  the  cylinders,  separated  from  one 
another  hy  disks  of  iron  having  scored  edges  to  allow  the  escape 
of  water.  The  operation  is  repeated,  the  pressure  being  six 
tons  to  the  sqnare  inch.  This  press  produces  cylinders  about 
three  inches  in  length  hy  two  and  one-half  inches  in  diameter, 
and  weighing  one-half  pound ; about  six  per  cent,  of  moisture 
being  still  retained. 

1384.  General  Properties. — Gun-cotton  is  entirely  insol- 
uable  and  unaffected  by  water,  so  it  may  remain  in  it  any  length 
of  time  without  injury.  Its  permanency  has  been  a matter  of 
doubt,  and  for  this  reason  the  more  extended  use  of  gun-cotton 
has  been  greatly  hindered.  Of  course  if  it  is  liable  to  spontaneous 
decomposition,  it  cannot  he  used  with  any  degree  of  confidence, 
hut  the  late  improvements  in  its  manufacture  seem  to  give  a 
very  stable  and  safe  product.  If  so  regarded,  it  possesses  many 
advantages  over  gunpowder,  as  follows  : less  danger  in  making ; 
unaffected  by  moisture,  or  even  immersion  in  water ; easier 
transportation  ; it  leaves  no  residue  and  makes  no  smoke. 

1385.  Forms  in  which  Ghn-cotton  is  Used. — It  can  he 
worked  into  many  forms  for  different  uses.  The  process  of 
manufacture  when  not  pulped  leaves  it  in  the  loose  state,  re- 
sembling ordinary  cotton.  It  can  then  be  run  into  threads 
and  ropes,  and  the  threads  into  webs  or  hollow  cylinders.  For 
ordnance  purposes  it  is  made  into  disks  from  the  pulp,  or  the 
yarn  is  wound  on  a hollow  tube  or  core.  Besides  this,  the  com- 
pact masses  pressed  from  pulp  can,  while  still  moist,  be  cut, 
saw’ed,  or  drilled  into  any  shape,  granulated  or  mixed  with  other 
bodies. 

Potassium  nitrate  or  chlorate,  is  usually  mixed  with  the 
pulped  article.  Abel  has  proposed  a mixture  called  Glyoxiline 
composed  of  compressed  nitrated  gun-cotton  saturated  with 
nitro-glycerine. 

1386.  Uses  oe  Ghn-cotton. — It  is  much  used  for  mining 
purposes  and  submarine  explosions,  since  it  is  more  readily 
handled  than  gunpowder,  is  not  injured  by  water,  and  less  is 
required  to  do  the  same  work.  Compressed  gun-cotton  is  much 
used  for  torpedoes  and  large  engineering  operations,  for  which 
it  presents  very  gi-eat  advantages.  It  is  very  effective  when 
great  destructive  effects  are  to  be  produced  very  quickly,  as 
blowing  up  bridges  and  military  works.  For  instance,  to  de- 
.‘^troy  a bridge  it  is  only  necessary  to  place  upon  it  a charge  of 
gun-cotton  and  fire  it  with  a detonating  fuze.  In  the  same  way 
large  (piantities  of  rock  may  be  broken  up  and  guns  may  be 
disabled. 


EXPLOSIVE  COMPOUNDS. 


515 


1387.  Mode  of  Firing. — Dry  gun-cotton  when  nneonfined 
flashes  off  without  explosion  ; when  ignited,  therefore,  to  obtain 
its  force  it  must  be  confined  in  strong  vessels  so  that  the  gases 
first  generated  will  he  driven  through  the  whole  mass  envelop- 
ing every  particle  with  flame  before  the  case  is  ruptured.  Under 
these  circumstances  great  explosive  effects  may  he  obtained. 
The  explosion  is  very  much  influenced  by  the  manner  in  which 
it  is  effected.  It  can  be  readily  detonated,  and  then  it  is  un- 
necessary to  have  it  strongly  confined.  The  more  powerfully 
it  is  compressed  the  more  readily  it  can  be  detonated,  since  the 
particles  are  less  able  to  move  on  one  another,  and  therefore 
offer  a greater  resistance,  causing  more  rapid  evolution  of  heat. 

Compressed  gun-cotton  can  be  fired  while  moist,  or  even 
when  saturated  with  water,  by  exploding  in  it  a disk  of  the  dry, 
by  means  of  a fulminate  fuze.  AV^hen  dry  and  unconfined,  if 
ignited  by  a flame,  it  burns  steadily  and  quietly  until  consumed  ; 
but  if  fired  by  a detonator,  it  explodes  violently. 

1388.  UITRO-GLYCEEINE. — This  is  a nitro-substitution 
product  of  glycerine  ; it  is  a violently  explosive  substance  pro- 
duced by  the  action  of  nitric-acid  on  glycerine. 

Its  formation  resembles  that  of  gun-cotton,  three  equivalents 
of  hydrogen  being  removed  frotn  the  glycerine  by  the  nitric 
acid,  and  three  equivalents  of  nitre  introduced  in  their  place. 

1389.  Gdyoeeine  is  the  sweet  principle  of  oils  and  fats. 
It  is  a sweet,  viscid,  colorless  liquid,  soluble  in  water  and  alco- 
hol in  all  proportions.  In  this  country  it  is  principally  derived 
from  the  fats  of  hogs.  That  of  commerce  contains  more  or  less 
water,  and  is  slightly  colored.  Sometimes  it  also  contains  small 
quantities  of  fatty  acids.  This  is  a very  dangerous  impurity,  if 
it  is  to  be  used  in  making  nitro-glycerine,  and  must  be  guarded 
against. 

1390.  Method  of  ManijFxVctuee. — It  is  produced  by  the  ac- 
tion of  strong  nitric-acid  on  glycerine  at  a low  temperature. 

As  in  making  gun-cotton,  the  nitric-acid  is  mixed  with  a 
large  proportion  of  strong  sulphuric  acid, — one  part  of  the  for- 
mer to  two  parts  of  the  latter,  by  weight, — which  acts  in  taking 
up  the  water  that  results  from  the  reaction,  and  so  keeps  the 
nitric  acid  at  its  full  strength. 

Glycerine  is  mixed  slowly  with  the  acid  mixture,  which  is 
constantly  agitated  during  the  operation,  and  great  pains  is 
taken  to  keep  down  the  temperature.  AVhen  all  the  glycerine 
has  been  added,  the  mixture  composed  of  nitro-glycerine  and 
the  remaining  acid  is  poured  in  a thin  stream  into  a large  vol- 
ume of  water,  where  the  nitro-glycerine  is  precipitated  as  a 
white,  opaque,  heavy  oil.  AVhen  it  has  subsided  the  water  may 


516 


NAVAL  ORDNANCE  AND  GUNNERY. 


be  poured  off.  It  must  be  thorougUj  washed,  as  too  much 
stress  cannot  be  laid  upon  the  importance  of  a complete  removal 
of  the  acid  from  the  nitro-glycerine. 

After  some  time,  depending  on  the  temperature,  the  white, 
opacpxe,  thick  fluid  changes  to  a clear,  pale  amber,  somewhat 
thinner  liquid,  and  then  should  be  entirely  free  from  acid.  If 
so,  it  Avill  x-emain  unaltex’ed,  not  becoming  acid  again. 

Converting  glycerine  into  nitro-glycerine  must  be  carefully 
and  properly  conducted,  if  good  results  are  to  be  obtained.  It 
must  be  carried  on  at  as  low  a temperature  as  possible,  and  a 
gi-eat  rise  of  temperature  must  be  prevented  during  the  opera- 
tion. The  glycerine  must  be  free  from  dangerous  impurities. 

The  strongest  nitric  acid  must  be  used  ; if  weak  acid  is  used, 
the  quality  of  the  product  may  greatly  vary. 

1391.  General  Properties. — Nitro-glycerine  is  more  vio- 
lent in  its  explosive  effects  than  gun-cotton,  more  nearly  re- 
sembling the  fulminates,  though  not  so  easily  exploded.  When 
not  piu’e,  it  undei’goes  spontaneous  decomposition  with  evolu- 
tion of  nitrous  fumes,  frequently  causing  explosions ; but  when 
well  purified,  it  may  be  kept  for  a long  time  without  alteration. 

It  is  unaffected  by,  and  does  not  mix  with,  water,  so  that  it 
can  be  exploded  when  in  direct  contact  with  it.  It  is  a light 
yellow,  oily  liquid,  has  a faint,  peculiar  smell,  and  a sweet,  pun- 
gent aromatic  taste.  A drop  of  it  is  said  to  cause  veiy  violent 
headache,  and  in  large  doses  it  appears  to  be  decidedly  poison- 
ous. 

1392.  Mode  of  Firing. — To  explode  nitro-glycerine  it  is 
necessary  to  use  what  is  technically  called  & strong  exjglodcr.  that 
is,  one  that  in  itself  gives  a strong  blow  or  shock.  Therefore, 
fulminate  of  mercury  is  generally  employed  for  that  purpose. 
Nitro-glycerine  explodes  only  locally  by  percussion.  If  placed 
upon  an  anvil  and  struck  with  a hammer,  the  particles  receiving 
the  blow  detonate,  not  exploding,  but  scattering  the  rest  of  it. 
It  is  not  exploded  hy  friction  or  concussion  in  the  ordinary  sense 
of  the  words,  that  is,  by  an  ordinary  or  reasonable  friction  or 
concussion.  Simple  application  of  flame  will  not  fire  it,  though, 
of  course,  it  may  be  heated  to  explosion ; but  it  is  not  sensitive, 
that  is,  not  easily  exploded  by  slight  causes,  therefore  an  ordi- 
nary fuze  or  slow  match  is  useless. 

However  exploded,  it  seems  always  to  be  instantaneous 
through  the  whole  mass.  When  fulminate  is  used,  this  is  evi- 
dently by  direct  detonation.  In  other  cases,  probably  by  initial 
detonation  of  a small  particle.  It  is  more  easil}"  detonated 
than  any  other  body,  and  less  fulminate  is  required.  It  can 
readily  be  fired  by  this  means,  when  imconfined ; but  as  is  al- 


EXPLOSIVE  COMPOUNDS. 


517 


ways  the  case,  greater  effects  are  obtained  if  it  is  confinech 
however  slightly.  It  is  with  the  greatest  difficulty  that  it  is 
bred  when  frozen  ; therefore  it  is  used  in  the  liquid  state. 

1393.  Teanspoetatiojst. — It  is  usually  kept  in  cans  and 
frozen  for  transportation  or  preservation,  and  must  be  melted 
before  it  is  used.  It  solidifies  at  40°  Fahr.,  which  can  readily 
be  accomplished  by  keeping  it  in  melting  ice  a sufficient  time. 
It  freezes  to  a nearly  pure  white  crystalline  mass.  When  frozen, 
it  can  be  melted  by  means  of  hot  water  not  above  90°  or  100° 
Fahr. 

1394.  Stability  oe  Peemanence. — The  history  of  nitro- 
glycerine closely  resembles  that  of  gun-cotton.  The  manufac- 
ture has  been  carried  on  before  it  had  been  properly  studied  or 
its  characteristics  known.  As  to  its  stability,  the  little  exact 
knowledge  obtained  of  it  has  caused  the  opinion  to  be  formed 
that  it  is  very  unstable.  Even  yet  we  have  very  little  precise 
knowledge  of  it,  but  it  is  believed  that  its  permanency  depends 
upon  its  purity,  and  that  if  pure  and  well  made  it  is  sufficiently 
stable,  provided  proper  care  is  taken  of  it.  As  an  explosive  it 
is  so  valuable  that  it  would  still  be  used  even  were  it  much  more 
dangerous. 

1395.  Uses  of  ISTirEo-GLYCEEixE.— It  has  generally  been 
used  for  submarine  and  other  blasting.  For  heavy  work  it 
surpasses  any  other  agent,  being  so  much  more  powerful  than 
gunpowder;  less  is  required  and  less  drilling  is  necessary.  It 
is  a powei-ful  shattering  agent,  and  breaks  up  the  rocks  finehx 
It  leaves  no  residue  and  gives  no  smoke.  It  is  well  adapted  to 
many  kinds  of  submarine  work ; good  results  are  obtained  by 
placing  it  on  the  surface  of  rocks  under  water,  the  latter  acting 
as  a tamping. 

1396.  COMPOUFIDS  OF  XITKO-GLYCEPmE.— The 
successful  application  of  the  remarkable  explosive  liquid,  nitro- 
glycerine, has  been  developed  chiefly  in  the  last  few  years,  and  the 
existence  of  several  most  serious  obstacles  to  its  use  in  the  pure 
liquid  condition  has  been  practically  demonstrated  ; in  several  in- 
stances,.indeed,  by  most  disastrous  accidents;  therefore,  many 
attempts  have  been  made  to  devise  some  method  of  promoting 
safety,  and  also  certainty  of  action  in  its  employment. 

These  ends  have  been  attained  to  a great  extent  by  mixing 
nitro-glycerine  with  some  solid  substance  of  perfectly  inert  na- 
ture, and  of  absorbent  character,  through  the  medium  of  which 
the  liquid  is  susceptible  of  employment  in  a condition  assimi- 
lating to  that  of  other  explosive  agents  in  practical  use. 

1397.  Dynamite. — This  is  the  name  given  to  a compound 
of  nitro-glycerine  formed  by  absorbing  it  in  a light  silieious 


518 


NAVAL  ORDNANCE  AND  GUNNERY. 


earth,  which  may  he  mixed  with  about  three  times  its  weight  of 
uitro  glycerine  without  becoming  more  than  moist  to  the  touch, 
and  is  therefore  readily  susceptible  of  manipulation  as  a solid 
material.  This  mixture  is  as  readily  susceptible  of  explosion 
through  the  initiative  agency  of  a detonating  fuze  as  nitro-gly- 
cerine  itself,  and  though  it  obviously  cannot  he  so  powerful  an 
explosive  agent  as  that  substance  when  successfully  applied  in 
its  undiluted  state,  its  destructive  powers  are  still  greatly  in  ex- 
cess of  those  of  gunpowder. 

Dynamite  is  applicable  to  all  the  uses  for  which  nitro-gly- 
cerine  is  employed.  When  properly  applied  it  does  nut  need 
confinement  for  the  development  of  its  explosive  forces,  and 
it  is  especially  applicable  for  military  purposes. 

It  is  by  far  the  best  of  the  nitro-glycerine  mixtures,  and  is 
probably  the  best  form  for  its  use  in  torpedoes. 

Certain  defects  are  inherent  in  the  material,  such  as  its  los- 
ing its  susceptibility  to  detonation  by  the  ordinary  means  at  a 
low  temperature,*  and  the  tendency  of  the  nitro-glycerine  to 
partial  separation  from  the  silicious  earth  during  transport 
and  storage ; hut  in  balancing  its  advantages  against  those  of 
other  explosive  agents,  the  special  defects  of  these  have  also  to 
he  taken  into  account,  so  that,  provided  the  uniform  stability  of 
the  material  becomes  established,  and  the  apprehensions  as  to 
its  comparatively  dangerous  character,  to  which  certain  accidents 
have  given  rise,  are  allayed  by  further  experience  in  its  storage 
and  use,  and,  possibly,  by  improvements  in  its  manufacture,  a 
high  position  may  be  assigned  to  dynamite  among  the  most  use- 
ful explosive  agents  of  the  present  time.  It  is  the  best  of  all 
the  nitro-glyceilne  preparations. 

1398.  Lithofracteue. — Several  other  methods  of  applying 
nitro-glycerine  as  a destructive  agent  have  been  brought  for- 
ward. Among  these  is  the  substance  to  which  the  inventor  has 
given  the  name,  lithofracteiir,  and  which  contains,  in  addition 
to  nitro-glycerine  and  an  absorbing  medium  of  the  description 
used  in  dynamite,  some  proportion  of  other  explosive  materials, 
such,  for  example,  as  the  constituents  of  gunpowder.  This  sub- 
stance is  of  a plastic  and  almost  pasty  nature,  and  is  employed 
in  the  form  of  rolls  made  up  in  paper. 

Lithofracteur  may  be  considered  a dynamite  to  which  has 
been  added  about  twenty  per  cent,  of  bad  gunpowder  contain- 
ing an  enormous  excess  of  carbon.  The  addition  of  the  con- 
stituents of  gunpowder  lowers  its  tiring-point,  which  is  of 

* If  finely  divided,  it  may  be  exploded  when  frozen  ; but  this  fact  is  practi- 
cally of  Uttle  value. 


EXPLOSIVE  COMPOUNDS. 


519 


doubtful  advantage  and  makes  it  more  liable  to  be  injured  by 
moisture.  Its  force  must  be  less  than  dynamite,  for  it  depends 
on  the  amount  of  nitro-glycerine  in  it ; no  additional  force  be- 
ing derived  from  the  other  ingredients. 

1399.  Dualixe. — Sawdust  and  similar  absorbent  materials 
have  also  been  used  as  vehicles  for  the  application  of  nitro-gly- 
cerine, under  the  name  of  dualine. 

This  mixture  also  contains  about  twenty  per  cent,  of  saltpe- 
tre. It,  however,  owes  its  explosive  qualities  to  the  uitro-glyce- 
rine,  and  the  only  thing  in  its  favor  is  that  it  is  not  liquid.  In 
other  respects  there  are  serious  objections  to  it.  The  slight  ab- 
sorbent power  of  the  sawdust  makes  the  amount  of  nitro-glyce- 
rine taken  up  comparatively  small,  while  holding  feebly  what 
is  absorbed.  The  mixture  of  nitre  and  wood  makes  dualine 
more  sensitive  to  flame  or  blows,  and  lowers  the  tiring-point. 
It  contains  less  nitro-glycerine  tlian  dynamite,  and  hence  is 
weaker.  It  is  much  lighter  than  dynamite,  and  for  equal  vol- 
umes has  much  less  force.  It  has  an  excess  of  carbon  from  the 
wood,  so  that  great  amounts  of  that  deleterious  gas,  carbonic-ox- 
ide, are  formed,  diminishing  the  force  of  the  reaction. 

1400.  FULMINATES. — Fulminate  is  the  general  name  for 
a class  of  explosive  bodies  which  are  compounds  of  fulminic 
acid  with  a base.  They  are  all  more  or  less  explosive  by  the 
action  of  heat  or  friction  ; of  these  the  fulminates  of  mercury 
and  silver  are  the  most  important. 

1401.  Fulmixate  of  Mekcuey  is  prepared  by  dissolving 
one  part  of  the  mercury  in  twelve  of  nitric  acid,  sp.  gr.  1.42, 
aided  by  a gentle  heat.  As'  soon  as  the  mercury  is  dissolved 
add  eleven  parts  of  alcohol  sp.  gr.  0.87.  A brisk  action  will 
ensue  and  the  solution  will  become  turbid  from  the  separation 
of  crystals  of  the  fulminate.  Dense,  white  clouds  are  also 
evolved  at  the  same  time.  When  the  action  has  subsided  the 
vessel  may  be  filled  with  water  and  the  fulminate  allowed  to 
settle,  after  which  it  is  collected  on  a filter,  washed,  and  dried 
by  exposure  to  the  air.  When  dry,  it  must  be  handled  cau- 
tiously, as  it  explodes  by  friction  or  percussion,  especially  when 
in^contact  with  particles  of  sand  or  glass.  It  is  also  exploded 
by  heating  to  about  300°,  by  the  electric  spark  and  by  contact 
with  concentrated  nitric  acid  or  sulphuric  acid. 

When  wet  it  will  not  explode.  Its  explosive  force  is  not 
much  greater  than  that  of  gunpowder,  but  it  is  much  more  sud- 
den in  its  action. 

The  readiness  with  which  it  is  fired  makes  it  an  excellent 
agent  for  exploding  other  substances,  and  this  gives  it  its  value. 
It  is  used  in  percussion-caps,  primers,  and  fuzes — not  pure,  but 


520 


NAVAL  OEDNANCE  AND  GUNNEET, 


mixed  with  nitre,  mealed-powder,  and  other  substances,  because 
it  is  necessary  to  moderate  its  explosive  property,  since  it  is 
otherwise  too  rapid  and  violent  for  the  purpose.  It  is  some- 
times mixed  with  chlorate  or  nitrate  of  potash,  and  ground 
glass  is  often  added  to  increase  the  sensibility  of  the  mixture  to 
explosion  by  percussion. 

1402.  Fulminate  of  Silver  is  prepared  by  a process  simi- 
lar to  that  for  fulminate  of  mercury,  but  as  its  explosive  quali- 
ties are  far  more  violent  it  is  advisable  to  prepare  it  only  in 
minute  quantities.  When  dry,  it  must  be  handled  with  the 
greatest  caution.  Notliing  harder  than  paper  should  be  used 
in  manipulating  it,  or  for  Avrappers.  It  is  exploded  in  the  same 
way  as  fulminate  of  mercury,  but  is  of  no  practical  value  on 
account  of  its  sensitiveness. 

1403.  Picric  Acid  and  Picrates. — Picric  Powder. — Picric, 
or  tri-nitrophenic  acid,  is  another  nitro-substitution  compound. 
It  is  formed  by  the  action  of  nitric  acid  upon  phenol,  or  phenylic 
alcohol,  better  known  as  carbolic  acid.  It  is  used  as  a dye-stuff. 
It  has  but  feeble  explosive  properties,  yet  many  of  its  salts  are 
highly  explosive. 

Potassium  picrate  is  so  verj"  sensitive  to  friction  or  percus- 
sion as  to  be  practically  useless. 

Abel’s  picric-powder  is  a mixture  of  ammonium  picrate  with 
saltpetre.  It  is  very  little  affected  by  blows  or  friction,  possesses 
considerably  more  explosive  force  than  gunpowder,  and  can  he 
worked  in  a moist  state  like  ordinary  powder.  It  is  said  to  be 
useful  for  torpedoes. 


CHAPTER  IX. 


PTEOTECHNT. 


Section  1. — Materials.'^ 

1404.  Definition. — Pyrotecliny  is  the  art  of  preparing 
ammunition  and  fireworks  for  military  and  ornamental  jnir- 
poses. 

Buildings. — To  conduct  the  operations  of  tlie  laboratory 
witb  safety  and  convenience,  tbe  following  rooms  are  necessary, 
viz. ; 

1st.  Furnace-room,  for  operations  requiring  tbe  use  of  fire. 

2d.  Cartridge-room , for  making  all  kinds  of  cartridges. 

3d.  Filling-room,  for  filling  cartridges  wdtb  powder. 

4tb.  Con^ositiomroom,  for  mixing  compositions. 

5tb.  Driving-room,  for  driving  rockets,  fuzes,  etc. 

6tb.  PacTiing-^'oom,  for  putting  up  articles  for  transporta- 
tion. 

7tb.  Carpenter' s and  Tinner' s-shop. 

8tb.  Magazine,  for  storing  powder  and  ammunition. 

A laboratoiy,  like  a powder-mill,  should  be  situated  apart 
from  inhabited  buildings  ; and  for  convem'ence  of  communica- 
tion, the  rooms,  with  the  exception  of  the  furnace-room,  carpen- 
ter’s-shop,  and  magazine,  should  be  situated  under  one  roof. 

1405.  Furnaces. — A furnace  is  composed  of  a cast-iron  ket- 
tle 2 feet  in  diameter  set  in  a fireplace  of  brick.  In  the  field, 
sods  may  replace  the  brick,  if  the  latter  cannot  be  obtained. 

Two  kinds  of  furnaces  are  employed  in  a laboratory  ; in  tbe 
first,  the  fiaine  circulates  around  both  bottom  and  sides  of  the 
kettle ; in  the  second,  it  only  comes  in  contact  with  the  bottom  ; 
the  latter  is  used  for  compositions,  in  which  gunpowder  forms 
a part. 

1406.  Precautions. — To  prevent  accidents  in  the  operations 
of  a laboratory,  avoid  as  much  as  possible  the  use  of  iron  in  the 
construction  of  the  buildings,  fixtures,  etc. ; sink  the  heads  of 
iron-nails,  if  used,  and  cover  them  with  putty  ; cover  the  floor 
with  oil-cloth  or  carpets,  and  have  it  frequently  swept.  Let  the 


Benton's  Ordnance  and  Gunnery. 


522 


NAVAL  ORDNANCE  AND  GUNNERY. 


workmen  in  the  powder-room  wear  socks,  and  take  them  off 
when  they  go  out.  Keep  no  more  than  the  requisite  amount 
of  powder  in  the  laboratory,  and  have  the  ammunition  and 
finished  work  taken  to  the  magazine.  Let  powder-barrels  be 
carried  in  hand-barrows  made  with  leather,  or  with  slings  of 
rope  or  canvas,  and  the  ammiinition  in  boxes.  Let  everything 
that  is  to  be  moved  be  lifted,  not  dragged  or  rolled  on  the  floor. 
Never  drive  rockets,  port-flres,  etc.,  in  a room  where  there  is 
any  powder  or  composition  except  that  used  at  the  time. 
Never  enter  the  laboratory  at  night,  xmless  it  is  indispensable, 
and  then  use  a close  lantern,  or  wax  or  oil  light  well  trimmed. 
Allow  no  tobacco  to  be  smokod,  nor  friction-matches  to  be  car- 
ried in  or  around  the  laboratory. 

1407.  Mateeials.— -Laboratory  materials  may  be  divided  in- 
to four  classes,  viz. : 

1st.  Those  for  producing  light,  heat,  and  explosion. 

2d.  Those  for  coloring  flames  and  producing  bnlliant  sparks. 

3d.  Those  used  in  preparing  compositions. 

4th.  Those  used  in  making  cartridge  bags,  cases,  etc. 

1408.  1st  Class. — Nitre.- — For  laboratory  use,  nitre  must 
be  reduced  to  a tine  powder  or  very  minute  crystals.  It  is  best 
pulverized  in  rolling-barrels  at  the  powder-mills,  but  it  may  be 
pulverized  by  hand,  in  the  laboratory,  with  a rolling-barrel,  or 
by  pounding  in  a brass  mortar,  or  by  stirring  a crystallizing  so- 
lution. 

1409.  Chlorate  of  Potassa. — Chlorate  of  potassa  is  formed  by 
passing  a current  of  chlorine,  in  excess,  through  lime-water,  and 
then  treating  the  mixture  with  the  chloride  of  potassium,  or  by 
the  carbonate  or  sulphate  of  potassa.  The  chlorate  of  potassa 
and  chloride  of  calcium  are  formed  ; the  former  crystallizes, 
the  latter  remains  in  solution.  It  is  soluble  in  water,  but  not 
sensibly  so  in  alcohol.  As  before  stated,  it  is  a more  powerful 
oxydizing  agent  than  nitre  ; and  when  mixed  with  a combusti- 
ble body,  easily  explodes  by  shock  or  friction.  It  is  inflamed  by 
simple  contact  with  sulphuiic  acid,  and  thus  affords  a simple 
means  of  exploding  mines. 

A convenient  form  of  apparatus  for  this  purpose  is  a glass 
vmssel  with  two  compartments;  one  containing  sulphuric  acid, 
and  the  other  chlorate  of  potassa  and  gunpowder.  It  is  placed 
near  the  surface  of  the  ground,  and  when  broken  under  the  feet 
of  the  enemy,  the  two  substances  are  brought  in  contact,  pro- 
ducing fire,  which  explodes  the  mine. 

1410.  Charcoal. — For  laboratory  use,  charcoal  may  he  made 
by  charring  wood  in  an  iron  kettle  buried  in  the  ground.  It 
may  be  pulverized  by  rolling  in  a barrel  with  bronze  balls,  or 


PRYOTECHNY. 


523 


by  beating  in  a leatber  bag  with  a maul.  It  slionbl  be  kept  in 
close  barrels  in  a dry  place. 

nil.  Sulphur. — When  melted  sulphur  is  to  be  used,  care 
must  be  taken  that  it  does  not  become  thick,  which  occurs  at 
about  400°,  It  may  be  pulverized  in  a rolling-barrel,  or  by  be- 
ing pounded  in  a mortar  and  sifted.  Eoll  brimstone  is  better 
for  melting  than  flowers  of  sulphur.  When  flowers  of  sulphur 
are  to  be  mixed  wdth  chlorate  of  potassa,  it  should  be  washed 
to  remove  the  free  sulphui'ie  acid.  Sulphur  hastens  the  com- 
bustion of  compositions  to  which  it  is  added. 

1412.  Antimony — Antimony,  or  regulus  of  antimony,  is  a 
grayish-white  metal,  easily  reduced  to  a powder,  and  by  its  com- 
bustion with  sulphur  produces  strong  light  and  heat ; the  color 
of  the  flame  is  a faint  blue. 

1413.  Sulphuret  of  Antimony. — Sulphuret  of  antimony  is 
mixed  with  inflammable  substances  to  render  them  more  easily 
ignited  by  flame  or  friction. 

1414.  Gunpowder. — For  compositions,  gunpowder  is  pulver- 
ized, or  mealed,  by  the  rolling-barrel,  or  by  grinding  with  a 
muller  on  a mealing-table,  or  by  beating  in  a leather  bag.  The 
simple  incorporation  of  the  ingredients  of  gunpowder  does  not 
answer  the  desired  purpose. 

1415.  Lampblack. — Lampblack  is  the  result  of  the  incom- 
plete combustion  of  resinous  substances.  It  is  composed  of 
about  80  parts  of  carbon  and  20  of  impurities.  It  is  employed 
to  quicken  the  combustion  of  certain  mixtures  ; but  before  it  is 
used,  it  should  be  washed  with  a strong  alkaline  solution,  to  re- 
move all  traces  of  empyreumatic  oil. 

1416.  2d  Class. — Coloring  Materials. — Aflame  is  colored 
by  introducing  into  the  composition  which  produces  it  a sub- 
stance the  particles  of  wdiich,  on  being  interspersed  through  the 
flame,  and  heated  to  the  incandescent  state,  give  it  the  recpdred 
color.  Coloring  substances  do  not  generally  take  part  in  the 
combustion,  and  their  presence  more  or  less  retards  it ; it  is  for 
this  reason  that  chlorate  of  potassa,  a more  pow’erful  oxydizing 
agent  than  nitre,  is  used  in  lieu  of  it,  in  compositions  for 
colored  fires. 

1417.  Colors. — There  are  a great  variety  of  substances  which 
give  color  to  flames,  the  principal  of  which  axe  nitrate  and  sul- 
phate of  strontium,  and  chloride  of  strontium,  for  red ; the  ni- 
trate of  barium,  for  green  ; the  bicarbonate  of  soda,  for  yellow  ; 
the  sidphate,  carbonate,  and  acetate  of  copper,  for  blue  Lamp- 
black is  employed  to  give  a train  of  rose-colored  fire  in  the  air; 
powdered  flint-glass,  for  white  flames ; and  oxide  of  zinc,  for 
blue  flames. 


524 


NAVAL  ORDNANCE  AND  GUNNERY. 


1418.  Sj)arhs. — ■Briniant  sparks  are  produced  by  introducing 
into  the  composition  filings  or  thin  chips  of  either  wrought-iron, 
cast-iron,  steel,  or  copper,  or  by  fragments  of  charcoal;  the 
effect  depends  upon  the  si/e  of  the  particles  introduced.  The 
j)articles  should  be  freshly  prepared,  or  shoidd  have  been  -we]! 
preserved  from  rust. 

1419.  3d  Class.  Peepauing  CoMPOsmojrs. — Turpentine  is 
the  substance  which  exudes  from  the  freshly  cut  surface  of  a pine- 
tree  in  warm  weather.  The  first  year’s  running  is  called  virgin, 
or  white,  turpentine  : after  this  it  becomes  more  hard  and  yellow. 

1420.  Spirits  oj  Turpentine. — This  is  the  essential  oil  ob- 
tained by  distilling  native  turpentine. 

1421.  liosin. — This  substance  is  sometimes  called  colo- 
phony., and  is  the  residiuum  of  the  distillation  of  tui-pentine. 

1422.  Tar. — Tar  is  a semi-fluid  substance,  obtained  from 
the  heart  of  the  pine-tree  by  a smothered  combustion,  as  in 
charcoal -pits. 

1423.  Pitch. — Pitch  is  obtained  by  boiling  down  tar  to  the 
requisite  consistency,  either  by  itself  or  combined  with  a por- 
tion of  rosin  ; it  becomes  solid  on  cooling,  but  is  softened  by 
the  heat  of  the  hand. 

1424.  Venice  Pcrpentine. — Yenice  tui’pentine  is  obtained 
from  the  larch ; but  what  is  commonly  known  by  that  n.nne  is  a 
compound  of  melted  rosin  and  spirits  of  turpentine.  The  fore- 
going substances  are  chiefly  employed  in  the  preparation  of 
compositions  for  producing  light. 

1425.  Alcohol,  etc. — Alcohol  (spirits  of  wine),  hrandy,  whtis- 
Tcey,  or  vinegar,  is  used  for  mixing  compositions  in  which  nitre 
enters,  because  this  salt  is  but  slightly  soluble  in  these  liquids. 

1426.  Gum-Arabic.— -Gmxi-^LYSLhic.  in  solution  is  employed 
to  give  body  to  certain  compositions.  It  retards  combustion  ; 
and  as  the  solution  is  liable  to  spontaneous  decomposition,  it 
should  only  be  prepared  as  wanted. 

1427.  Beeswax  and  2£utton-taIlow  are  employed  chiefly  in 
mixing  compositions  intended  to  produce  heat  and  light. 

1428.  4tii  Class. — Pkepaelxg  Caeteddges,  etc. — The  mate- 
rial of  which  cartridge-bags  are  made  is  woven  expressly  for  the 
purpose.  The  color  is  white,  and  the  calibre  of  the  gun  and  the 
weight  of  the  charge  must  be  stencilled  on  the  bag  in  figures 
two  and  a half  inches  long.  AYhen  procured  of  necessity  else- 
where, the  stutf  should  be  chosen  of  wool  entirely  free  from  any 
mixture  of  thread  or  cotton,  and  of  sufficiently  close  texture  to 
prevent  the  finer  powder  from  sifting  through.  'Wild-hoar, 
satinet,  merino,  and  bombazette  are  named  as  proper  materials 
for  cartridge-bags ; of  these  the  thinnest  stuff,  not  twilled,  hut 


PYEOTECHIfY, 


525 


having  the  requisite  strength  and  closeness  of  texture,  is  the 
best.  Fabrics  of  cotton  and  flax  are  not  used,  because  the 
powder  sifts  through  them,  and  they  are  more  apt  to  leave  fire 
in  the  gun  than  Avoollen  stuffs. 

1429.  Compositions. — The  term  composition  is  applied  to 
all  mechanical  mixtures  which  by  combustion  produce  the 
effects  sought  to  be  attained  in  pyrotechny.  If  these  composi- 
tions be  examined,  it  will  be  found  that  many  of  them  are  de- 
rived from  gunpowder,  by  an  admixture  of  sulphur  and  nitre, 
in  proportions  to  suit  the  required  end. 

1430.  Preparation. — Compositions  are  prepared  in  a dry  or 
liquid  form  ; in  either  case  it  is  necessary  that  the  ingredients 
should  be  pure  and  thoroughly  mixed. 

1431.  Yor  dry  compositions,  the  ingredients  are  pulverized 
separately,  on  a mcaliny-tcible,  with  a wooden  midler  y they  are 
then  weighed  and  mixed  with  the  hands,  and  afterwards  passed 
three  times  through  a wire  sieve  of  a certain  fineness.  lYhen 
a highly  oxydizing  substance,  as  the  chlorate  of  potassa,  is 
present,  great  care  must  be  observed  in  mixing  to  a^mid  friction 
or  blows  which  might  lead  to  an  explosion.  When  coarse  char- 
coal or  metals  in  grains  are  used,  they  should  be  added  after 
the  other  ingredients  have  been  mixed  and  sifted. 

1432.  For  the  liquid  form. — When  it  becomes  necessary  to 
use  fire  to  melt  the  ingredients,  the  greatest  precaution  is  nec- 
essary to  prevent  accident,  especially  when  gunpoivder  enters. 
The  dry  parts  of  the  composition  may  be  generally  mixed  to- 
gether first,  and  put  by  degrees  into  the  kettle,  when  the  other 
ingredients  are  fluid,  stirring  well  all  the  time.  When  the  dry 
ingredients  are  very  inflammable,  the  kettle  must  not  only  be 
taken  from  the  fire,  but  the  bottom  must  be  dipped  in  water,  to 
prevent  the  possibility  of  accidents. 

1433.  Foem. — To  give  a portable  form  to  compositions, 
they  are  inclosed  in  eases,  cast  in  moulds,  or  attached  to  cotton- 
yarn,  rope,  etc. 

1434.  Cases. — Cases  are  generally  paper  tubes,  made  by 
covering  one  side  of  a sheet  of 

o 


paper  with  paste,  or  gum-arabic, 
wrapping  it  around  informer,  and 
rolling  it  under  a flat  surface  until 
all  the  layers  adhere  to  each  other. 

The  quality  of  the  paper  and  the 
thickness  of  the  sides  of  the  case 
should  depend  upon  the  pressure 
of  the  gases  evolved  in  the  burning.  (Fig.  314) 

1435.  Filling. — To  fiU  a case,  it  is  first  cut  to  the  proper 


Fig.  314. 


526 


NAVAL  OEDNANCE  AND  GUNNEET. 


length  and  placed  in  a mould ; the  composition  is  then  poured 
in,  a ladleful  at  a time,  and  each  ladleful  is  packed  bj  striking 
a certain  number  of  blows  on  a drift  with  a mallet  of  a given 
weight.  The  height  of  each  ladleful  of  composition  should  he 
about  ecpial  to  a single  diameter  of  the  bore  of  the  case. 

1436.  Drifts^  etc. — Small  drifts  receiving  heavy  blows 
should  he  made  of  steel,  and  tipped  Avith  bronze  (Tig.  315); 
large  di-ifts  may  be  made  of  wood  or  bronze,  depending  on  the 

force  of  the  blow.  In  driving 
highly  inflammable  compositions, 
as  that  of  the  rocket,  care  should 
be  taken  to  settle  the  drift  so  as 
to  exclude  the  air  before  striking 
with  the  mallet,  as  the  heat  gen- 
erated by  the  sudden  condensation  of  air  might  be  euftieient  to 
ignite  the  composition. 

Preliminary  tests  of  all  new  materials  should  he  made  by 
burning  one  or  more  specimens  of  the  composition,  and  the 
proportions  of  the  ingredients  corrected,  if  necessary. 

1437.  Yent. — The  length  of  the  flame  from  a given  compo- 
sition depends  on  the  size  of  the  vent  and  the  extent  of  the 
burning-surface.  The  vent  is  made  small  b}'  chohing  the  end 
of  the  case  with  stout  twine ; and  the  bmaiing-surface  is  in- 
creased by  driving  the  composition  around  a spindle  which,  on 
being  withdrawn,  leaves  a conical-shaped  cavity.  A vent  may 
be  also  formed  by  driving  in  moist  plaster  of  Paris  or  clay,  and 
boring  a hole  in  it  with  a gimlet.  If  the  end  of  the  case  is  to 
he  closed  up  entirely,  the  boring  is  omitted. 


Fig.  315. 


Section  II.— Means  of  Finng  Cannon. 

1438.  Pkimeks. — One  of  the  most  important  subjects  to  he 
considered  in  connection  with  the  efficiency  of  the  ship's  battery, 
is  that  of  providing  a simple  and  efficient  means  of  discharging 
the  guns  instantaneously  and  with  certainty  ; to  this  end  num- 
erous contrivances  and  inventions  have  been  suggested  and 
tried. 

Percussion  and  friction  primers  are  now  used  in  the  ser- 
vice, although  elective  primers,  tubes,  port-tire,  and  slow-match 
are  manufactured,  and  may  be  used  in  special  cases. 

1439.  Pekcussiox-puimees. — The  percussion-primer  has  a 
Avafer  or  flat-head  attached  to  a quill-harrel.  The  process  usu- 
ally observed  in  selecting  the  material  and  manufacturing  the 
primers  is  as  follows  : 


PEIMERS. 


527 


Each  quill  must  be  clarified  and  furnish  a barrel  at  least  two 
and  a half  inches  long.  The  barrel  is  to  be  round,  free  from 
flaws,  pith,  and  brittleness  occasioned  by  clarifying,  or  any  other 
defect  which  may  render  it  unfit  for  the  purpose  required. 
(Flatness  of  the  quill-barrel  will  subject  it  to  be  rejected  at  the 
discretion  of  the  Inspecting  Officer.)  It  must  not  exceed  in 
diameter  nineteon-hundreths  of  an  inch  at  any  part,  nor  be  less 
than  seventeen-hundreths  of  an  inch,  within  one  and  one-half 
inches  of  the  end  that  is  cut  from  the  quill.  The  small  end 
must  not  be  broken  or  bruised. 

1440.  Fabrication. — Cut  the  barrels  of  the  quills  close  from 
the  feather,  aud  insert  them  into  the  socket  of  a wooden  block 
made  two  inches  deep  and  two  tenths  of  an  inch  in  diameter. 

A punch,  having  ten  cutters  radiating 
from  the  stem,  is  entered  into  each  quill- 
barrel,  and  driven  down  with  a smart  tap, 
so  as  to  slit  the  upper  end  of  the  barrel  into 
ten  prongs,  and  as  far  as  the  upper  surface 
of  the  block  permits.  (Fig.  316.)  Turn 
back  the  prongs,  so  that  they  will  lie  on  the 
surface  of  the  block ; a circular  punch  is 
applied  to  each,  and  made  by  a blow  to  cut 
off  the  prongs  to  its  own  diameter  (0.52 
inch). 

1441.  Yery  stout  paper,  previously  pre- 
pared by  tw’o  coats  of  shellac  varnish  (gum- 
lac  dissolved  in  alcohol),  is  punched  witli 
holes  0.17  inch  in  diameter,  and  so  ar- 
ranged as  to  correspond  with  the  sockets  of 
the  wooden  block.  The  quill-lDarrels  are 
freed  from  pith,  the  punched  paper  laid  on 
the  block,  the  holes  corresponding  and  the 
varnished  side  up,  the  quill-barrels  put  Fig.  316. 
through  the  paper  into  the  sockets  of  the 

block,  filled  with  grained  powder,  seven  grains  Troy,  and 
pressed  firmly  down  with  their  prongs  fiat  on  the  varnished 
side  of  the  sheet  of  stout  paper. 

1442.  Brush  the  shellac-varnish  over  the  spaces  of  paper  be- 
tween the  heads  of  the  quill-barrels,  and  spread  a sheet  of  good 
writing-paper,  slightly  moistened  with  water,  over  the  entire 
surface  of  the  stout  sheet  and  the  prongs  of  the  quills.  Put 
the  block  and  the  sheets  thus  stuck  together,  with  the  quill 
prongs  between  them,  into  a pi-ess,  apply  a foi’ce  of  about  thirty 
tons,  and  keep  them  long  enough  to  set  the  prongs  and  make 
the  sheets  of  paper  adhere  firmly. 


528 


NAVAL  ORDNANCE  AND  GUNNERY. 


1443.  Each  quill  is  separated  from  tlie  card  bj  means  of  a 
circular  punch,  which  cuts  out  a disk  0.62  inch  in  diameter, 
and  of  course  includes  the  prongs  enclosed  between  them.  A 
stellated  disk  to  C'over  the  head  of  the  primer  is  punched  out  of 
linen-made  paper  of  the  finest  and  closest  fabric.  This  disk  has 
twelve  points — diameter  from  exterior  points,  1.25  inches,  from 
interior  0.700  inch.  Metal  plates  are  at  hand  with  superficial 
recesses  about  0.65  inches  in  diameter.  On  each  of  these  a 
stellated  cover  is  placed,  and  four  grains  of  fulminate  deposited 
on  it.  This  is  composed  of  five  parts  of  fulminating  mercury 
and  one  of  mealed-powder,  both  dry.  Place  the  head  of  the 
primer  on  the  charge  of  fulminate,  holding  it  by  the  quill-harrel 
and  pressing  it  down  firmly ; brash  good  wLeat  paste  on  the 
points  of  the  cover  and  on  the  interior  surface  of  the  head, 
turn  the  points  over,  and  unite  them  neatly  and  closely  on  the 
paper  head. 

1444.  The  primer  is  now  made  and  only  requires  to  he  pro- 
tected from  moisture.  Eor  this  purpose,  shellac  is  dissolved  in 
alcohol,  so  as  to  he  thin  enough  to  he  laid  on  with  a brash. 

This  is  of  a brownish  yelloAv ; a portion  is  pre- 
pared with  lamp-black.  Coat  over  the  quill-barrel 
with  shellac,  then  the  under  side  of  the  wafer 
with  the  black  shellac-varnish.  Then  shellac  the 
upper  surface  of  the  wafer.  Tip  the  end  of  the 
quill-harrel  with  black  varnish,  and  apply  a second 
coat  of  uncolored  shellac  thickly  about  the  primer. 
(Fig.  317.) 

1445.  The  primers,  being  put  in  tin  boxes  made 
to  hold  fifty  of  them,  are  ready  for  inspection. 
After  which  the  lids  are  coated  with  shellac  to  ex- 
clude moisture,  until  wanted  for  immediate  use. 
These  boxes  are  intended  to  fit  in  and  form  a lin- 
ing to  the  primer-boxes  which  slip  on  the  waist- 
belts  worn  by  the  Gun  Captains. 

1446.  When  primers  have  been  returned  from 
cruising  ships,  or  have  remained  in  store  for  one 
or  more  years,  they  must  he  tested  by  firing  five 

per  cent,  of  the  number,  and  not  issued  again  without  special 
orders. 

The  date  of  manufacture  or  re-inspection,  with  the  initials 
of  inspecting  officer,  are  to  he  legibly  written  and  pasted  Avithin 
the  cover  of  the  laboratory  cases,  and,  when  issued  for  service, 
the  date  and  station  to  which  sent  is  to  he  added. 

1447  FniCTiON-PiirMEKS. — The  friction-primer  for  cannon  is 
a small  brass  tube  1-J  inches  in  length,  and  0.19  inch  in  diam- 


Fig.  317. 


PRniERS. 


529 


eter,  filled  with  fine-grained  powder,  wliicli  is  ignited  by  di-aw- 
ing  a roiigb  wire  briskly  tbrongb  friction  composition  contained 
ill  a smaller  tube  inserted  into  tbe  first  near  the  top,  and 
soldered  at  right-angles  to  it. 

Tbe  short  tube  is  0.44  inch  long,  and  0.15  inch  in  diam- 
eter. The  wire  is  3.4  inches  long,  of  brass,  annealed,  the  end  in 
the  small  tube  flattened,  and  fitted  with  dentated  edges,  a ; 
while  the  other  end  is  doubled  on  itself  and  twisted,  leaving  a 
loop  0.2  inch  in  diameter,  and  then  bent  alongside  the  long 
tube  for  packing.  (Fig-  318.) 

1448.  Friction  Comjyosition. — This  is  made  of  two  parts  of 
the  sulphiiret  of  antimony  and  one  part  of  the  chlorate  of 
potassa  moistened  with  gummed 
water,  50  grains  of  gum-arabic  in 
two  ounces  of  water  to  one  pound 
of  composition.  The  materials 
are  first  pulverized  separately, 
mixed  together  dry,  moistened 
with  gum-water,  and  ground  in 
an  iron  mill  such  as  is  used  for 


I’imers  are  packed 
in  tin  boxes  in  the  same  manner 
as  percussion-primers.  Fra.  318. 

1449.  In  case  either  lock  or 

percussion-primer  should  entirely  fail,  recourse  will  be  had  to 
the  friction-primer.  In  using  them,  the  Gun  Captain,  after 
taking  the  primer  from  the  box,  will  raise  the  twisted  wire 
loop  until  it  is  on  a line  with  the  spur ; place  the  tube  in  the 
vent  with  the  spur  towards  the  muzzle  of  the  gun,  then  hook 
the  lanyard  into  the  raised  loop,  and  pull  it,  when  otherwise 
ready  to  fire ' the  gun,  as  though  it  were  a lock-string,  using, 
however,  a less  degree  of  force.  The  lanyard  may  be  hooked  to 
the  loop  before  the  tube  is  put  into  the  vent. 

1450.  Stobage  of  Pelsiees. — Percussion  and  friction  prim- 
ers and  all  other  articles  containing  fulminating  matter  are  kept 
in  boxes  prej>ared  for  the  purpose,  and  the  boxes  are  stored, 
separately  fi-om  other  articles,  in  a dry,  secure,  and  safe  place, 
under  lock  and  key,  and  are  on  no  account  to  be  put  in  the  maga- 
zines— being  distributed  in  two  or  thi'ee  places,  and  a portion 
kept  constantly  at  hand. 

1451.  Allowance  of  Peimees. — The  allowance  of  percus- 
sion-primers to  ships  fitting  for  sea  is  three  hundred  for  each 
one  hundred  rounds,  and  fifty  per  cent,  additional  for  practice- 
in  pulhng  the  lock-string. 

84 


grinding  pai 
Friction- 


630 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  allowance  of  friction-primers  is  fifty  to  each  gnn  on 
hoard  ship. 

1452.  Spue-tubes. — These  are  quill  priming-tubes  (Fig.  319) 
filled  with  inflammable  composition,  and  ignited  by  applying 
the  match. 

The  body  of  the  tube  is  filled 
with  a composition  of  mealed-pow- 
der  moistened  with  camphorated 
alcohol  until  a thick  paste  is  formed ; 
the  composition  is  introduced  into  the 
qnill  by  pressing  its  lower  end  into 
the  paste,  thus  taking  up  a portion 
of  it,  and  repeating  the  operation 
xmtil  the  quill  is  filled. 

A small  wire  is  then  run  through 
the  axis  of  the  tube,  and  allowed  to 
remain  there  until  the  paste  is  dry  ; 
when  it  is  withdrawn,  leaving  the 
composition  perforated  throughout 
its  entire  length.  Tlie  object  of 
piercing  the  composition  is  to  ex- 
pose more  surface  to  the  action  of 
the  flame  ; the  ignition  of  the  whole 
contents  of  the  quill  is  thus  rendered 
instantaneous. 

1453.  The  head  of  the  tube,  or  is  formed  by  insert- 
ing a strand  of  quick-match,  about  an  inch  long,  into  the  com- 
position, through  a hole  near  the  head  of  the  quill.  This  is 
protected  by  a small  tube  of  stiff  paper  lashed  at  right  angles  to 
the  quill. 

The  end  of  the  quick -match  is  covered  with  a paper  cap. 

The  whole  is  shellaced  over  to  protect  it  from  moisture. 

Spur-tubes  are  packed  in  tin  boxes  in  the  same  manner  as 
percussion-primers. 

When  spur-tubes  are  used  the  Gun  Captain  exposes  the 
priming,  and  the  2d  Captain  applies  the  match. 

1454.  Slow-match  is  used  to  preserve  fire.  It  may  be  made 
of  hemp,  flax,  or  cotton  rope.  The  rope  is  saturated  with  the 
acetate  of  lead  or  the  lye  of  wood  ashes  ; if  it  is  made  of  cotton 
it  is  only  necessary  that  the  strand  be  well  twisted.  It  burus 
from  four  to  five  inches  in  an  hour,  forming  a hard-pointed 
coal,  which  readily  communicates  fire  to  any  inflammable  ma- 
terial with  Avhich  it  comes  in  contact. 

For  the  Navy,  loosely  laid,  one-inch  flax-rope  is  used. . It  is 
placed  in  a solution  of  one  pound  of  acetate  of  lead  to  five  gal- 


Fig.  319. 


PEIMERS. 


531 


Ions  of  water,  for  twenty-foiir  hours';  then  taken  ont,  rove 
through  blocks  and  well  stretched.  It  is  left  on  a stretch  for 
eight  or  ten  hours,  and  rubbed  down  smooth  with  rags ; when 
it  is  cut  in  lengths  of  about  two  fathoms  each,  and  packed  in 
boxes  ready  for  issue.  For  service  a piece  of  this  rope  two  or 
three  feet  long  is  wound  around  a match-staffs  having  a slit  in 
one  end  and  a point  of  iron  on  the  other,  which  can  be  stuck  in 
a match-tub. 

1155.  Quick-match  is  used  to  communicate  fire.  It  is 
made  of  cotton-yarn  (lamp-wick)  saturated  in  alcohol  and  then 
put  into  a composition  formed  of  mealed-powder  and  gummed 
spirits ; after  saturation  the  yarn  is  Avound  on  a reel  or  hung  up 
until  perfectly  dry. 

The  burning  of  quick-match  is  A'ery  irregular,  varying  Avith 
the  condition  of  the  match  and  the  quantity  of  powder  over  its 
surface.  One  yard  in  thirteen  seconds  is  about  the  mean  rate 
of  burning  of  new  match  Avhen  not  confined.  The  rate  of 
burning  may  be  much  increased  or  rendered  almost  instantane- 
ous by  enclosing  it  in  a tube  of  any  description. 

The  ignition  of  any  combustible  AAdiich  it  is  not  safe  to  ap- 
proach may  be  readily  effected  by  enclosing  quick-match  in  a 
paper  case  or  leader  of  the  required  length. 

115G.  PoRT-FiEE. — Fort-fire  is  a cylindrical  paper  case  con- 
taining a composition  which  burns  with  an  intense  flame.  It  is 
used  for  firing  guns  in  the  absence  of  other  means,  and  also  em- 
ployed, as  its  name  implies,  to  carry  jire  Avhenever  required. 
In  order  to  stop  the  combustion  in  a port-fire  it  is  best  to  cut  it 
off  as  near  as  possible  to  the  flame.  Port-fire  is  used  for  life- 
Ijiioy  lights,  because  of  its  ability  to  resist  Avater.  The  poAver  of 
a burning  composition  to  resist  the  penetration  of  Avater  to  the 
mass  is  in  direct  proportion  to  the  A'olume  of  gas  evoh'ed  and 
to  the  rapidity  of  its  escape,  and  consequently  to  the  rapidity 
with  AA'hich  it  burns.  Port-fire  cut  up  into  small  pieces  and 
placed  in  a shell  forms  a very  good  incendiary  material. 

1157.  In  an  emergency  Avheu  port-fire  cannot  be  procured, 
a substitute  may  be  made  by  impi-egnating  paper  with  a solu- 
tion of  12  oz.  of  saltpetre  to  1 gallon  of  Avater.  When  dried, 
the  paper  is  rolled  up  into  a solid  cylinder  about  the  size  of  the 
ordinary  port-fire.  It  burns  sloAvly,  or  rather  smoulders. 

The  finished  port-fires  are  18  inches  long  and  ^ inch  in 
diameter. 

The  composition  is  composed  of : nitre,  4 lbs. ; sulphur,  1 lb. 
10  oz. ; mealed-poAA'der,  12  oz. ; and  burns  at  the  rate  of  about 
one  inch  in  a minute. 

The  bottom  of  the  case  is  filled  Avith  clay  and  the  top  Avith 


532 


KAVAL  OEDNAXCE  AND  GTJXXERY. 


inealed-powder.  Tlie  case  is  painted  black  and  the  top  tipped 
with  red,  to  show  wliicli  end  to  light. 

When  dry,  the  port-fires  are  packed  in  laboratoiw  boxes,  50 
or  100  in  a box. 

1158.  FinrxG  Cannon  by  ELBCTEicrrr. — Many  methods  have 
been  proposed  with  this  object  in  view.  Such,  for  example,  as 
if  in  the  percussion-primer  (Art.  1139)  there  was  substituted 
for  the  fiat-head  an  arrangement  for  electrical  ignition  con- 
structed in  the  manner  descilbed  under  the  head  of  Electric 
Fuzes  (Art.  1509).  Several  contrivances  on  this  principle  have 
been  brought  forward,  but  experiment  has  not  decided  upon  the 
best.  A satisfactory  mode  of  discharging  cannon  by  electricity 
would  be  very  serviceable  in  simultaneous  and  concentrated 
firing.  Firing  salutes  by  electricity  may  be  veiy  simply  and 
easily  performeJ  by  placing  an  electric  fuze  in  each  cartridge 
and  leading  the  wires  out  of  the  muzzle  of  the  gun  to  their  a}> 
propriate  connections. 

1159.  Electric  Prijier. — The  electric  primer  chiefly  used 
consists  of  a cpfill  tube  filled  with  fine-grained  powder  or  pierced 
composition,  to  the  top  of  which  is  secured  a small  hard-wooil 
plug,  in  which  is  placed  a small  quantity  of  priming  composi- 
tion, and  the  copper  wires  so  arranged  as  to  ignite  the  compo- 
sition upon  the  passage  of  the  electrical  current,  by  which  means 
the  jiowder  in  the  tube  is  fired. 

The  head  of  the  primer  is  arranged  with  pi’oper  connections 
for  attaching  the  ends  of  the  circuit-wires  leading  from  the  bat- 
tery or  electrical  machine. 

Tliese  primers  are  useful  in  firing  time-guns,  and  also  those 
subject  to  extreme  proof. 


Section  III. — Fuzes. 

1160.  Fezes  are  the  means  used  to  ignite  the  bursting- 
charges  of  hollow  projectiles  at  any  desired  moment  of  their 
flight. 

There  are  a great  many  varieties  of  fuzes.  They  may  be 
classed  according  to  their  mode  of  operation,  percussion,  con- 
cussion, and  time  fuzes. 

1161.  The  Time-fuze  consists  of  a column  of  inflammable 
composition  which,  being  ignited  by  the  charge  in  the  gun. 
burns  for  a certain  space  of  time,  at  the  end  of  which  it  com- 
municates its  flame  to  the  bursting-charge  in  the  shell.  In  the 
Navy,  all  spherical  shells  except  those  for  howitzers  and  for 
shrapnel  are  fitted  with  the  Navy  Time-fuze. 


FUZES. 


533 


1462.  Bequirements. — The  conditions  required  to  consti- 
tute a good  time-fuze  are,  that  it  should  ignite  with  certainty  ; 
that  it  should  burn  regularly,  and  that  when  ignited  it  should 
not  be  liable  to  extinction. 

Time-fuzes  haye  the  adyantage  of  being  independent  of  the 
object,  and  of  furnishing  a core  of  dispersion  whose  aj)ex  is 
aboye  the  target. 

But  they  are  entirely  dependent  upon  the  exactness  of  their 
adjustment,  and  eyen  when  properly  adjusted  they  somethnes 
giye  premature  or  tardy  explosions  without  assigned  reasons ; be- 
sides, they  atford  no  means  of  estimating 
at  sight  the  distance  at  which  the  pro- 
jectiles hurst,  and  consequently  no  cri- 
terion for  correcting  them,  which  is  a 
great  disadyantage. 

1463.  The  Jfxyy  Time-fcze  (Fig. 

320). — This  fuze  is  composed  of  a 
composition  driyen  in  paper  case 
and  then  inserted  in  a mBcil  stocTc, 
which  screws  into  the  fuze-hole  ; so  that 
one  end  of  the  composition  lies  eyen 
Avith  the  exterior  smdace  of  the  shell, 
and  is  exposed  to  the  flame  of  the  charge 
in  the  gun,  the  other  end  being  Avithin, 
amidst  the  charge  of  the  shell.  The 
composition  is  coyered  with  a safety- 
cap,  Avhich  protects  it  from  moistime  and 
accidental  ignition ; also  with  a xoater- 
cap  of  peculiar  construction,  intended 
to  protect  the  flame  from  being  extin- 
guished on  ricochet. 

1404.  A Safety-plug  at  the  loAxer 
exti’emity  preA'ents  the  communication 
of  Are  to  the  jDowder  in  the  shell,  in  the 
eyent  of  the  accidental  ignition  of  the 
fuze  after  being  uncapped. 

1405.  Composition. — The  ingredi- 
ents of  all  thu  e-fuze  compositions  are 
the  same  as  for  gimpoAyder,  but  the 
proportions  are  A'aried  to  suit  the  re- 
quired rate  of  burning.  Pure  mealed- 
poAvder  giAms  the  quickest  composition, 
and  the  others  are  derived  from  it  by 
the  addition  of  nitre  and  sidphur  in  cer- 
tain quantities.  The  rate  of 


Fig.  320. — Xavy  Time- 
fuze. 


bm-ning 


of  a fuze  composition 


534 


NAVAL  ORDNANCE  AND  GUNNERY. 


depends  on  tlie  purity  and  tliorongh  incorporation  of  the 
materials,  and  on  its  density. 

These  qualities  are  best  secured  by  procuring  tbe  materials 
from  the  powder-mills  ready  mixed  and  gi-anulated  like  powder, 
in  which  form  it  is  not  more  liable  to  deteriorate  than  gunpow- 
der, and  can  be  preserved  for  a long  time  without  the  possibility 
of  alteration. 

The  three  compositions  used  are  manufactured  at  Dupont's 
Powder-mills,  and  are  known  by  the  letters  Z,  JZ,  and  JV. 

These  compositions  have  the  appearance  of  ordinary  un- 
glazed cannon-powder,  but  tlie  proportions  of  tbe  ingredients 
tliffer  from  those  composing  cannon-powder.  By  combining 
these  compositions  in  different  proportions  and  adding  small 
quantities  of  mealed-powder,  driving  a few  fuzes  and  burning 
them  for  trial,  the  several  compositions 
for  driving  the  various  fuzes  are  found. 

1466.  The  Paper  Fuze-case. — The 
case  into  which  composition  is  driven 
is  made  of  strong  white  paper,  which  is 
cut  into  slips  leaving  one  end  square,  the  other  tapered  to  a 
point  (Fig.  321). 

These  pieces  of  paper  are  placed  on  a smooth  board  and 
covered  Avith  a refined  glue,  used  rather  thin  and  kept  warm  in 
a suitable  vessel.  They  are  then  rolled  on  a steel  cylindrical 
former.,  beginning  Avith  the  square  end,  the  gradual  diminu- 
tion of  the  other  end  of  the  paper  producing  the  required  taper 
on  the  exterior  of  the  case.  If  one  of  these  cases  is  cut  in  any 
part,  the  several  layers  of  paper  are  not  perceptible,  but  appear 
as  if  resolved  into  a perfectly  firm  and  homogeneous  material. 

The  finished  case  (Fig.  323)  is  put  in  a gauge  to  see  that  it 
is  of  the  proper  dimensions  and  both  of  its  ends  cut  off  even 
with  the  faces  of  the  gauge. 

1467.  The  Safety-plugs  are  made  of  the  softest  lead  wire. 
This  wire  is  cut  into  short  lengths  and  put  through  molds  to 
bring  them  to  the  proper  diameter.  They  are  then  put  into 
the  plug-making  machine,  which  cuts  and  forms  the  lead  wire 
into  the  proper  shape  and  length  for  safety -plugs. 

1468.  Before  the  composition  is  driven  into  the  case,  the 
safety-plug,  P (Fig.  322),  is  inserted  with  its  cavity  end  in  the 
smaller  end  of  the  paper  case,  and  the  solid  portion  of  it  pro- 
jecting beloAv  the  tapering  end  of  the  case.  A steel  punch  with 
a conical-shaped  end,  being  introduced  into  the  case  and  enter- 
ing the  cav^ity  of  the  safety-plug,  is  struck  a smart  blow  with 
a mallet,  which  forces  the  soft  lead  out,  pressing  it  hard  against 
the  sides  of  the  paper  case. 


Fig.  321. 


FUZES. 


535 


1469.  Tlie  jar  of  concnssion  consequent  upon  the  explosion 
of  the  charge  in  the  bore  is  so  great  as  to  detach  the  plug  from 


Fig.  323. 


the  case,, so  that  from  the  moment  the  shell  leaves  the  gun  the 
communication  is  open  between  the  burning  composition  in  the 
fuze  and  tlie  bursting- 
charge  in  the  shell,  and 
as  soon  as  the  composi- 
tion is  consumed  the 
shell  will  explode. 

1470.  Fuze-driving  Fig.  323. 

Machine.— is  done 

bj  a macliine.  It  is  a screw-press  requiring  two  persons  to  work 
it.  The  driving-shaft  moves  vertically  through  a metal  tube  on 
the  exterior  of  which  is  a strong  square  thread.  A nut  works 
upon  this  by  means  of  a large  disk  attached  to  it,  of  sufficient 
diameter  to  create  the  requisite  power,  and  npon  the  upper  side 
of  this  disk  are  established  two  levers,  attached  to  the  head  of 
the  shaft.  By  adjusting  the  weights  upon  the  levers  a bell  is 
rung,  when  a pressure  of  2,000  pounds  is  obtained  with  the 
screw. 


536 


NAVAL  OKDNANCE  AND  GUNNEEY. 


1471.  The  paper  case  is  secured  in  a steel  mold  or  socket, 
which  is  made  to  adjust  so  closely  to  the  exterior  of  the  case 
as  to  sustain  it  and  also  protect  the  safety-plug  against  the 
pressure  applied  in  condensing  the  composition.  Two  or  more 
of  these  molds  are  placed  around  the  edge  of  the  cu’cular  plate 
carried  upon  the  lower  part  of  the  frame,  and  revolving  so  as 
to  bring  the  molds  in  turn  to  the  shaft. 

1472.  Driving  the  Composition. — The  composition,  being 
first  pulverized  to  a fine  powder,  is  put  into  the  case  by  a small 
scoop  which  holds  eight  or  ten  grains.  Each  charge  is  driven 
by  a steel  drift  which  fits  snugly  into  the  case,  the  workman 
moving  aroxiud  the  lower  plate  so  as  to  bring  the  didft  under 
the  driving-shaft  of  the  machine,  the  positions  being  determined 
by  a spring  and  catch  wmrking  into  a notch  in  the  edge  of  the 
plate.  The  disk  is  now  given  a cpiick  whirl  by  means  of  the 
handles  on  its  periphery,  and  the  dri\dng-shaft  descends  on  the 
drift ; the  movement  is  sustained  and  the  pressure  increased 
until  the  sound  of  the  bell  indicates  that  the  lever  has  risen  and 
the  action  of  the  machine  has  ceased. 

1473.  The  motion  of  the  disk  is  now  reversed  and  the  shaft 
sufficiently  raised  to  allow  the  woi’kman  to  revolve  the  lower 
plate  and  biiug  in  place  another  mold,  which  has  meanwhile 
been  charged.  The  operation  proceeds  until  the  column  of 
condensed  composition  is  rather  larger  than  required. 

In  this  way  the  composition  is  solidified  until  its  density  is 
doubled  and  it  becomes  as  hard  as  stone.  The  paper  cases  ai-e 
removed  from  the  driving-mold  and  placed  in  another  of  the 
exact  length  required ; the  projecting  portion  is  then  cut  oif 
evenly  wdth  a sharp  knife. 

1474.  The  Water-caj)  is  made  of  copper,  and  is  cylindrical  in 
shape  (C,  Fig.  322).  The  upper  end  has  a recess  .10  inch 
deep,  in  which  there  are  three  holes,  one  going  down  to  the 
centre  of  the  cap  and  connecting  with  the  side-holes  ; the  other 
two  are  made  to  hold  a small  piece  of  quick-match.  There  are 
two  holes  in  the  sides  of  the  cap  opposite  to  each  other  and 
connecting,  but  leading  at  different  angles;  and  one  hole  lead- 
ing from  the  bottom  of  the  cap  to  those  through  the  sides. 
Thus  the  water-cap  is  perforated  with  a channel,  Avhich  is  filled 
with  mealed  powder.  This  communicates  fire  to  the  composi- 
tion in  the  paper  case,  and  the  angles  of  the  channel  prevent 
the  enti-ance  of  any  matter,  such  as  sand  or  water,  over  which 
the  shell  may  ricochet. 

The  recess  on  top  lias  two  small  pieces  of  quick-match,  each 
secured  in  its  own  hole,  and  a small  cpiantity  of  powder  poured 
into  the  recess  and  pressed  down,  so  that  the  outer  surface  is 


FUZES. 


637 


primed  with  mealed-powder  and  strands  of  qnick-match,  which 
are  ignited  by  the  scorching  flame  that  rushes  ovmr  the  projec- 
tile at  the  tiring  of  the  charge  in  the  gun. 

1475.  The  Safety-cap  is  a circular  leaden  patch  with  a lip 
or  lug  attached  (S,  Fig.  322),  cut  out  of  soft  sheet-lead  that  is 
about  .06  inch  thick.  It  is  punched  out  with  a cutter  of  the 
proper  shape  and  dimensions. 

This  patch,  with  a thin  piece  of  parchment  of  the  same 
shape  and  size  under  it,  is  put  on  over  the  top  of  the  water- 
cap  and  driven  down  into  the  recess  in  the  head  of  the  fuze- 
stock  with  a punch  made  for  the  purpose,  having  the  length  of 
the  fuze  in  raised  letters  on  the  end,  so  as  to  leave  this  mark  on 
the  leaden  j>atch. 

1476.  The  Fuze-stoclx.  is  made  of  tough  bronze,  with  a stout 
shoulder  or  flange  at  the  outer  end  (F,  Fig.  322).  Its  length 
over  all  is  2.44  inches.  The  filled  paper  case,  or  fuze  proper,  is 
placed  in  the  metal  stock,  safety-plug-end  first,  and  then 
pressed  down  until  the  end  of  the  paper  case  is  nearly  even  with 
the  lower  end  of  the  stock,  the  safety-plug  projecting  below 
the  stock.  The  water-cap  is  screwed  in  on  top  of  the  fuze  and 
covered  with  the  safety-patch.  A circular  label  is  pasted  on 
over  the  patch  showing  the  length  of  the  fuze,  the  date  of  fab- 
rication, and  tlie  initials  of  the  inspector. 

A little  shellac  is  brushed  around  the  safety-plug  and  lower 
end  of  fuze-stock ; also  around  the  leaden  patch  and  top  of 
stock.  A pasteboard  cap  is  put  on  over  the  safety-plug-end 
of  the  fuze-stock  to  prevent  the  i)lug  from  being  broken  off, 
and  the  fuzes  thus  prepared  are  stowed  in  boxes. 

1477.  Time  of  Buknixg. — The  Navy  Tlme-fazes  are  of  3-|, 
5,  7,  10,  15,  and  20  seconds  time  of  burning ; which  times  are 
supposed  to  offer  a sufficient  variety  for  most  of  the  exigencies 
of  the  service,  and  a certain  proportion  of  each  are  supplied  to 
each  ship. 

There  are  also  supplied  for  special  purposes  paper-case 
fuzes  of  greater  length,  which  when  used  are  always  to  be  in- 
serted in  metal  stocks. 

Gexeral  Working-fuze. — All  loaded  spherical  shell  sup- 
plied are  fitted  with  the  five-seconds  fuze,  which  is  to  be 
regarded  as  the  general  working-fuze.  This  fuze  may  be  drawn 
and  any  of  the  others  substituted.  The  XV-iiich  shell  are  fitted 
with  three  fuzes,  each  3^,  5,  and  7 seconds. 

One-half  of  the  shell  allowed  for  rifled  guns  are  fitted  with 
time-fuzes,  and  the  remainder  with  percussion-fuzes. 

1478.  To  Shorten  Fuzes. — For  special  firing  any 'time- 
fuzes  may  be  shortened.  To  do  this,  unscrew  the  water-cap 


538 


NAVAL  ORDNANCE  AND  GUNNERY. 


and  back  the  paper  case  out  from  the  lower  end  with  a diift 
and  mallet,  cut  off  from  the  lower  end  with  a line  saw,  oi’  shai-p 
knife  struck  with  a mallet,  the  proportional  part  recpiired,  and 
insert  the  upper  part  in  the  stock,  forcing  it  down  with  a few 
gentle  blows  with  the  drift ; screw  in  the  water-cap. 

It  is  preferable,  however,  when  circumstances  will  admit, 
to  take  up  such  distance  as  will  correspond  with  the  time  of 
flight  of  one  of  the  regulation  lengths.  In  shortening  the 
fuzes  there  is  danger  of  disturbing  the  cohimn  of  composition. 

1179.  Testing  Fuzes. — Fuzes  are  tested  by  securing  them 
in  some  convenient  place,  lighting  them,  and  noting  the  time 
of  burning.  In  testing  the  ISTav}’-  time-fuze,  the  safety -plug 
must  be  removed.  Being  intended  for  use  under  a water-cap, 
they  burn  a longer  time  in  the  open  air.  Under  the  water-cap 
the  gases  are  so  confined  that  the  combustion  is  augmented. 

1180.  Time-fuzes  foe  Rifle-pkojectiles.- — Time-fuzes  are 
very  unreliable  in  rifle-guns  in  consequence  of  the  flame  being 
cut  otf  from  the  fuze ; with  the  Parrott  shell,  however,  the 
Navy  time-fuze  is  the  most  certain  of  ignition  and  regular  in  its 
time  of  burning. 

For  rifle-projectiles,  where  the  flame  of  the  charge  is 
entirely  cut  off  from  the  fuze,  the  time-fuzes  are  fitted  with  a 
detonating  arrangement  at  the  top.  This  consists  of  a small 
hollow  cylinder  of  metal,  termed  the  detonator^  containing  a 
small  quantity  of  detonating  composition,  and  having  a flre-hole 
communicating  with  the  fuze-composition.  K 2?lunger  \?>  sus- 
pended in  the  detonator  by  means  of  a wire,  and  when  the  gim 
is  fired  the  suspen ding-wire  is  broken,  and  the  plunger  coming 
in  contact  with  the  detonating  composition  e.xplodes  it,  thus 
firing  the  fuze-composition. 

1181.  Imperfection  of  Time-fuzes. — It  is  impossible  that 
any  species  of  fuze  should  be  absolutely  perfect.  AVhen  suita- 
ble opportunities  for  observation  occur,  it  is  noticed  that  in 
firing  a number  of  shells  many  do  not  explode.  The  failure  of 
the  composition  to  ignite  is  probably  generally  due  to  the  ab- 
sorption of  moisture  ; and  therefore  all  fuzes  taken  from  shell 
or  returned  from  ships,  which  have  been  more  than  one  year  in 
service,  are  to  be  returned  to  the  Laboratory  in  the  Ordnance 
Yard  at  AVashington,  where  all  fuzes  are  prepared.  Fuzes  of 
over  two  years’  date  of  manufacture  are  not  to  be  issued  for 
service. 

Sometimes  the  fuze  is  extinguished  after  having  been 
ignited.  This  may  occur  Avhen  the  shell  ricochets  on  soil  or 
water'.  AVater  is  not  so  detrimental  as  sand,  and  the  fuze  is 
rarely  extinguished  by  several  ricochets  upon  it. 


FUZES. 


539 


Generally  tlie  gases  evolved  by  tlie  combustion  of  the  eom- 
j)osition  will  repel  with  great  energj’  any  obtrusive  matter 
which  would  extinguish  the  fuze  if  once  in  contact  with  the 
ignited  surface. 

1482.  Peematcre  Explosion.— This  may  be  caused  by  the 
increase  of  the  ignited  surface  of  the  composition  resulting 
from  cracks  in  the  case  or  composition  itself,  or  by  interstices 
between  the  case  and  com]3osition ; and  in  proportion  to  the 
extent  of  this  cause  so  will  be  the  increased  celerity  of  the 
combustion.  Crevices  may  occur  in  the  composition  from 
some  defect  in  the  tools  or  in  the  mode  of  using  them,  or  they 
may  be  created  by  bending  the  case. 

It  may  also  happen  that  the  displacement  of  the  shell  by 
the  charge  of  the  gun  will  force  in  the  column  of  composition 
or  the  case  with  it.  This  would  of  course  cause  the  shell  to 
explode  ^•ery  quickly. 

The  shell  may  be  defective  in  thickness  or  quality  of  metal, 
and  be  crushed  by  the  force  of  the  discharge,  when  the  explo- 
sion will  take  place  in  or  near  the  gun. 

The  bursting  of  shell  near  the  muzzle  of  the  gun  is  some- 
times attributed  to  the  detonating  qualities  of  the  powder  in 
tlie  shell.  It  is  manifest  that  the  premature  explosion  of  shells 
is  far  more  detrimental  to  their  efficiency  than  the  failure  to 
explode  at  all. 

1483.  Commanders  of  vessels  are  required  to  observe  care- 
fully the  action  and  result  of  all  fuzes,  and  report  in  detail  to 
the  Bureau  of  Ordnance  whenever  opportunities  may  occur, 
particidarly  specifying  the  number  and  kind  fired,  elevation  of 
gun,  failure  to  explode,  and  satisfactory  action ; also  whether 
the  fire  was  ricochet  or  direct. 

1484.  The  question  of  a good  fuze  for  all  conditions  of 
service  is  still  to  be  determined.  For  ordinary  firing  with 
smooth-bore  projectiles,  the  service  time-fuze,  as  made  for  many 
years  past,  continues  to  give  good  results,  but  the  greatly  in- 
creased range  and  time  of  flight  at  present  obtainable  with 
heavy  guns  render  it  desirable  to  adopt  a principle  of  shell- 
explosions  independent  of  the  time  of  flight  and  of  the  preser- 
vation in  good  order  of  a long  column  of  composition. 

1485.  The  Boemanh  Fuze  was  invented  by  Captain  Bor- 
mann  of  the  Belgian  army. 

The  case  is  a metallic  disk  about  1.6  inches  in  diameter 
and  half  an  inch  thick  (Fig.  324),  made  of  lead,  hardened  suffi- 
ciently for  the  pui'pose  by  the  infusion  of  some  tin.  It  is  cast 
without  the  thread  by  which  it  is  to  be  screwed  into  the'fuze- 
hole,  and  this  is  afterwards  cut  in  an  ordinary  slide-lathe. 


540 


NAVAL  OKDNANCE  AND  GUNNEEY. 


The  metallic  fuze  is  screwed  in  flush  with  the  shell,  and 
well  luted  around  the  edge  on  the  exterior  surface. 

The  composition  is  firmly  con- 
densed into  an  interior  canal,  or 
horseshoe-shaped  indentation,  east 
in  the  disk  around  its  periphery 
and  as  near  to  it  as  possible,  open- 
ing below,  a strand  of  quick-match 
being  first  placed  in  the  bottom  of 
the  channel.  The  canal  is  closed, 
after  the  composition  is  driven,  by  a 
piece  of  the  same  metal,  correspond- 
ing in  shape  (Fig.  325).  the  cross- 
section  of  it  being  wedge-shaped. 
This  is  pressed  down  upon  the 
composition  by  a machine  sealing 
it  hermetically. 

1486.  The  upper  surface  of  the 
disk  above  the  composition  is  very 
thin,  so  as  to  yield  readily  to  the 
cutting-tool  employed  to  open  it,  its  whole  external  correspond- 
ing of  course  with  the  composition  below.  It  is  graduated  into 
seconds  and  fourths  of  seconds.  The 
end  of  the  composition  where  the  enu- 
meration begins  communicates  with  a 
small  magazine  at  the  centre  of  the  disk, 
which  is  charged  with  grained  powder, 
and  closed  on  the  inner  side  with  a 
very  tliin  disk  of  sheet-lead  so  as  to 
yield  in  that  direction  to  the  explosion. 
A pin-liole  is  sometimes  punched  in 
this  disk  to  insure  the  escape  of  the  flame 
into  the  shell. 

1487.  The  Operation  of  the  Fuze 
occurs  thus : 

The  thin  covering  of  metal  above 
the  composition  is  cut  so  as  to  lay  bare 
the  upper  surface  of  the  composition,  and  to  afford  the  flame 
access  to  it  at  the  part  desired.  The  cut  should  be  made  with 
the'  fuze-cutter  close  to  the  right  of  the  mark  in  the  index- 
plrfe  ; and  it  is  best  made  in  two  or  three  efforts  instead  of  try- 
in^to  effect  the  cut  at  once. 

Under  lire,  the  Bormann  fuze,  though  perfectly  simple,  is 
very  liable  not  to  be  cut  to  the  desired  time ; it  is  often  done 
incorrectly,  and  sometimes  not  at  all. 


Fig  324. 


TOP  VIEW 


Fig.  325. 


FUZES. 


541 


Shell  fitted  with  this  fuze  should  he  placed  in  the  gun  with 
the  cut  of  the  fuze  up,  because  in  this  position  it  is  more  cer- 
tain of  being  touched  hj 
the  flame  of  the  charge  as 
it  rushes  over  the  top  of 
the  shell. 

The  combustion  occu- 
pies the  assigned  time  in 
passing  from  the  incision 
towards  the  origin  of  the 
graduation,  when  it  trav- 
erses the  orifice  leading 
into  the  magazine,  the 
contents  of  which  ex- 
plodes smartly  towards  the 
interior,  and  then  encoun- 
ters instantly  the  charge  in  the  shell. 

1488.  The  metal  of  this  fuze  being  soft  and  its  diameter 
great,  there  is  danger  of  its  screw-thread  being  stripped,  and 
its  being  driven  in  by  the  shock  of  firing,  or  of  its  being  driven 
out  on  the  ignition  of  the  bursting-charge,  thus  afi^ording  a 
means  of  escape  for  the  gas  evolved,  without  bursting  the  shell. 
To  prevent  the  former,  a broad  shoulder,  aa  (Fig.  326),  is  left 
when  the  fuze-hole  is  tapped.  To  avmid  the  possibility  of  the  lat- 
ter, and  at  the  saane  time  to  increase  the  effect  of  a small  burst- 
ing-charge, the  fuze-hole  below  the  shoulder  is  closed  by  screwing 
in  a composition  disk,  J,  Avith  a small  hole  in  its  centre  through 
which  the  tire  from  the  fuze  is  communicated  to  the  charge. 

1489.  Advantages. — The  peculiar  excellence  of  this  fuze 
consists  in  the  driving  of  the  Avhole  mass  of  the  composition  by 
a single  pressure,  and  its  disposition  in  such  wise  that  the  com- 
bustion occurs  not  Avith  the  stratification  of  the  mass,  but  trans- 
versely to  it,  while  in  the  ordinary  fuzes  the  solidification  and 
the  process  of  combustion  are  just  the  reA^erse ; that  is,  the 
column  is  composed  of  a number  of  la^’ers  solidified  succes- 
sively liy  an  equal  pressure ; but  as  the  inferior  layers  have, 
l)esides  the  pressure  applied  to  them,  to  bear  that  of  the  super- 
incumbent layers,  it  folloAvs  that  the  mass  is  not  homogeneous, 
but  increases  in  density  with  the  inferior  position  of  the  layers. 

The  Avhole  error  of  fabrication,  whatever  it  may  be,  in  the 
JBorrnann  fuze,  is  only  experienced  when  the  fuze  is  opened 
at  its  extreme  duration.  At  all  inferior  times  it  is  reduced 
proportionally.  The  regularity  of  this  fuze  burning  is  very 
great.  The  Bormann  fuze  is  fitted  to  all  shrapnel  and  howitzer 
ammunition. 


Fig.  326. 


542 


NAVAL  ORDNANCE  AND  GUNNERY. 


1490.  Percussion  and  Concussion  Fuzes. — A percussion  or 
concussion  fuze  is  one  wliicli  is  independent  of  tlie  element  of 
time  of  fliglit,  and  wliicli  depends  wholly  upon  imjxict  for  its 
ultimate  action. 

The  distinction  between  percussion  and  concussion  fuzes 
has  been  somewhat  arbitrary,  and  the  application  of  the  terms 
has  depended  upon  the  sense  in  which  the  inventor  of  any  par- 
ticular fuze  chose  to  apply  them. 

1491.  Concussion-fuze. — A concussion -fuze  is  one  which 
is  put  in  action  by  the  discharge,  but  the  effect  of  that  action 
is  restrained  until  it  strikes  the  object. 

1492.  Requirements. — Such  a fuze,  in  order  to  be  service- 
able, must  not  only  produce  explosion  on  striking,  but  it 
must  not  produce  it  on  the  shock  of  the  explosion  of  the 
gun-charge,  nor  of  that  produced  by  the  ricochets  of  the 
projectile  in  or  out  of  the  gun.  These  fuzes  have  usually  con- 
sisted of  some  combination  of  the  highly  explosive  fulminates, 
but  the  extreme  danger  of  using  them  lias  been  a great  obsta- 
cle to  their  adoption.  Thei’e  is  no  fuze  of  this  kind  in  use  in 
the  Navy. 

1493.  The  Splingard  Fuze  is  both  a concussion  and  time 
fuze  ; the  appearance  of  the  paper  case  is  similar  to  that  of  the 

Navy  time-fuze,  but  the  internal  arrange- 
ment is  different.  The  case  is  filled  with 
fuze-composition,  and  a long  cavity  is 
formed  in  the  lower  part  of  the  composi- 
tion by  driving  it  around  a spindle  as  in  a 
rocket ; this  cavity  is  filled  Avith  moist  plas- 
ter-of-Paris,  and  a long  needle  is  inserted  in 
it,  nearly  to  the  bottom  of  the  plaster,  form- 
ing a tube  enclosed  in  and  supported  by 
the  composition.  (Fig.  327.) 

The  composition  is  ignited  in  the  usual 
way  at  the  top.  and  as  it  burns  away,  leaves 
a portion  of  the  plaster  tube  unsupported. 
'When  the  shell  strikes  its  object,  the  stock 
breaks  off  the  unsupported  ]iart  of  the  tube, 
and  the  flame  of  the  composition  immedi- 
ately communicates  with  the  bursting- 
charge  ; if  the  tube  does  not  break  the  com- 
position burns  up,  and  the  bursting-charge 
is  ignited  as  in  an  ordinary  time-fuze. 

1494.  The  Bacon  and  McIntyre  Fuze  is  A'ery  similar  to 
this,  except  that  the  internal  tube  is  differently  formed.  In 
this  fuze  a thin  copper  tube,  E (Fig.  32S),  extends  thi’ough 


Fro.  327. 


FUZES. 


643 


Fig.  328. — A,  outside  paper  case.  B,  pow, 
der  composition.  C,  inside  paper  case.  D. 
coating  of  plaster  of  Paris.  E,  conical  tube- 
F,  baU  on  tube. 


the  centre  of  tlu;  fuze-composition,  and  lias  a solid  copper  head, 
F,  secured  in  its  upper 
end  by  a little  soft  sol- 
der. The  copper  tube 
is  enveloped  with  paper, 

C,  and  between  the  pa- 
per and  the  tube  is  a 
thin  layer  of  plaster-of- 
Paris,  D. 

The  fuze  being  ig- 
nited by  the  flame  from  the  gun,  the  upper  part  of  the  com- 
position burns  away  in  the  flrst  second  or  two  of  time,  melting 
the  solder  and  leaving  the  head  of  the  tube  free  to  be  displaced 
by  the  shock  of  impact. 

Under  ordinary  circumstances  this  fuze  acts  like  the  time- 
fuze,  the  stopper,  F,  being  kept  in  place  by  the  plaster-of- 
Paris  ; but  upon  impact,  the  plaster  breaks,  the  ball  falls,  and 
the  flame  passing  through  the  tube  at  once  ignites  the  bursting- 
charge. 

1495.  — Peecussion-fxjze. — A percussion-fuze  is  one  which 
is  prepared  for  action  by  the  discharge,  and  put  in  action  by  the 
shock  on  striking  the  object.  Like  the  concussion-fuzes,  they 
have  usually  been  dangerous  from  the  fulminate  employed,  or 
from  their  complicated  and  delicate  construction. 

The  embarrassments  that  beset  the  efforts  to  realize  an 
efticient  percussion-shell  of  the  ordinary  spheri cal  , form  arise 
from  the  impossibility  of  having  the  projectile  present  a given 
point  to  the  impact,  and  no  reliable  fuze  of  this  nature  has  yet 
been  arranged  for  spherical  shells.  In  elongated  rifle-projectiles 
this  is  more  easily  accomplished,  and  there  are  on  trial  for  the 
rifled-cannon  the  percussion-fuzes  of  Schenkle,  Parrott,  and 
others. 

Perhaps  the  case  most  completely  illustrating  the  advan- 
tages that  may  accompany  the  use  of  percussion-fuzes  is  that 
of  vessels  firing  shell  at  short  and  frequently  changing  ranges. 

1496.  Requirements. — The  essential  requirements  of  a good 
percussion-fuze  are  : that  it  should  not  be  ignited  by  the  shock 
of  discharge  or  on  striking  water ; that  it  shall  be  ignited  on 
the  impact  of  the  shell  against  the  object,  and  that  it  may  not 
be  liable  to  explode  by  handling  or  during  transport. 

The  percussion-fuze  has  many  points  in  its  favor  : it  assures 
the  bursting  of  the  projectile ; it  can  be  used  for  all  ranges,  be 
they  never  so  great ; it  admits — a very  important  desideratum 
in  war — of  estimating  distances,  and  of  correcting  the  error  of 
the  estimation  ; it  augments  the  result  of  firing  by  adding  great 


544 


NAVAL  ORDNANCE  AND  GUNNERY. 


moral  to  pliysical  effect,  due  to  the  explosion  of  tlie  projectile 
in  the  midst  of  the  enemy. 

Its  only  inconvenience  is  its  inability  to  cause  the  hurstin*; 
of  the  projectile  before  it  has  touched  the  object,  thus  render- 
ing the  effects  of  fire  dependent  upon  the  nature  and  confor- 
mation of  the  target  at  the  point  of  impact. 

1497.  SciiEXKLE-FTTze. — One  of  the  simplest  forms  of  this 
kind  of  fuze  is  the  Schenkle  percussion-fuze,  vrhich  has  been 
found  very  reliable,  and  is  now  the  only  one  issued  in  the  l^avy. 

It  is  a metal  fuze-stock  (Fig.  329), 
enclosing  a movable  core-piece,  or 
steel  plunger,  bearing  a musket-cap. 
The  plunger,  primed  and  capped,  is 
confined  inside  the  stock,  in  which  it 
fits  loosely,  by  a screw  or  pin,  which 
passes  through  a hole  in  the  side  of 
the  stock  and  plunger,  to  prevent 
it  from  moving.  A safety-cap  is 
screwed  into  the  top  of  the  fuze- 
stock,  and  its  bottom  is  closed  by  a 
cork  or  leather  stopper. 

1498.  When  the  projectile  is  set 
in  motion,  the  plunger  by  its  inertia 
carries  away  the  pin  which  confines 
it,  and  pi-esses  against  the  bottom  of 
the  fuze-stock.  When  its  motion  is 
arrested,  the  inertia  of  the  plunger  causes  the  percussion- cap 
to  impinge  against  the  safety-cap,  which  ignites  the  priming, 
Avhen  the  stopper  in  the  bottom  of  the  fuze-stock  is  blown  out 
and  the  shell  exjfioded. 

1499.  As  a precaution  against  danger  while  handling,  the 
brass  safety-cap  is  countersunk  on  one  end  and  fiat  on  the 
other.  It  is  kept  with  the  countersunk  end  down  at  all  times 
except  when  loading ; Avhile  this  end  is  down,  should  the 
plunger  become  loose,  the  percussion  cap  is  prevented  from 
coming  in  contact  with  the  hard  surface  of  the  safety  cap,  but 
on  being  turned  end  for  end  a plane  surface  is  opposed  to  the 
percussion  cap,  upon  Avhich  it  may  strike.  There  is  a slit  cut 
in  the  top  of  the  fuze-stock  and  cap  which  is  designed  for  the 
entrance  of  the  fuze- wrench. 

These  fuzes  are  made  of  two  sizes,  the  smaller  size  being 
fitted  to  20  and  12  pdr.  rifle-shell,  while  the  larger  ones  are 
used  for  the  heavier  shell. 

1500.  Paeeott  Pekcussion-fttze. — This  consists  of  a metal 
fuze-stock,  A B (Fig.  330),  enclosing  a plunger,  P ; but  the  ar- 


FUZES. 


645 


rangement  is  different  from  tlie  Selienkle.  In  the  Par- 
rott fuze  the  plunger  closes 
the  bottom  of  the  stock,  and 
is  prevented  from  slij^ping 
through  by  a shoulder,  c d,  on 
the  plunger,  taking  against 
a projection  on  the  interior 
of  the  stock.  The  plunger 
is  surmounted  by  a long 
nipple,  H,  armed  vith  a per- 
cussion-cap, which  strikes 
against  a safety-cap,  S, 
screwed  into  the  top  of  the 
fuze-stock.  The  ring,  R, 
being  placed  over  the 
plunger,  its  lugs,  xx,  take 
against  the  lip,  R,  and  in 
this  position  the  cap  of  the 
fuze-stock  screws  close  down 
on  the  ring,  holding  the 
shoulder  of  the  plunger  at 
cd  firmly  against  the  projectile  on  the  inside  of  the  stock.  The 
plunger,  capped  and  primed,  is  held  firm  until  the  projectile 
strikes  the  object,  when  its  inertia  carries  away  the  lugs,  x x, 
and  the  plunger  impinges  against  the  safety -cap,  producing  the 
explosion. 

1501.  Geema:x  PEECussiOjsr-FrzE  (Tig.  331). — In  this  fuze 
the  plunger,  a h,  having  a central  fire-hole,  is  let  into  the  fuze- 
hole  and  rests  against  the  shoulders,  c c.  This  plunger  is  sur- 
mounted by  a perforated  cap,  having  a terminating  point  on 
the  top  side. 

The  plunger  is  retained  in  its  place  by  a pin,  E,  which  passes 
tranversely  into  the  fuze-hole,  the  side  of  which  is  put  in  con- 
tact with  the  point  of  the  cap. 

The  outer  end  of  the  pin  projects  on  the  side  of  the  shell, 
the  projection  being  limited  by  the  line  of  the  cylindrical  por- 
tion. The  fuze-hole  is  closed  by  a screw-cap,  f f,  having  a 
small  central  screw-hole  into  which  the  fulminate-cap,  g,  is 
screwed. 

When  fired  from  a rifle-piece,  the  centrifugal  force  generated 
by  the  revolution  of  the  shell  throws  out  the  pin,  E ; the 
plunger  by  its  inertia  is  retained  at  the  bottom  of  the  chamber 
during  the  flight  of  the  projectile ; at  the  moment  of  impact 
the  plunger  impinges  against  the  fulminate,  which,  exploding, 
ignites  the  charge  in  the  shell. 

35 


Fig.  330. — Parrott  Percussion-fuze. 


546 


NAVAL  ORDNANCE  AND  GUNNERY. 


1502.  This  is  one  of  the  simplest,  and,  at  tlie  same  time, 
most  safe  and  reliable  percussion-fuzes  jet  invented.  The  fuh 


minate-cap,  g,  and  pin,  E,  are  not  applied  to  the  shell  until  the 
instant  of  loading,  when  the  loader,  who  carries  these  articles  in 
a pouch,  screws  in  a fulminate-cap  and  inserts  the  pin,  pre- 
viously feeling  that  the  plunger  does  not  stick. 

To  keep  the  bursting-charge  in  place  in  the  shell,  a brass 
thimble,  with  a flange  about  the  top,  and  a small  hole  in  the 
bottom,  is  first  pressed  into  the  fuze-hole  and  takes  agaiust  the 
shoulder,  c.  It  is  made  a trifle  large,  and  a small  slit  on  either 
side  at  the  top  gives  it  sufficient  spring  to  lit  snug  and  tight. 
A piece  of  cloth  is  pasted  over  the  tire-hole  in  the  bottom  of 
the  thimble.  In  this  thimble  the  leaden  plunger  rests. 

Failure  to  Ignite. — Percussion-fuzes  frequently  fail  if  fired 
into  a bank  of  soft  earth,  sand,  or  other  material  which  does  not 
offer  a sufficiently  sudden  resistance ; also  if  fired  at  high  eleva- 
tion, owing  to  the  fact  that  the  rifle-shells  may  not  strike  point 
foremost. 

1503.  Moktae-fuzes. — The  mortar-fuze  now  used  is  a 
paper-case  time-fuze,  similar  in  general  appearance  to  the  ordi- 
nary paper-case  fuze,  of  long  time  of  burning.  They  are  made 
up  in  packages  and  marked  with  the  kind  and  length  of  fuze. 
For  any  shorter  time  the  fuze  is  cut  with  a sharp  knife  or  line 
saw.  With  this  fuze  is  used  a wooden  fuze-plug,  having  a 
conical  opening,  which  is  reamed  out  to  lit  the  paper  case. 


FUZES. 


547 


When  the  shell  is  loaded,  and  the  fuze  cnt  to  the  required 
length,  it  is  pressed  in  the  plug  and  the  plug  firmly  set  in  the 
fuze-hole. 

Tlie  head  of  the  fuze  having  been  covered  with  tow  or 
something  to  prevent  breaking  the  composition,  the  fuze-setter 
is  placed  on  the  plug,  and  it  is  driven  with  the  mallet  until  the 
head  is  about  of  an  inch  above  the  surface  of  the  shell. 

1504.  The  old  form  of  mortar- fuze  consists  of  a conical  plug 
of  wood,  of  the  proper  size  for  the  fuze-hole  (Fig.  332).  The 
axis  of  this  plug  is  bored  out  cyliudrieally,  from  the 
large  down  to  witliin  a short  distance  of  the  small  end, 
which  is  left  solid.  At  the  large  end  a cap  is  hollowed 
out,  and  the  outside  of  the  plug  is  divdded  into  inches 
and  parts,  commencing  at  the  bottom  of  the  cap. 

Seven  inches  extreme  length,  and  each  inch  burning 
seven  seconds,  giving  a total  length  of  forty-nine 
seconds. 

The  orifice  is  filled  with  composition  pressed  hard 
and  evenly  as  possible. 

The  cup  is  filled  with  mealed  powder  and  moist- 
ened with  alcohol.  The  rate  of  burning  is  determined 
by  experiment,  and  marked  on  a water-proof  paper 
cap,  'which  is  tied  over  the  cup. 

This  is  removed  when  the  fuze  is  used.  Knowing  the  time 
of  flight,  the  fuze  is  cut  with  a saw  at  the  proper  division,  and 
firmly  set  in  the  fuze-hole  with  a fuze-setter  and  mallet. 

The  great  disadvantage  of  this  fuze  is  its  irregularity,  it  be- 
ing very  difficult  to  press  such  a large  column  of  composition 
so  that  equal  lengths  will  burn  in  equal  times. 

1505.  Running-fuzes  for  Mines  and  Blasting. — The 
running  fuzes  most  used  are  those  known  in  England  as  Bick- 
ford^ s fuze^  and  in  this  country  as  safety-fuze  and  Tofs  fuze. 
^he  common  fuze  ordinarily  used  in  blasting  with  powder  is 
of  this  kind. 

It  consists  essentially  of  a column  of  fine  gunpowder  enclosed 
in  flax,  hemp,  or  cotton,  and  made  up  with  different  coverings 
according  to  the  use  to  which  it  is  applied.  When  intended  for 
immediate  use  on  light  work  in  dry  ground,  it  is  unprotected 
by  additional  coverings.  W^hen  intended  for  use  in  wet  ground 
or  under  water,  it  is  covered  with  varnished  tape  or  gutta-percha. 

These  fuzes  cause  ignition,  by  conveying  flame  to  the  charge 
to  be  exploded.  They  are  somewhat  uncertain  in  their  rate  of 
burning,  but  average  about  one  yard  in  a minute. 

The  ordinary  varieties  must  be  kept  in  a cool,  dry  place,  and 
j)reserved  from  contact  'uuth  grease  or  oil. 


Fig.  332. 


548 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  gutta-percha-covered  varieties  are  liable  to  become  in- 
jured by  keeping,  from  the  deterioration  of  the  gutta-percha. 
Before  using,  care  must  be  taken  that  cracking  of  the  gutta- 
percha has  not  occurred.  They  should  be  able  to  resist  water 
for  twenty-four  hours. 

1506.  Quick-match  Fuze  is  made  by  enclosing  quick-match 
in  a paper  case  with  plaited  cotton  covering,  and  water-proofed. 
(Art.  1455.) 

Gun-cotton  Fuze. — Gun-cotton  thread  or  rope  bums  with 
great  rapidity  : not  less  than  thirty  feet  per  second. 

1507.  Detonati^tg-fuzes  or  Exploders. — By  a detonating- 
fuze,  or  detonator,  is  meant  one  that  causes  a detonating  explo- 
sion. The  ordinary  method  of  producing  explosion  is  by  the 
direct  apj)lication  of  flame.  By  the  detonating  method,  explo- 
sion of  the  main  charge  is  caused  by  the  concussion  exerted  by 
a small  charge  of  explosive  material  in  the  fuze.  Fulminating 
mercury  seems  to  possess  peculiar  properties  as  a detonator,  and 
practically  is  the  only  body  so  used. 

Detonating-fuzes  are  used  when  violent  shattering  explo- 
sions are  desired.  Thus  nitro-glycerine,  gun-cotton,  and  their 
preparations  are  always  fired  by  means  of  a fulminate  exploder. 
The  ignition  of  the  fulminate  may  be  accomplished  in  the  ordi- 
nary manner,  or  by  the  use  of  electricity. 

1508.  The  simplest  fulminate  exploder  is  made  by  attach- 
ing a copper  case  or  large  cap  containing  the  fulminate  to 
the  end  of  a piece  of  common  running-fuze.  If  the  fuze  fits 
the  cap  closely,  it  may  be  retained  in  place,  and  the  cap  pro- 
tected against  moisture  by  pressing  round  it  wax,  hard  soap,  or 
other  similar  substance.  If  the  fuze  is  too  small,  it  must  be 
passed  through  a plug  of  wood  or  small  cork  fitting  the  cap, 
and  the  whole  fastened  on  as  above.  Before  it  is  fastened  into 
the  cap,  the  end  of  the  fuze  must  be  spread  out  so  as  to  ensure 
contact  with  the  fulminate.  Fifteen  grains  is  the  usual  amount 
of  fulminate  placed  in  the  cap  ; it  should  be  put  in  when  wet, 
with  some  gummy  solution  or  varnish,  so  that  it  will  dry  to  a 
solid  lump  which  will  not  shake  loose. 

Even  in  exploding  powder  there  is  often  great  advantage  in 
using  detonating-fuzes.  It  is  difficult  to  prove  that  actual 
detonation  of  the  powder  is  brought  about,  but  experiment  has 
shown  that  a much  more  violent  action  can  be  obtained  by  using 
this  mode  of  firing. 

1509.  Electric  Fuzes  axd  Exploders. — Evidently  when 
ordinaiy  running-fuze  is  employed  as  the  means  of  iofuition.  but 
one  charge  or  mine  can  be  exploded  at  a time.  In  large  blast- 
ing ojperations,  and  in  military  engineering,  simultaneous  filing 


FUZES. 


549 


of  many  charges  is  constantly  required.  Again  it  is  often  de- 
sired to  e.xplode  charges  from  a distance,  as  in  torpedo  work. 

The  applications  of  electricity  to  this  purpose  have  become 
cj^uite  extensive,  and  ofi'er  many  advantages  in  the  greater 
certainty  of  their  action,  and  the  ease  with  which  they  can  be 
employed  under  circumstances  Avhero  the  ordinary  running-fuze 
would  be  useless.  Electric  fuzes  are  always  used  with  gun- 
cotton, nitro-glycerine,  and  their  preparations,  when  any  contin- 
uous or  extensive  work  is  to  be  done  with  them. 

Electric  fuzes  or  exploders  may  be  divided  into  two  classes : 
those  in  which  the  heat  is  obtained  by  the  passage  of  the  elec- 
tric spark  over  a break  in  the  circuit,  and  those  in  wliich  the 
heat  is  obtained  by  the  passage  of  the  current  over  a conductor 
of  great  resistance. 

1510.  The  first,  or  tension-fuzes,  may  be  used  with  the 
Leyden  jar,  induction-coil,  or  any  statical  electric  machine,  such 
as  Von  Ebner’s,  Smith’s,  etc.  The  forms  in  which  they  are 
made  are  numerous,  but  essentially  they  are  all  alike. 

All  that  is  necessary  for  a fuze  or  exploder  of  this  class  is, 
that  there  shall  be  a break  in  a circuit  not  greater  than  the 
spark  can  easily  be  made  to  pass  over  to  is  the  usual 
distance),  and  that  between  the  two  points  of  the  break  shall  be 
placed  some  composition  that  will  be  ignited  by  the  passage  of 
the  spark. 

Gunpowder  can  be  so  fired,  if  packed  closely  between  the 
points,  but  it  is  better  to  use  some  more  sensitive  material  as  a 
priming.  Fulminating  mercury  is  fired  by  the  spark,  and  may 
be  used  for  this  purpose,  either  pure  or  mixed  with  other 
substances,  as  in  percussion-cap  composition.  Abel’s  composi- 
tion has  been  thus  used.  It  is  composed  of  sub-sulphide  of 
copper,  64  parts  ; subphosphide  of  copper,  14  parts ; and  chlo- 
rate of  potash,  22  parts.  Other  priming  compositions  are  also 
employed. 

The  wires  of  the  fuze  must  be  firmly  held  in  a wooden 
block  or  similar  contrivance,  in  such  a manner  that  the  priming 
cannot  be  displaced,  or  the  distance  between  the  points  altered. 
Outside  the  priming-material  is  placed  fulminating  mercury, 
gunpowder,  or  other  substance,  and  the  Avdiole  properly  en- 
closed in  a wooden  or  metallic  case.  In  other  respects  the  fuze 
may  be  made  up  as  desired,  by  coating  with  water-proof  com- 
position, varnishes,  gutta-percha,  etc. 

1511.  The  principle  difficulty  connected  with  the  use  of 
statical  electricity  for  causing  explosion  is  the  high  insulation 
of  the  conducting-wires  that  is  required.  If  the  insulation  is 
hnperfect,  the  loss  is  so  great  as  to  render  the  firing  of  the  fuze 


550 


NAVAL  OKDNANCE  AND  GUNNERY. 


uncertain  or  impossible.  Some  persons  have  tiied  to  avoid 
tliis  need  of  perfect  insulation  by  the  use  of  very  sensitive 
priming-compositions.  Many  fatal  accidents  have  been  occa- 
sioned by  this  recklessness. 

1512.  The  second  class  of  electric  fuzes  or  exploders  are 
those  in  which,  by  the  passage  of  the  current,  a portion  of  the 
circuit  having  a great  resistance  becomes  sufficiently  heated  to 
ignite  some  explosive  or  inflammable  body  in  contact  with  it. 
Ifliese  fuzes  are  used  with  the  voltaic  battery  and  the  various 
magneto-electric  machines,  such  as  Farmer’s,  Gramme’s,  Wheat- 
stone’s, Beardslee’s,  etc. 

For  convenience,  these  may  be  divided  into  two  divisions  : 
those  in  which  plnmbago,  copper  sulphide,  Abel’s  composition, 
or  other  similar  highly  resisting  substance  forms  the  part  of  the 
circuit  which  is  to  be  heated,  and  those  in  which  a fine  platinum 
wire  or  other  comparatively  good  conductor  occupies  that 
position. 

1513.  Of  the  first  division  are  the  fuzes  made  for  Wheat- 
stone’s, Beardslee’s,  or  other  similar  machines.  They  consist 
essentially  of  a break  in  the  circuit  which  is  bridged  by  a layer 
of  plumbago  or  composition  which  has  a certain  condnctins:- 
power,  and  which  will  burn  when  heated.  In  contact  with  this 
is  placed  the  gunpowder,  fulminating  mercury,  or  other  sub- 
stance which  is  the  charge  of  the  fuze.  This  anangement  is 
made  up  in  any  desired  shape. 

The  difficulties  connected  with  the  use  of  these  fuzes  and  the 
machines  for  which  they  are  made  are,  that  good  insulation  of 
the  leading-wires  is  necessary,  and  that  they  are  somewhat  un- 
certain for  various  causes. 

The  current  from  these  machines  has  less  intensity  and 
greater  quantity  than  the  static,  but  is  more  intense,  and  has 
less  volume  than  the  voltaic  current,  or  that  generated  by  Far- 
mer’s or  Gramme’s  machines.  Safe  fuzes  of  this  sort  may  be 
made,  since  no  very  sensitive  composition  is  reqnired  as  a prim- 
ing. 

1514.  Of  the  second  division  are  those  known  as  platinum- 
wire  fuzes  or  German-silver-wire  fuzes.  These  are  used  with  the 
galvanic  battery  and  Farmer’s  or  Gramme’s  machines.  Several 
varieties  are  made  in  this  country  and  in  Europe.  Of  this  kind 
are  the  fuzes  made  at  the  Toiqtedo  Station,  and  issued  for  tor- 
pedo purposes,  to  be  used  with  Farmer's  dynamo-electric 
machine. 

The  essential  point  in  the  construction  of  all  the  fuzes  of  this 
division  is  the  placing  of  a short  piece  of  very  line  metallic 
(platinum  or  German  silver  is  generally  used)  wire  in  the  cir- 


FUZES. 


651 


cuit,  and  in  contact  with  it  a priming-material  which  when 
tired  ignites  the  fnze-mass,  or  the  wire  may  be  embedded  in  the 
fiize-m  iss  itself,  and  thus  inflame  it  directly,  without  the  inter- 
vention of  a priming. 

1515.  This  form  of  electric  fuze  has  many  advantages.  The 
current  with  which  it  is  used  is  one  of  great  quantity  and  low 
intensity,  so  that  the  insulation  of  the  conducting-wires  need 
not  be  as  complete  as  in  the  other  cases.  In  fact,  no  insula- 
tion is  recpiired,if  the  fuze  is  suflicieutly  delicate  and  the  whole 
circuit  is  not  too  long. 

As  long  as  the  fuze  is  whole,  the  current  is  complete,  as 
may  be  shown  by  the  passage  of  a weak  current.  It  may, 
therefore,  be  tested  at  any  time  before  using  it,  even  when  in 
the  charge  and  the  certainty  of  firing  demonstrated,  whereas 
with  the  other  kinds,  actual  trial  is  necessary. 

Gi’eater  uniformity  is  attained,  since  these  fuzes  can  be  made 
to  conform  to  any  standard  of  resis- 
tance. This  point  becomes  of  great 
importance  when  firing  takes  place  at 
great  distances,  or  when  a great  number 
of  simultaneous  explosions  are  to  be 
made.  These  fuzes  are  safe  to  handle, 
since  no  highly  sensitive  composition  is 
needed  as  a priming. 

1516.  The  Dynamo-electetc  Igniter 
now  supplied  to  the  service  (Fig.  333) 
consists  of  a hard  wooden  plug,  a,  half 
an  inch  in  length, 
inch  in  diameter, 
about  its  centre,  and 
groove  on  either  side  (the  bottoms  of 
which  are  of  an  inch  apart)  for  the 
reception  of  the  copper  wires.  There 
are  also  two  cotton-covered  (braided) 
copper  wires,  which  are  twisted  together 
for  about  an  inch,  and  are  stripped  of 
their  insulation  almost  to  the  twist ; 
these  uncovered  parts  are  pressed 
firmly  into  the  grooves  in  the  sides  of 
the  plug,  and  cut  off,  so  that  they  pro- 
ject about  one-eighth  of  an  inch  above 
the  plug ; the  ends  of  the  wires  are  now 
split  with  a very  fine  saw,  in  the  direc- 
tion of  the  plane  passing  through  them,  and  the  distance  be- 
tween the  ends  carefully  adjusted  to  IT  of  an  inch,  after  which 


05  ’ „ 

and  about  of  an 
having  a score  cut 
longitudinal 
bottoms 


a 


Fig.  333. 


552 


NAVAL  ORDNANCE  AND  GUNNERY. 


sinking  it  about  an  eighth  of  an  inch, 
wire  is  next  found  and  marked  upon  the 


platinum  wire  No.  40  is  stretched  between  them,  to  form  the 
bridge,  and  securely  soldered  to  the  ends  of  the  split  wires,  i i. 

A wisp  of  gun-cotton,/’,  is  next  wrapped  around  the  platinum 
wire,  and  the  ends  of  the  copper  wire  pinched  together  sufficiently 
to  take  all  strain  off  the  platinum  wire.  The  plug  is  now  in- 
serted in  a hollow  wooden  case,  &,  two  inches  long,  counter- 

The  resistance  of  the 
upon  me  case ; it  should  not 
vary  more  than  five-tenths  either  side  of  0.42  ohms.  The 
upper  part  of  the  case  is  filled  with  rifie-powder,  the  top  being 
closed  with  a disk  of  coi’k,  over  which  is  poured  some  water- 
proof composition,  and  the  whole  is  properly  coated  with 
shellac  to  render  it  water-proof. 

1517.  The  Dynawo-Electeic  Fuze  is  made  by  enclosing  one 
of  the  D.  E.  Igniters  in  a stout  paper  case  about  six  inches  in 
length,  which  is  filled  with  rifle-powder  to  give 
more  flame  and  consequently  a more  perfect  igni- 
tion of  the  charge  than  can  be  obtained  by  the  igni- 
ter alone.  (Fig.  334.) 

The  ends  of  the  ease  are  properly  closed,  a 
wooden  plug,  B,  with  grooves  cut  in  the  sides 
for  the  wires,  being  used  for  the  bottom,  and 
a disk  of  cork  for  the  top,  which  is  coated  with  col- 
lodion, and  seals  the  cork  firmly  into  the  case.  The 
fuze  is  given  two  coats  of  brown  shellac.  The  ends 
of  the  wires  below  the  plug  are  stripped  of  their 
covering  and  brightened. 


Section  lY. — Signals. 

1518.  Kixds. — The  preparations  employed  for 
signals  are ; rockets,  signal-lights,  navy  red,  white, 
and  Hue  lights. 

1519.  SiGXAL-EocKETS. — A signal-i’ocket  is  a 
cylindrical  case  of  paper  or  metal,  a (Fig.  335),  at- 
tached to  one  extremity  of  a light  wooden  rod,^/, 
and  containing  an  inflammable  composition,  h,  which, 
being  fired,  shoots  the  whole  of  the  arrangement 
thi’ough  the  air,  by  the  principle  that  an  unbal- 
anced reaction  from  the  heated  gases  which  issue 
from  openings  in  fireworks,  gives  them  motion  in 
the  opposite  direction.  The  principal  parts  of  a 
signal-rocket  are:  the  ease,  a\  the  composition, 


Fig.  334. 


the  head,  c : 


the  decorations,  e \ 


and  the  stick,/! 


SIGNALS. 


553 


1520.  Case. — The  case  is  made  by  rolling  stont  paper 
covered  on  one  side  with  paste  around  a former.,  and  at  the 


same  time  applying  a pressure  until  all  the  layers  adhere  to 
each  other.  The  vent  is  formed  by  choking  one  end  of  the  case 
while  wet,  and  wrapping  it  with  twine. 

The  paper  case  is  covered  outside  with  paste,  and  enclosed 
in  a cylindrical  case  of  tin,  inches  in  diameter  and  9 
inches  long.  The  lower  edges  of  the  tin  case  are  turned  under 
slightly,  to  keep  the  paper  case  from  going  through. 

1521.  Composition. — A variety  of  compositions  are  em- 
ployed for  sign  ah  rockets  ; the  best  can  only  be  determined  by 
trial,  as  it  varies  with  the  condition  of  the  ingredients. 

The  following  proportions  are  used  in  the  jSTaval  Labora- 
tory : 

bTitre 4 lbs.  8 oz. 

Sulphur 1.2  oz. 

Charcoal 2 lbs. 

IVIealed-powder 4 oz. 

To  increase  the  length  and  brilliancy  of  the  trail,  add  steel  or 
cast-iron  tilings. 

1522.  Driving. — The  case  is  placed  in  a steel  mold,  which 
has  a conical  spindle  attached  to  the  centre  of  its  base  to  form 
the  bore,  g.  This  spindle  is  made  of  composition,  6^  inches 
long,  and  goes  up  through  the  vent  into  the  centre  of  the  case, 
having  a hemispherical  bottom  to  fit  the  choke,  A. 

The  composition  is  driven  with  a screw-press  regulated  to  a 
pressui’e  of  about  5 tons.  The  first  and  second  drifts  are  made 
hollow  to  fit  over  the  spindle,  and  the  third  is  solid.  A small 
ladleful  of  pulverized  clay  is  first  put  in  and  pressed  down 
around  the  spindle,  forming  a bottom  J inch  thick.  The 
composition  is  next  put  in,  a ladleful  at  a time,  each  one 
pressed  down  separately. 

The  top  of  the  case  is  closed  with  clay,  which  is  one  diame- 
ter thick,  and  perforated  with  a small  hole  for  the  passage  of 
the  flame  from  the  burning-composition  to  the  head  ; through 
this  hole  a strand  of  quick-match  is  placed. 

The  rocket  is  primed  by  inserting  one  end  of  a strand  of 
quick-match,  eight  or  ten  inches  long,  through  the  vent  into  the 


554 


NAVAL  ORDNANCE  AND  GUNNERY. 


bore,  and  coiling  tbe  remainder  in  the  recess  formed  by  the 
choke.  A piece  of  paper  is  pasted  over  the  end 
to  protect  it. 

1523.  Head. — The  head  is  formed  by  a tin 
cylinder  inches  diameter  and  2^  inches  long, 
joined  to  a hollow  tin  cone  2-|  inches  high,  making 
the  length  of  head  5 inches.  (Fig.  336.) 

The  long  tin  case  goes  about  ^ inch  into  the 
cylindrical  part  of  the  head,  and  a piece  of  paper 
is  pasted  over  the  joint.  The  object  of  the  head 
is  to  contain  the  decorations,  which  are  scattered 
through  the  air  by  the  explosion  which  takes 
place  when  the  rocket  reaches  the  summit  of  its 
trajectory.  The  explosion  is  produced  by  a small 
charge  of  rocket-composition,  which  is  put  into 
the  head  with  the  decorations.  When  the  com- 
position is  consumed,  the  bursting-charge  explodes 
the  head  and  ignites  the  decorations,  which,  fall- 
ing, produce  a brilliant  light  that  can  be  seen  at 
a great  distance. 

1524.  Decorations. — The  decorations  of  rock- 
ets are  of  various  kinds ; those  used  in  the  navy 
are  white  stars. 

Stars. — Stars  are  fonned  by  driving  the  com- 
position moistened  Avith  alcohol  and  gum-arabic  in 
solution  in  port-lire  molds,  or  molding  it  in  brass 
cylinders  of  the  desired  diameter.  It  is  then  cut 
into  short  lengths  and  dredged  (sprinkled)  with 
mealed-powder.  The  gum-arabic  is  intended  to 
give  such  consistency  to  the  stars  that  the  explo- 
sion of  the  head  of  the  rocket  may  not  break  them  in  pieces, 
and  thereby  destroy  the  effect. 

White  Star  Composition. 


FTitre 3^  oz. 

Sulphur If  oz. 

Mealed-powder f oz. 


1525.  Sticks. — The  stick  is  a tapering  piece  of  pine,  about 
nine  times  the  length  of  the  case,  and  the  large  end  is  tied  to 
the  side  of  the  case,  to  guide  the  rocket  in  its  flight,  as  it  has 
no  rotary  motion. 

The  common  centre  of  gravity  of  the  rocket  and  stick  is  a 
little  below  the  former.  The  stick  counteracts  by  the  resist 


I 

U 

Em.  336. 


SIGISTALS. 


555 


ance  of  tlie  air  upon  it  and  tendency  to  turn  over,  and  main- 
tains the  rocket,  during  its  flight,  as  nearly  as  possible  in  the  di- 
rection in  which  it  is  hred. 

1526.  Motive-power. — The  object  of  having  the  cavity  or 
bore  in  the  interior  of  the  rocket  is,  that  a large  surface  of  com- 
position may  be  at  once  ignited  when  the  rocket  is  fired,  and  so 
great  a quantity  of  gas  generated  in  the  case  that  it  cannot  es- 
cape from  the  vent  as  quickly  as  formed,  and  therefore  exerts 
a pressure  in  every  direction  on  the  interior  surface  of  the 
rocket.  The  pressures  on  the  sides  of  the  rocket  mutually  bal- 
ance each  other,  but  the  pressure  on  the  head  is  greater  than 
that  on  the  base,  in  consecpaence  of  the  escape  of  gas  from  the 
vent ; it  is  this  excess  of  pressure  on  the  head  over  that  on  the 
base  which  causes  the  rocket  to  move  forward,  this  being  merely 
a similar  action  to  the  recoil  of  a gun. 

The  force  which  produces  motion  in  a rocket  is  therefore 
different  from  that  which  acts  upon  a projectile  fired  from  a 
piece  of  ordnance;  the  former  is  a constant  force  producing  ac- 
celerated motion  in  the  rocket  until  the  resistance  of  the  air  is 
equal  to  the  force  or  the  composition  is  consumed  ; while  the 
latter  may  be  considered  merely  as  an  impulsive  force,  which 
ceases  to  act  upon  the  projectile  when  it  has  left  the  bore  of  the 
piece. 

1527.  Packing  Pockets — The  cases  are  painted  red  and 
packed  in  laboratory-boxes,  30  to  50  in  a box.  The  sticks  are 
tied  up  in  bundles  and  packed  separately. 

1528.  Fikixg  Rockets. — A few  rockets  are  always  kept 
mounted  and  ready  for  use.  To  fire  a rocket,  the  stick  is  placed 
in  a trough  or  tube,  as  a guide ; a musket-barrel  will  answer  the 
purpose.  The  paper  covering  the  bottom  is  torn  off,  exposing 
the  priming.  Holding  the  guide  vertical  or  nearly  so,  a slow- 
match  is  applied  to  the  priming,  which  ignites  the  composition. 
The  inflamed  gas  issues  violently  from  the  bottom  of  the  case  as 
the  rocket  ascends. 

The  time  of  ascent  is  from  7 to  10  seconds,  and  they  will 
attain  a height  of  about  500  yards. 

Under  favorable  circumstances,  a signal-rocket  may  be  seen 
within  a circuit  of  from  30  to  40  miles.  In  mounting  rockets 
the  stick  is  attached  so  that  it  will  hang  end  down,  when  sup- 
ported, close  up  along  side  the  bottom  of  the  rocket. 

1529.  CosTox  SiGXAL-LiGHTS. — These  are  the  usual  night- 
signals  of  the  Havy.  They  consist  of  red,  green,  and  white 
lights,  and  their  various  combinations,  representing  the  different 
numbers  and  pendants.  The  colors  assimilate  as  far  as  possible 
with  those  of  the  day-flags. 


556 


NAVAL  ORDNANCE  AND  GUNNERY. 


1530.  The  case  is  made  of  fuze-paper  three  inches  long  and 
inches  in  diameter.  A cylindrical  block  of  soft  wood  4'  inch 
long  forms  the  bottom,  A,  with  a wooden  nipple  attached,  to  fit 
into  the  signal-holder,  or  firing-pistol.  (Fig.  337.)  Through 


Fig.  337. 

the  centre  of  the  bottom  is  a small  hole,  with  a thin  copper  tube 
inch  in  diameter,  B,  extending  through  the  middle  of  the 
case  to  withiu  ^ incli  of  the  top.  Hollow  drifts  are  used  in 
filling,  which  are  struck  15  moderate  blows  with  a half-pound 
mallet  for  each  charge.  The  ease  is  filled  to  the  top  of  the  cop- 
per tube ; the  last  charge  being  ^ ounce  of  mealed-powder. 
A small  strand  of  quick-match  is  put  through  the  copper  tube 
and  Avooden  bottom,  the  upper  end  stitched  to  the  side  of  the 
paper  case  above  the  mealed-powder,  and  the  lower  end  split  to 


Fig.  333. 


make  sure  of  its  ignition  by  the  cap  from  the  pistol.  (Fig.  338.) 
1531.  The  top  of  the  ease  is  covered  Avith  a thin  wafer  of 


SIGNALS. 


557 


brown  paper,  immediately  over  the  qnick-matcb  and  mealed- 
powder ; then  over  all  is  a pasteboard  top,  with  a rim  secured 
to  the  body  of  the  case  by  a strip  of  paper  pasted  on  both,  C. 
The  wooden  bottom  is  covered  with  shellaced  paper.  The 
signal  is  finally  covei’ed  with  white,  red,  or  green  paper,  ac- 
coi’ding  to  the  color  of  the  composition,  and  packed  in  labor- 
atory-boxes for  issue. 

The  several  colors  in  the  Coston  signals  are  intended  to  burn 
from  8 to  10  seconds. 

1532.  In  a signal  composed  of  three  colors,  1^  charges  of 
the  composition  of  the  last  color  to  be  burned  are  put  in  first 
and  driven ; a thin  circular  disk  of  paper  is  pnt  in  the  case  on 
top  of  this  composition,  then  1|-  charges  of  the  second  color  are 
put  in  and  driven,  a piece  of  paper  put  on,  and  then  1|-  charges 
of  the  first  color  to  be  burned  are  driven. 

When  a signal  is  composed  of  but  two  colors,  the  lower 
thu’d  of  the  paper  case  is  filled  with  powdered  clay,  and  driven 
the  same  as  the  composition,  then  on  top  of  this  clay  the  second 
colored  composition  is  driven,  and  on  that  the  first.  AV^hen  but 
one  color  forms  a signal,  two-thirds  of  the  case  is  first  filled 
with  clay,  and  the  composition  driven  in  the  upper  third. 

1533.  Composition  of  ^Yhite  Signals : 

5 parts  of  Sublimate  of  Sulphnr, 

5 “ “ Sulphuret  of  Antimony, 

2 “ “ Eed  Oxide  of  Lead, 

3 “ “ Sulphuret  of  Arsenic, 

^ “ “ Bleached  Shellac, 

21  “ “ ISTitrate  of  Potash. 

JCor  the  Red,  Light. 

16  parts  of  Chlorate  of  Potash, 

6 “ “ Oxalate  of  Strontium, 

2 “ “ Bleached  Shellac, 

2 “ “ Sugar  of  Lead, 

^ “ Desiccated  Lampblack. 

For  the  Green  Light. 

4 parts  of  Chlorate  of  Mercury, 

2 “ “ Bleached  Shellac, 

12  “ “ Chlorate  of  Barium. 

Bed,  White,  and  Blue  Lights  are  made  in  the  same  man- 


558 


NAVAL  OEDNANCE  AND  GUNNEET. 


iier  as  the  Coston  signals,  and  are  of  the  same  size.  They  only 
diifer  in  the  burning  composition,  which  is,  for  the 

Navy  NJdte  Light. 

Composed  of  68  parts  of  Nitre, 

18  “ “ Sulphur, 

13  “ “ Mealed-powder, 

4r^  “ “ Oi’piment, 

3^  “ “ Antimony. 

Navy  Red  Light. 

Composed  of  61  parts  of  Strontium, 

20  “ “ Shellac, 

37  “ “ Chlorate  Potash, 

3 “ “ Charcoal, 

7 “ “ Sulphate  Antimony.? 

Navy  Blue  Light. 

Composed  of  21  parts  of  Ammoniated  Copper, 

18  “ “ Oxide  of  Copper, 

12  “ “ Shellac, 

6 “ “ Oaijiment, 

68  “ “ Chlorate  of  Potash. 

1531.  Stowage  of  Ptrewoeks. — The  fireworks,  after  care- 
fully remo^dng  all  fulminating  matter,  such  as  caps  or  primers, 
if  any  such  he  used  to  ignite  them,  are  stowed  in  their  proper 
packing-boxes,  or  other  light  boxes  of  suitable  length,  made 
water-tight  and  secured  witir  lock  and  key. 

These  boxes  are  made  to  fit  between  the  beams  and  carlines 
of  the  gun-decks  of  frigates  and  berth-decks  of  single-decked 
vessels. 

Those  for  instant  use  are  placed  near  the  after-hatch,  and 
the  remainder  abaft  that  position,  if  possible,  so  as  to  be  con- 
stantly under  the  care  of  the  sentinel  at  the  cabin-door.  In  no 
case,  however,  are  they  to  be  placed  over  any  standing  light  or 
lantern  on  any  deck. 


Section  Y. — Preparing  Ammunition. 

1535.  Coviposmox. — Ammunition  is  composed  of  projec- 
tiles, cartridges,  etc. 


PEEPAKIXa  AMMUNITION. 


559 


The  cartridges  and  projectiles  used  with  heavy  ordnance  are 
fitted  and  stored  separately. 

1536.  MAKmG  Cakteldge-bags. — Cartridge-bags  are  made 
of  two  shapes : conical,  for  gomer  chambers,  and  cylindrical  for 
other  ordnance.  The  cartridge-cloth  from  which  the  bags  are 
made  is  woven  expressly  for  the  pui’pose,  being  entirely  of 
wool,  and  of  close  and  uniform  texture.  It  is  manufactured  in 
pieces  varying  in  width  from  sixteen  to  thirty-six  inches  ; the 
different  widths  being  adapted  for  the  several  lengths  of  cylin- 
ders to  save  waste  in  cutting. 

Cartridge-bags  for  cylindrical  chambers  are  made  of  a rectan- 
gle to  form  the  cylinder,  and  a circular  piece  to  form  the  bot- 
tom. The  flat  patterns,  by  which  the  cartridge-bags  for  the 
8-inch  and  32-pounder  guns  are  cut,  are  consecprently  to  be  made 
rectangular  for  the  cylindrical  part  of  the  bag,  and  circular  for 
the  bottom.  The  length  of  the  rectangle  is  ecpial  to  the  devel- 
opment of  the  cylinder,  together  with  the  allowance  for  seam ; 
and  its  width,  to  the  whole  length  of  the  bag  before  sewing, 
including  the  allowance  for  seam  and  tie.  S^recial  patterns  are 
furnished  for  those  of  XY-in.,  Xl-in.,  X in.,  IX-in.,  S-inch  of 
6,500  lbs.,  and  32-pounder  of  4,500  lbs.,  shell-guns,  all  of  which 
have  gomer  chambers. 

Cartridges  for  gomer-chambered  ordnance  are  made  conical 
in  shape,  and  out  of  two  pieces.  In  cutting,  the  length  of  the 
rectangle  should  be  taken  in  the  direction  of  the  length  of  the 
stutf,  as  it  does  not  stretch  in  that  direction,  and  the  material 
should  be  chosen,  as  nearly  as  possible,  of  the  width  rec[uired 
for  the  length  of  the  bags,  to  save  waste  in  cutting. 

The  bags  are  to  be  sewn  with  worsted  yarn,  with  not  less 
than  eight  stitches  to  the  inch ; they  must  be  stitched  within 
four-tenths  of  an  inch  of  each  edge,  and  the  two  edges  of  the 
seam  felled  down  upon  the  same  side,  to  prevent  the  powder 
from  sifting  through.  The  edges  of  the  bottom  are  felled  down 
upon  the  sides. 

The  bags  when  filled  must  be  tied  with  woollen  thrums. 

1537.  Cartridge-bags  for  Saluting-charges. — Old  cartridge- 
bags  which  have  been  condemned  for  service-charges  are  to  be 
repaired  and  used  for  saluting-charges ; and  whenever  it  is  nec- 
essary to  make  bags  expressly  for  the  purpose,  or  for  immedi- 
ate use,  they  may  be  formed  by  sewing  together  trvo  rectaugii- 
lar  pieces  with  semi-circular  ends. 

1538.  Insjyeetion. — The  material  especially  procured  for  car- 
tridge-bags is  to  be  carefully  inspected,  to  detect  any  mixture  of 
cotton  with  the  wool,  by  burning  a few  bits  taken  at  hazard 
fi’om  each  piece,  or  by  dissolving  it  in  a solution  of  half  an 


560 


NAVAL  ORDNANCE  AND  GUNNERY. 


ounce  of  caustic  potassa  in  a pint  of  water- — the  cloth  to  be  put 
in  Avhen  the  water  is  boiling,  which  is  to  continue  until  dissolu- 
tion takes  place.  The  texture  of  the  stuff  is  also  to  he  examined 
and  its  strength  tried,  such  standard  for  the  latter  being  estab- 
lished as  may  be  found  sufficient  to  ensure  perfect  efficiency. 

1539.  Preservation. — Cartridge-bags,  as  well  as  the  material 
for  making  them,  must  be  frequently  examined,  to  prevent  their 
being  damaged  by  moisture,  as  well  as  to  guard  against  moths. 
And  they  are  never  to  be  exposed  on  the  shelves  in  store,  but 
must  be  carefully  packed  by  hydraulic  press  in  linen  cloth,  or 
by  enveloping  them  in  water-proof  paper  hermetically  sealed. 

1540.  IhLLiNG  Carteh)ge-bags. — Standard  powder-measures 
for  filling  cartridges  for  great  guns  are  distributed  as  they  may 
be  required  for  the  use  of  vessels  and  shore-magazines.  As  the 
gravimetric  density  of  powder  varies  from  860  to  940,  the 
weight  of  the  contents  of  ten  measures  should  be  ascertained 
for  each  lot,  and  allowance  made  accordingly  before  filling  the 
cartridges.  In  taking  the  weights,  the  powder  is  to  be  scooped 
up  from  the  filling-chest  with  the  measure  until  it  is  heaped, 
tapped  twice  moderately  on  the  sides  Avith  the  palms  of  the 
hands,  and  then  struck  with  a wooden  straight-edge.  If  the 
weight  differs  materially  from  that  marked  on  the  measure,  a 
small  compensating-measure  should  be  used  to  supply  the  defi- 
ciency or  remove  the  excess. 

When  cartridges  are  filled  for  issue,  the  powder  should  be 
selected,  as  far  as  practicable,  from  dehveries  made  by  the  same 
person,  and  at  the  same  time  or  date. 

1541.  Marking  Cartridge  bags. — The  color  of  the  cloth  is 
white,  and  Avhen  made  up  each  bag  is  stencilled  in  black  with 
the  calibre  of  gun  and  weight  of  charge  in  figures  two  and  a 
half  inches  long,  for  all  service-charges. 

The  cylinders,  or  cartridge-bags,  in  which  the  powder  is  put 
up  for  “ saluting,”  “torpedo,”  “howitzer,”  “shell-powder,”  or 
“ shell-charges  ” are  also  to  be  distinctly  stenciUed  as  such,  in 
the  same  manner. 

1542.  Sekauce-chakges. — Tliere  are  certain  fixed  charges 
termed  serMce  charges  for  all  guns. 

The  amount  of  powder  in  tlieseiwice  charge  of  a gun  should 
be  such  that  it  will  give  the  greatest  initial  velocity  to  the  pro- 
jectile without  too  great  strain  on  the  metal  of  the  piece,  or  a 
too  violent  recoil  of  the  gun. 

The  service-charges  for  the  different  calibres  and  classes  of 
Naval  smooth-bore  guns  noAv  used  in  the  Navy  are  as  follows, 
and  the  cartridges  are  to  he  filled  accordingly,  viz. : 


PEEPAUmG  AMMUNITION. 


561 


Service  Charges  for  Naval  Guns. 


Gnxs. 

CUAUGES. 

Calibre. 

Weight. 

Battering- 
charges — 
solivl  shot. 

For  clislant 
filing, 
1-lOth. 

For  ordinary 
fir'ng, 
O-lOths. 

O . 

B 

to  w S) 

.S  ^ 

5 c ^ 

ci  ^ 

OQ 

Shape  of 
Cylinder. 

Shell  guns. 

Vos, 

lbs. 

lbs. 

lbs. 

lbs. 

XV-in 

43.000 

10.000 

100  M.  P. 

50 

35 

Conical 

Xl-in 

30,  rifle 

20 

15 

7 

X-in 

12,500 

9,000 

6.500 

4.500 

15 

13.5 

6 

IX-in  

13 

10 

7 

( ( 

Vlll-in 

7 

7 

4 

(( 

G 

6 

4 

(4 

Vlil-in 

03  cwt. 

9 

8 

4 

Cylindrical 

Vlll-in. 

55  “ 

7 

7 

4 

Shot  guns. 

X-in.,  or  130-pdr. . . 
(5 1-pflr 

16,000  Iba. 

30 

18 

6 

U 

106  cwt. 

16 

12 

4 

a 

83  

61  “ 

10 

8 

4 

n 

33  “ 

57  “ 

9 

8 

4 

ki 

33  

51  “ 

8 

7 

4 

a 

33  “ 

40  “ 

7 

7 

4 

a 

32  “ 

42 

6 

6 

4 

a 

33  “ 

33  “ 

45 

4.5 

4 

a 

33  “ 

27  “ 

4 

4 

3 

44 

Charges  for  Naval  Rifle  Guns. 


Gan. 

Calibre. 

Weight. 

Diameter 

CriARGB  OP  POWDER. 

of  bore. 

Weight. 

Kind. 

Diameter 
of  guage. 

Parrott 

100-pdr. 

Powids. 

9,700 

Inches. 

6.40 

Pounds. 

8 

Pifle 

Inches. 

5.50 

44 

GO  “ 

5,400 

5.30 

6 

44 

4.60 

44 

30  “ 

3,550 

4.30 

3.25 

Cannon 

3.70 

44 

20  “ 

1,750 

3.67 

3 

4 4 

3.25 

DaUgren 

»4 

20  “ 

1,340 

4.00 

2 

44 

12  “ 

880 

3.40 

1 

44 

Witli  the  XV-inch  guns  at  close  quarters  against  iron-clads, 
100  pounds  of  hexagonal  or  mammoth  powder  and  a solid  shot 
36 


562 


NAVAL  ORDNANCE  AND  GUNNERY. 


may  be  iissd  for  twenty  rounds  ; so  also  with  the  Xl-inch,  30 
pounds  of  rifle  and  a solid  shot. 

With  all  other  guns,  under  like  circumstances,  and  where 
penetration  is  desired,  the  distant  firing-charges  should  be  sub- 
stituted for  the  ordinary  firing. 

Saluting  charges  are  to  be  of  under-proof  powder. 

E.xperiinents  have  established  the  ability  of  our  XV-iuch 
guns  to  endure  charges  of  one  hundred  pounds  of  powder  and 
a solid  shot,  and  it  is  believed  that  they  will  stand  even  heavier 
charges. 

The  service  demanded  of  them  requiring  a wide  range  of 
charge,  the  seiwice-charge  will  vary  with  the  object  to  be 
attained. 

15T3.  Fok  Mortars. — The  bag  is  only  used  to  carry  the 
powder,  and  when  the  piece  is  loaded  the  powder  is  poured 
into  the  chamber ; bags  of  any  suitable  size  will  answer  for 
this  service. 

154T.  For  Hot-shot. — Cartridge-bags  should  be  made  doir- 
ble  by  putting  one  bag  within  another.  The  charge  ought 
not  to  exceed  three-fourths  the  service- charge,  for  in  conse- 
quence of  the  expansion  of  the  shot  the  windage  is  reduced 
and  a greater  strain  will  be  exerted  on  the  metal  of  the  gun. 
The  expansion  of  the  gas  will  also  be  increased  by  the  heat 
generated  within  the  bore  ; and,  moreover,  very  great  penetra- 
tion is  not  required,  the  object  to  be  attained  being  that  the 
shot  shall  merely  lodge  in  the  timber. 

1545.  Strappixg  Shell. — All  spherical  shell  and  shrapnel 
are  fitted  with  sdbuts. 

The  sabot  is  a thick  circular  disk  of  wood,  cut  with  the 
grain  running  plank-ways,  about  the  diameter  of  the  low  gauge 
of  the  projectile,  and  with  a cavity  or  saucer  on  one  end  to 
receive  it.  The  projectile  is  secured  to  it  with  four  straps  of 
tin.  The  straps  are  fastened  to  a ring  of  tin  encircling  the 
fuze-hole  by  cutting  four  slits  in  the  ring,  into  whicli  the  upper 
ends  of  the  straps  are  hooked,  turned  down  on  the  inside  of  the 
ring,  and  soldered.  The  lower  ends  of  the  straps  are  tacked  to 
the  side  and  under  the  bottom  of  the  sabot,  at  equal  distances 
from  each  other.  A piece  of  twine  is  passed  around  between 
the  sabot  and  projectile  to  frap  the  parts  together. 

The  Fnglish  attach  the  sabot  by  a single  expanding  rivet 
through  its  centre,  the  hole  in  the  projectile  into  which  the 
rivet  fits  being  under-cut,  so  that,  on  a blow  being  given,  the 
end  bulges  out  and  grips  the  edge  of  it.  This  method  is 
preferable  to  the  straps. 

1546.  Advantages. — The  sabot  secures  the  position  of  the 


PREPAE,IXQ  AMiMUI^ITION. 


563 


fuze  in  loading,  which  should  he  in  the  axis  of  the  piece  and 
from  the  cartridge.  It  tends  to  prevent  tlie  formation  of  a 
lodgment  in  the  bore.  It  moderates  the  action  of  the  powder 
on  the  projectile  and  helps  to  keep  the  projectile  in  its  place. 
The  fragments  of  the  sabot  are  scattered  as  soon  as  the  projec- 
tile leaves  the  bore  of  the  piece. 

1517.  Filling  Shells. — All  shell  are  filled  with  shell- 
powder  of  the  highest  initial  velocity.  The  shell  must  be  filled 
and  the  powder  well  shaken  down,  leaving  room  only  for  the 
insertion  of  the  fuze.  A wooden  plug  the  size  of  the  lower 
part  of  the  fuze  will  always  determine  this. 

For  the  purpose  of  increasing  the  effectiveness  of  hollow 
projectiles,  a quick  and  strong  bursting-charge  is  required  to 
break  the  projectile  into  a large  number  of  fragments. 

1548.  The  Chakges  of  Powder  foe  Shell  are  as  fol- 
lows : 


Charges  for  Spherical  Shell. 


XV-inch. 

Xl-incb. 

a 

IX-inch. 

1 VIII. inch. 

•O 

C. 

Boat  and  Field 
Howitzers. 

I3-in.  Bomb. 

24-pdr. 

12  pdr. 

Full 

Charge. 

Bursting 

Charge. 

Blowing 

Charge. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs.  oz. 

lbs.  oz. 

lbs.  oz. 

Bursting  or  Ser^’ice 

Charge. 

13. 

6.00 

4.00 

3.00 

1.85 

0.90 

1.0 

0.5 

11  0 

6 0 

0 6 

Blowing  Charge 

1.0 

0.25 

0.25 

0.25 

0.25 

0.25 

Charges  for  ParrotCs  Shell. 


100-pdr. 

60-pdr. 

30-pdr. 

20-pdr. 

lbs.  oz. 

lbs.  oz. 

75s.  os. 

lbs.  oz. 

3 11 

2 2 

1 8 

1 0 

Charges  for  Dahlgren  Rifle-shell. 


20-pdr 

12-pdr 


0.86  lbs. 
0.50  lbs. 


564 


NAVAL  OEDNANCE  AND  GTJNNEEY. 


The  weight  of  charges  for  shells  vai-ies  slightly  from  those 
given  in  the  tables,  according  to  the  size  of  the  grain  and  den- 
sity of  the  powder. 

1549.  The  Bursting-charges  for  Shell  are  made  np  in  cot- 
ton bags  and  packed  in  separate  tanks.  Shells  are  tilled  by 
capacity,  and  not  by  weight.  When  it  is  not  required  to  burst 
the  shell,  but  merely  to  blow  the  fuze  out  at  practice,  small 
charges  called  “ blowing-charges  ” are  used.  In  naval  pi'aetice, 
however,  it  is  seldom  possible  to  recover  the  shells. 

1550.  Whenever  it  is  necessary  to  load  and  fuze  shell  on 
board  ship — a properly  secured  place  being  first  prepared, 
not  in  the  shell-room,  and  as  far  as  convenient  from  the  maga- 
zine— the  shell,  being  strapped  and  saboted,  are  to  be  exam- 
ined to  see  that  they  ai’e  clean,  both  inside  and  out,  and  thor- 
oughly dry.  The  greatest  care  is  taken  to  remove  every 
particle  of  sand  or  fragment  of  iron  from  the  interior.  The 
pi’escribed  charge  of  powder  is  next  poured  into  them  through 
a proper  funnel,  care  being  taken  that  the  end  of  the  funnel 
passes  below  the  screw-thread  in  the  top,  or  bouching,  to  pre- 
vent any  grains  of  powder  from  entering  it.  Any  grains  of  it 
which  may  remain  sticking  to  the  thread  of  the  bouching  are 
brushed  away  carefully,  and  then,  after  putting  a light  coat  of 
lacquer  for  small-arms,  or  sperm  oil,  on  this  thread  and  on  that 
of  the  fuze,  the  latter  is  screwed  in  carefully  with  the  fuze- 
wrench.  The  fuze  must  be  screwed  in  tight,  care  being  taken 
to  have  the  proper  leather  washer  under  the  head.  The  lacquer 
should  be  of  the  consistency  of  cream,  and  when,  from  evapora- 
tion, it  becomes  too  stiff,  should  be  thinned  by  adding  more 
spirits  of  tmq)entine. 

1551.  The  date  when  shell  are  fuzed  nr  filled,  as  well  as  that 
on  which  any  of  these  arrangements  are  changed,  or  the  shell 
are  examined  before  issue,  together  with  the  initials  of  the  offi- 
cer superintending  these  operations,  should  be  legibly  written 
and  pasted  on  the  shell. 

Projectiles  are  filled  only  as  required  for  ships  fitting  for  sea. 
ilo  pi’ojectile  should  be  fuzed  until  it  has  been  filled,  and  they 
must  be  fuzed  as  soon  as  filled. 

1552.  Packing. — Loaded  shell,  as  well  as  the  sabots  attached, 
are  to  be  painted  red  and  placed  in  boxes  or  bags  marked  with 
a red  cross  on  the  sides,  and  with  the  length  of  fuze  in  black. 

All  spherical  shell  are  packed  singly.  The  smaller  calibres 
of  rifled  shell  are  packed  several  in  a box,  and  the  larger  cali- 
bres singly. 

1553.  Wads. — T^o  wad  is  required  over  a shell,  but  a 
grommet-wad  may  be  used  in  heavy  rolling,  or  to  prevent  the 


PEEPAEING  AMMUOTTIOlSr. 


565 


projectile  moving  forward  slioiild  the  bore  be  depressed;  also 
if  it  is  shaken  by  the  running  out  of  the  gun. 

When  loading  with  shot,  a grommet-^acl  is  placed  oven  it. 
No  wad  is  placed  between  the  charge  and  the  projectile  in 
ordinary  service,  and  it  is  positivelj^  prohibited,  to  place  a wad 
over  an  elongated  projectile. 

1554:.  Geojimet-wad. — This  consists  of  a selvagee,  or  circle 
of  rope  ecpial  in  diameter  to  the  bore  of  the  gun.  They  are 
made  by  a wad-machine.  This  consists  of  pairs  of  disks 
adapted  to  each  calibre  of  guns,  which,  being  placed  face  to 
face  on  a spindle  and  keyed,  present  an  annular  score  grooved 
in  such  a way  as  to  make,  when  fitted,  a grommet  of  the  re- 
quired size.  Transverse  notches  are  cut  in  the  circumference 
of  the  disks  to  the  bottom  of  the  score,  for  the  convenience  of 
marling  the  wad  before  taking  it  off;  the  mold.  In  making  the 
, wad,  the  end  of  a rope-yard  is  left  in  the  score,  and  the  mold  is 
turned  by  a crank  until  the  score  is  filled. 

The  grommet  thus  formed  is  marled  like  a selvagee-strap, 
and  a section  of  about  an  inch  is  taken  out  of  it,  in  order  to 
make  the  wad,  when  swelled  by  the  dampness,  enter  the  bore 
of  the  gun  readily.  Grommet-wads  should  be  made  neither 
too  hard  nor  too  soft ; and  to  avoid  either  of  these  two 
extremes,  a sufficient  number  of  hitches  only  will  be  taken  to 
give  the  wad  the  consistency  i-equired  for  service.  Sections  of 
one-third  or  one-fourth  of  these  wads  will  answer  as  w’ell  in  case 
of  need. 

1555.  Junk-wads. — They  are  now  seldom  used.  They  are 
made  of  oakum  or  cuttings  of  old  “junk”  compressed  into  a 
solid  cylinder  and  bound  around  with  spun  yarn.  They  are 
of  similar  diameter  to  the  bore  of  the  gnu,  and  somewhat  less 
than  one  calibre  in  thickness. 

1556.  Boat  Ammunition. — -When  the  cartridge  is  attaclied 
to  the  projectile,  the  two  together  are  termed  '•'•fixed  ammuni- 
tion ” • this  is  employed  for  service  with  boat-howitzers.  It 
has  the  advantage  of  great  convenience  in  the  hiiriled  prepara- 
tion that  frequently  precedes  boat  operations,  and  the  guns  can 
be  served  more  rapidly  with  fixed  ammunition,  simultaneous 
loading  is  more  simple,  and  the  cartridge  is  sure  to  be  placed 
correctly  in  the  bore,  and  not  with  the  choked  end  first,  as  is 
sometimes  the  case  when  the  projectile  and  cartridge  are  sepa- 
rate. 

Fixed  ammunition  has,  however,  the  disadvantage  that  in 
packing  or  stowing  much  greater  space  is  required,  and  it  is 
more  difficult  to  arrange  and  to  preserve. 


566 


NAVAL  ORDNANCE  AND  GXJNNERT. 


The  charges  for  “ Boat  and  Field  Howitzers  ” are  : 


For  the  2Fpdr.  of  1300  lbs 2.00  lbs. 

For  the  medium  12-pdr.  of  760  lbs . 1.00  “ 

For  the  light  12-pdr.  of  430  lbs 0.625  “ 


The  strength  of  the  pieces  would  justify  greater  charges 
than  these ; but  the  carriages,  the  fixtures,  and  the  frame  of  the 
boat  might  be  injured  by  the  severe  recoil  of  pieces  so  light, 
and  even  be  disabled  by  the  continued  repetition  of  the  firing 
with  heavier  charges. 

1557.  Stand  of  Ammunition. — A stand  of  ammunition  is 
composed  of  the  projectile,  the  sabot,  the 
stra])s,  and  the  cartridge-bag.  (Fig.  339.) 

The  projectiles  used  in  howitzers  are 
shell,  shrapnel,  and  canister. 

For  the  two  former  the  sabot  has  a 
sphencal  cavity  and  a circular  groove  to 
which  the  cartridge-bag  is  tied  ; in  the  latter 
the  spherical  cavity  is  omitted  and  a circular 
olfset  is  added. 

1558.  Packing. — As  soon  as  the  ammu- 
nition is  finished  it  should  be  "ausred  to  see 
that  it  is  of  the  proper  calibre ; it  is  after- 
wards packed  in  well-seasoned  pine  boxes, 
so  disposed  that  the  sabot  may  rest  on  a ledge 
in  the  box,  leavinij  the  chara:e  below  free 
from  any  pressure. 

The  shell,  shrapnel,  and  canister  for  the 
24  and  12  pdr.  howitzers  are  packed  in  boxes  containing  nine 
each.  A fuze-cutter  (for  the  Bormann  fuze)  is  placed  in  the 
rim  of  each  box  containing  loaded  projectiles.  The  boxes  are 
painted  black  and  marked  with  the  contents.  The  Hds  are 
fitted  with  hinges  and  secured  with  screws. 

A key  is  becketed  to  each  box  for  unscrewing  the  lid. 

1559.  In  consequence  of  the  objection  to  packing  powder 
in  wood  on  board  ship,  thereby  rendering  it  more  liable  to  de- 
terioration, various  plans  have  been  suggested  for  fitting  the 
cartridge  to  be  attached  to  the  sabot  at  will,  and  stowing  them 
separately ; and  it  has  been  lately  ordered  that  this  be  done. 

The  cartridge-bag  has  a brass  wire  ring  sewed  into  the  cloth 
outside  of  the  tie,  for  the  puipose  of  attaching  it  to  the  sabot 
of  the  projectile,  the  ring  being  made  to  open  and  fit  into  the 
fillet  of  the  sabot,  being  retained  in  place  by  the  force  of  the 
spring. 


Fig.  339. 


PEEPAEZN-G  AMMUNITION. 


567 


1560.  Metallic  Caeteidges. — ^Tlie  metallic  cartridge  fur- 
nished the  navy  is  a central-primed  metallic  carti'idge,  and  is 
manufactured  by  the  United  States  Cartridge  Company,  Lowell, 
Mass, 

It  consists  of  a brass  case  or  shell  having  a solid  head,  made 
from  one  continuous  piece,  and  by  a peculiar  process  the  metal 
throughout  is  of  the  same  condition,  and  therefore  not  liable  to 
burst  at  the  head  or  rim,  nor  stick  in  the  barrel  of  the  gun  after 
tiring. 

The  method  of  priming  is  very  simple  and  effective,  being 
arranged  so  that  the  case  or  shell,  which  forms  the  greater  part 
of  the  cost  of  the  ammunition,  can  be  reprimed  and  reloaded 
many  times. 

The  primer  consists  of  two  copper  cups  fitting  inside  of  one 
another,  fulminating  compound  being  contained  between  them. 
TJie  inside  or  smaller  cup  has  two  small  perforations  through 
the  bottom  to  allow  for  the  passage  of  the  flame  to  the  charge 
of  powder,  the  bar  formed  between  the  perforations  serving  as 
an  anvil  against  which  the  fulminate  is  exploded. 

The  head  of  the  case  is  made  with  a small  circular  cavity 
for  the  reception  of  the  primer,  the  latter  being  applied  from 
the  outside  ; there  is  also  a perforation  in  the  centre  of  the  cav- 
ity to  allow  the  flame  from  the  primer  to  communicate  with 
the  powder-charge  in  the  case. 

The  charge  of  powder  is  70  grains  ; the  bullet  is  cylindro- 
conical  in  shape,  having  three  rings  and  a concave  base,  and  is 
well  lubricated  ; the  calibre  .50,  weighing  450  grains. 

They  come  in  packages  of  20  each,  and  weigh  2 lbs.  2 oz. 

The  regular  packing-box  contains  50  packages,  or  1,000 
cartridges,  and  weighs  118  lbs.  4 oz. 

The  empty  shells  or  cases  are  to  be  carefully  preserved,  re- 
placed in  their  boxes,  and  returned  to  the  navy-yards  for  re- 
loading. 

1561.  Duiiinr  Caeteedges,  made  of  the  same  size  and  form 
as  the  service  cartridge,  are  supplied  to  ships,  and  must  always 
be  used  during  the  manual  exercise  with  the  Remington  rifle, 
in  order  to  2?i‘event  injury  to  the  striker  by  snapping  the  piece 
at  “Fire.” 

1562.  Blank  Caeteidges  are  supplied  for  funeral  firing 
only  ; they  are  not  to  be  used  in  drill. 

1563.  Incendtaey  Peepaeations  are  fire-stone,  carcasses, 
incencliary-match,  and  hotshot. 

Fire-stone  is  a composition  that  burns  slowly  but  intensely  ; 
it  is  placed  in  a shell  along  with  the  bursting-charge,  for  the 
pm’pose  of  setting  fire  to  ships,  buildings,  etc. 


568 


NAVAL  ORDNANCE  AND  GUNNERY. 


Composition. — It  is  composed  of  ; 

10  parts  of  Hitrej- 
4r  parts  of  Sulphur, 

1 part  of  Antimony, 

3 parts  of  Rosin. 

Preparation. — In  a kettle  in  the  open  air,  melt  together 
one  part  of  nmtton-tallow  and  one  part  of  tui’pentine.  The 
composition,  having  been  pulverized  and  mixed,  is  added  to 
the  melted  tallow  and  turpentine  in  small  quantities.  Each 
portion  of  the  composition  should  he  well  stirred  to  prevent  it 
from  taking  fire,  and  each  portion  should  be  melted  before 
another  is  added. 

IIow  used. — -When  fire-stone  is  to  be  used  in  shell  it  is  east 
into  cylindrical  molds,  made  by  rolling  fuze-paper  around  a 
former  and  securino;  it  with  "lue.  A small  hole  is  formed  in 
the  composition  by  placing  a paper  tube  in  the  centre  of  each 
mold.  When  the  melted  composition  has  become  hard  this 
hole  is  filled  with  a priming  of  fuze-composition. 

The  object  of  this  priming  is  to  insure  the  ignition  of  the 
fire-stone  by  the  flame  of  the  bursting-charge. 

15GI.  Carcass. — A carcass  is  a hollow  cast-iron  projectile 
filled  with  burning-composition,  the  flame  of  which  issues 
through  several  fuze-holes,  to  set  fire  to  combustible  objects. 

The  fuze-holes  are  situated  in  the  upper  hemisphere,  equi- 
distant from  each  other. 

Composition. — The  composition  is  the  same  as  for  port-fires, 
mixed  with  a small  quantity  of  finely  chopped  tow.,  and  as  much 
white  turpentine  and  spirits  of  turpentine  as  avill  give  it  a com- 
pressible consistency. 

Preparation. — The  composition  is  compactly  pressed  into 
the  carcass  Avith  a drift,  so  as  to  fill  it  entirely.  Sticks  of  wood 
one-half  inch  diameter  are  then  inserted  into  each  fuze-hole 
Avith  the  points  touching  at  the  centre,  so  that  when  AvithdraAvn 
corresponding  holes  shall  remain  in  the  composition.  In  each 
hole  thus  formed  tlu’ee  strands  of  quick-match  are  inserted  and 
held  in  place  by  dry  port-tire  composition,  which  is  pressed 
around  them.  About  three  inches  of  the  quick-match  hang 
out  Avhen  the  carcass  is  placed  in  the  piece  ; previously  to  that 
it  is  coiled  up  in  the  fuze-hole  and  closed  with  a patch.  The 
metal  of  a carcass  is  considerably  thicker  than  that  of  a common 
shell,  because,  being  much  Aveakened  by  the  vents,  there  would 
be  danger  of  the  carcass  breaking  up  under  the  shock  of  the 
dischaige  ; and  besides,  as  the  carcass  is  not  required  to  burst, 


PKEPARING  AMMUNITIOIT. 


569 


it  must  have  sufficient  strength  to  withstand  the  pressure 
exerted  upon  it  by  the  gas  which  is  generated  in  the  interior  by 
the  burning-composition. 

A Common  Shell  may  be  loaded  as  a carcass  by  placing  a 
bursting-charge  in  first,  and  covering  it  with  carcass-composi- 
tion driven  in  until  the  shell  is  nearly  full,  and  then  inserting 
strands  of  quick-match  secured  by  driving  more  composition. 
This  projectile,  after  burning  as  a carcass,  explodes  as  a shell. 

1565.  — Incendiaiiy-matcii  is  made  by  boiling  slow-match 
in  a saturated  solution  of  nitre,  drying  it,  cutting  it  into  pieces, 
and  plunging  it  into  melted  fire-stone.  It  is  principally  used 
in  loaded  shells. 

1566.  IIoT-siiOT  may  be  fired  for  the  purpose  of  setting  fire 
to  vessels  or  buildings,  though  they  are  rarely  used.  Shot  of 
low  gauge  should  be  chosen  for  this  purpose  with  reduced 
charges.  They  can  be  made  red-hot  in  from  15  to  30  minutes, 
but  care  must  be  taken  not  to  bring  them  beyond  a hright  red, 
as  they  are  then  liable  to  fuze  and  become  misshapen.  Tlie 
part  resting  on  the  furnace-bars  heats  more  quickly  than  the 
upper  part,  so  they  must  frequently  be  turned.  Shot  expand 
•gig-  of  their  diameter  when  brought  to  a red-heat therefore,  to 
prevent  accidents,  each  shot  should  be  j^assed  through  a red-hot 
shot-gauge  before  being  taken  from  the  fire-room.  Should  the 
shot  jam  iu  the  bore  it  must  be  cooled  by  poiu'ing  water  in  at 
the  muzzle ; but  if  that  fails,  the  charge  must  be  drowned 
before  attempting  to  blow  out  the  shot. 

Precautions  in  Loading. — J unk  and  grommet  wads  which 
have  been  soaked  in  water  for  two  or  three  hours,  and  the 
water  pressed  out  of  them,  are  to  be  used  in  loading.  The 
junk-wads  must  bo  small  enough  to  fit  easily  when  swelled  by 
being  soaked.  The  cartridge  must  be  perfectly  tight,  so  that 
powder  will  not  be  scattered  along  the  bore.  Sufficient  eleva- 
tion having  been  given  to  enable  the  shot  to  roll  home,  first 
enter  the  cartridge,  a dry  junk- wad,  and  then  a wet  junk-wad, 
and  ram  them  home.  Briusr  the  shot  in  a bearer  and  enter  it, 
With  a wet  grommet-wad  on  top;  as  it  cools  rapidly,  no  time 
should  be  lost.  Quantities  of  smoke  will  come  iq)  through  the 
vent,  but  a red-hot  shot  does  not  burn  more  than  the  outer 
yarns  of  a well-soaked  junk-wad,  even  if  left  in  the  gun  till  it 
becomes  cold. 


CHAPTEE  X. 


PEACTICE  or  GUNNERY. 

Section  I. — Service  of  Ordnance. 

1567.  LOADING. — The  charge  is  placed  in  the  muzzle 
with  seams  from  the  vent,  small  end  in  and  tie  outwards.  It  is 
pushed  steadily  to  the  bottom  of  the  bore  and  on  no  account  to 
be  struck.  The  space  which  the  powder  occupies  effects  the 
initial  velocity. 

Cartridges  that  have  left  the  magazine  are  not  to  be  returned 
until  after  the  “ Eetreat  ” is  beaten,  in  order  to  prevent  con- 
fusion. 

Powder-passers  are  to  throw  all  cartridges  that  are  injured 
in  the  slightest  degree  overboard,  or  in  tubs  of  water  prepared 
for  that  purpose. 

TliC  cl  tell  is  entered  sabot  first  and  fuze  out.  xkfter  remov- 
ing the  fuze-cap  it  is  pushed  gently  to  its  place  and  never 
struck. 

1568.  ]\I.:iEKS  ON  EajMmee.— IVith  the  vieAv  of  affording  tlie 
Loader  a certain  and  independent  means  of  knowing  when  tbe 
load  is  really  home,  the  handle  of  the  i-ammer  has  a mailc  upon 
it,  for  the  place  of  both  charge  and  shell,  easily  distinguishable 
either  by  night  or  day. 

This  mark  is  a narrow  circular  indentation,  in  a ]?ortion  of 
which  a strip  of  brass  is  secured,  which  is  marked,  for  the 
outer  one,  with  the  charge  in  pounds,  and  for  the  inner  one, 
with  the  projectile  used. 

1569.  Eemoving  Fuze-patcii.  — In  loading  with  shell,  the  cap 
is  never  to  be  removed  until  the  shell  is  entered  in  the  gun. 
IVitli  high  elevations,  or  when  rolling,  care  should  be  taken 
that  the  shell  does  not  slip  down  tlie  bore  before  this  is  done. 

The  cap  or  patch  is  removed  by  taking  hold  of  the  lug  with 
the  foreiinger  and  thumb,  first  raising  it  a little,  and  without 
twisting ; a pull  readily  removes  it. 

The  patch  is  passed  to  the  Gun  Captain,  as  an  evidence  that 
the  piimiug  lias  been  exposed;  the  patches  are  to  be  preserved 
juui  accounted  for  at  the  end  of  the  tiring. 


LOADING. 


571 


The  Loader  must  be  careful  not  to  touch  the  fuze-composi- 
tion with  iiis  lingers,  for  fear  of  injuring  it  with  moisture. 

In  loading  with  percussion-shell,  the  screw-head  of  the  fuze 
must  be  reversed.  (Art.  1497.) 

1570.  The  XY-inch  Shell,  being  very  heavy,  is  apt  to  slip  in 
the  straps  by  wliich  it  is  secured  to  the  sabot ; therefore,  in  load- 
ing, care  must  he  taken  to  examine  the  position  of  the  fuze-hole. 

When  the  distance  is  known  to  be  less  than  the  range  of  the 
shortest  fuze,  uncap  all  the  fuzes.  At  other  times  uncap  the 
fuze  suited  to  the  distance  and  the  one  of  longest  time  of  burn- 
ing. (Art.  1477.) 

1571.  lYrniDiiAwixG  Peojectiles.— If,  in  loading,  a projec- 
tile jams  in  the  bore,  no  attempt  should  be  made  to  force  it 
down,  but  it  should  be  withdrawn. 

This  may  be  done  with  the  ladle^  by  depressing  and  striking 
the  muzzle  against  the  lower  sill  of  the  port,  or  by  running  the 
gun  out  hard  against  the  side,  at  extreme  depression.  Should 
these  means  fail  to  start  the  projectile,  it  will  be  necessary  to 
destroy  the  charge  by  pouring  water  down  the  vent  and  muzzle, 
and  then  introduce  a small  quantity  of  powder  and  blow  it  out. 

Should  a projectile  jam  in  the  bore  in  action,  the  Gun  Cap- 
tain will  not  attempt  to  withdraw  it,  but  discharge  the  piece  at 
once. 

A gun  is  not  to  be  loaded  wdth  more  than  a single  projec- 
tile, and  solid  shot  are  not  to  be  lired  from  shell-guns  unless 
specially  directed. 

1572.  Cake  ix  the  Use  of  Shell. — In  action,  shell  should 
never  be  allowed  to  accumulate  on  deck.  Experiments  have 
proved  that  any  loaded  shell  at  rest,  when  struck  by  a solid  shot, 
tired  with  even  a moderate  charge  will  be  exploded,  with  force 
sufficient  to  scatter  in  every  direction,  and  to  considerable  dis- 
tances, any  other  shells  that  may  be  placed  in  near  proximity. 

1573.  Keeping  Guns  Loaded. — Guns  should  never  remain 
loaded  longer  than  necessary,  as  the  cartridge  speedily  deterior- 
ates by  the  effects  of  moisture.  If  a shell  has  been  loaded 
twenty-four  hours,  it  should  be  drawn  and  refuzed. 

1574.  Running  Out. — As  the  projectile  slides  in  the  gun 
with  very  little  friction,  particular  care  should  be  talcen  not  to 
let  the  carriage  strike  wnth  too  great  a shock  in  running  out,  as 
it  will  surely  start  the  projectile  from  its  seat. 

1575.  Closing  the  Yent. — After  a piece  has  been  dis- 
charged, the  vent  should  be  cleared  with  the  priming-wire  and 
the  bore  well  sponged  to  extinguish  any  burning  fragments  of 
the  cartridge  that  may  remain. 

To  prevent  the  current  of  air  from  fanning  any  burning 


572 


NAVAL  ORDNANCE  AND  GUNNERY. 


fragments  that  may  collect  in  the  vent,  it  should  be  kept  firmly 
closed  with  a thumb-stall  in  the  operation  of  sponging.  A moist 
sponge  is  always  to  be  used. 

After  sponging,  the  vent  must  again  be  cleared  with  the 
priming-wire  and  closed  with  the  thumb-stall.  These  precau- 
tions are  taken  to  prevent  the  possibility  of  the  vent  becoming 
obstructed. 

157G.  Cleaeing  the  Yent. — If  at  any  time  the  Gun  Cap- 
tain should  find  the  veat  obstructed,  and  be  unable  to  clear  it 
wdth  i\\Q,  primin'j-wire  or  l/oring-hit,  he  wall  at  once  report  to  the 
officer  of  the  division,  who  will  order  the  vent-punch  used ; or. 
if  this  should  fail,  have  recourse  to  the  vent-drill  and  l>race  in 
charge  of  the  Quarter  Gunner.  The  boring-bit,  vent-punch,  and 
drills  should  be  used  with  caution,  as,  being  of  steel,  they  are 
liable  to  be  broken  oil  in  the  vent  and  thus  eSectually  spike  the 
gun. 

After  clearing  the  vent,  the  bore  should  be  sponged. 

1577.  Spongers  ^vnd  Loaders  should  keep  their  bodies  clear 
of  the  muzzle,  and  as  much  within  the  poi't  as  practicable  for 
their  own  protection. 

1578.  li ARIDITY  OF  Loading. — Loading  can  not  be  executed 
with  too  much  rapidity,  provided  neither  the  safety  of  the  gun 
nor  of  its  crew  be  compromised. 

1579.  Use  of  Projectiles  not  adapted  to  the  Piece. — If 
it  should  become  necessary  to  use  a projectile  much  smaller  than 
the  bore,  it  is  strapped  to  a stout  sabot  which  fits  the  bore  ; if 
a mortar-shell,  it  is  placed  in  the  centre  of  the  bore  with  wedges 
and  the  surrounding  space  is  filled  up  with  earth  or  old  junk. 

We  may  also  fire  fi-om  a gun, shot  of  a greater  calibre  placed 
upon  the  muzzle ; this  species  of  fire  is  generally  at  an  angle  of 
45° ; the  bomb  placed  upon  the  muzzle  is  secured  by  a cord 
which  is  broken  by  the  first  impulse ; the  accuracy  is  nearly 
equal  to  that  of  shells  from  a mortar,  and  the  rangeof  an  S-iuch 
shell  fired  from  a 24-pdr.  camion,  with  8 lbs.  charge  of  powder, 
is  about  GOO  yards : the  shorter  the  gnu,  the  greater  the  range. 

1580.  Loading  Mortars.  — The  powder  is  to  be  emptied  into 
the  mortar  from  the  cartridge-bag.  which  must  be  well  shaken 
to  remove  dust  and  fine  grains  of  powder.  The  bag  is  re- 
tained in  the  hands  of  the  Loader  to  be  used  in  wiping  the  shell 
before  it  is  lowered  into  the  bore.  The  powder  is  levelled  off 
wdth  a sjyatula,  wdien  the  bomb,  loaded  and  fuzed,  is  carefully 
lowered  into  the  bore  by  the  hooks,  and  allowed  to  rest  upon 
the  charge,  keeping  the  fuze  exactly  in  the  axis  of  the  bore.  In 
mortars,  where  a sponge  is  seldom  used,  the  stopping  of  the 
vent  is  not  necessary ; but  it  should  always  be  cleared  out  wdth 


LOADING. 


573 


the  priming-wire  before  the  powder  is  placed  in.  The  bore  is 
cleared  with  a scraper,  and  wiped  out  Avith  an  empty  cartridge- 
b.ag  or  swab.  If  a sponge  is  used,  it  is  much  smaller  than  the 
bore. 

1581.  Loadustg  Swall-aems.— Bring  the  piece  to  full-cock 
and  open  the  breech-block ; if  there  be  an  empty  sliell  in  the 
chamber,  it  Avill  be  removed  by  the  extractor.  The  firing-pin 
may  be  made  to  protrude  by  being  choked  with  rust,  or  by 
wedging  of  the  firing-pin  spring,  and  in  this  position  lead  to  a 
premature  explosion  in  closing  the  breech-block.  Pass  the  fin- 
ger over  the  face  of  the  breech-block,  to  ascertain  that  the  firing- 
pin  does  not  protrude. 

Place  the  cartridge  in  the  chamber  and  close  the  breech- 
block. Should  there  be  any  difficulty  in  closing  the  breech- 
block, it  is  probable  that  the  rim  of  the  cartridge  is  too  thick ; it 
should  be  AvithdraAvn  and  another  tried. 

The  chamber  should  be  kept  clean,  and  great  care  observed 
to  prevent  cartridges  fouled  with  dirt,  and  particularly  sand, 
from  being  inserted  or  discharged  in  the  piece,  as  the  expansion 
of  the  shell  presses  the  sand  into  the  metal  and  mars  the  surface 
of  the  chamber,  and  thus  causes  the  shells  to  stick.  Care  should 
also  be  taken  in  cleaning  the  chamber  for  the  same  reason.  The 
shell  of  an  exploded  cartridge  should  not  be  allowed  to  remain 
in  the  chamber  any  length  of  time,  for  fear  it  may  adhere  by 
corrosion. 

To  prevent  premature  discharges,  and  to  relieve  the  firing- 
pin  spring,  the  piece  should  be  always  kept  at  half-cock. 

In  coming  to  “ order  arms,”  the  butt  should  be  brought  to 
the  deck  Avithout  shock,  as  a jar  may  injure  the  piece. 

1582.  POINTING. — To  point  or  aim  a fire-arm  is  to  give 
it  such  direction  and  eleA'ation  that  the  projectile  shall  strike  the 
object.  To  do  this  properly,  it  is  necessary  to  understand  the 
relations  Avhich  exist  betAveen  the  line  of  sight,  line  of  fire,  tra- 
jectory, etc. 

1583.  DErnsrmoNS. — The  line  of  sight  is  the  right  line  con- 
taining the  guiding  points  of  the  sights.  The  sights  are  two 
pieces  on  the  upper  surface  of  the  gun,  the  situation  of  which 
with  regard  to  the  axis  of  the  bore  is  known. 

H]xQ  front  sight  is  usually  situated  between  the  trunnions  or  * 
on  the  rim  base,  and  is  generally  fixed  ; the  rear  sight  is  placed 
on  the  breech,  and  is  movable  in  a vertical  plane. 

The  natural  line  of  sight  is  the  line  of  sight  nearest  the  axis 
of  the  piece ; the  others  are  called  artificial  lines  of  sight. 

The  line  of  fire  is  the  axis  of  the  bore  prolonged  in  the  di- 
rection of  the  muzzle. 


574 


NAVAL  ORDNANCE  AND  GDNNEET. 


The  angle  of  fire  is  the  angle  incliicled  between  the  line  of 
fire  and  horizon  ; on  account  of  the  balloting  of  the  projectile, 
the  angle  of  the  fire  is  not  always  ecpial  to  the  angle  of  depart- 
ure or  projection. 

T\xq  angle  of  sight,  or  angle  of  elevation,  is  the  angle  in- 
cluded between  the  line  of  sight  and  line  of  fire ; angles  of  sight 
are  divided  into  natural  and  artificial  angles  of  sight,  corre- 
sponding to  the  natm-al  and  artificial  lines  of  sight  which  enclose 
them. 

T\xq  plane  of  fire  the  vertical  plane  containing  the  line  of 
fire. 

H\\Q  plane  of  sight  h the  vertical  plane  containing  the  line 
of  sight. 

1584.  Point-blank. — The  term  originated  when 

it  was  imagined  that  a shot  travelled  for  some  distance  in  a 
straight  line,  or  direct ; it  is  of  no  practical  use,  and  is  difter- 
entlv  defined  in  diSerent  countries. 

The  French  definitions  oi  pomt-hlanh  scad,  point-hlanh  range 
are  as  follows : 

The point-hlanli  is  the  second  point  at  whicdi  the  line  of 
sight  intersects  the  traj ectory ; and  the  distance  from  the' face 
of  the  muzzle  to  this  point  is  the  point-hlanh  range. 

The  natural point-hlanli  corresponds  to  the  natural  line  of 
sight ; all  other  points-blank  are  called  artificial  pomts-hlanh. 

In  the  British  service,  as  well  as  in  our  own,  the  point-blank 
distance  is  the  distance  at  which  the  projectile  strikes  the  hori- 
zontal plane  on  which  the  trucks  of  the  carnage  rest,  the  axis 
of  the  jiiece  being  horizontal. 

1585.  Eange  is  the  distance  from  the  muzzle  of  the  gun  to 
the  second  intersection  of  the  trajectory  with  the  line  of  sight. 

In  practice  the  range  is  usually  measured  from  the  muzzle 
to  the  point  of  impact  on  the  object,  or  to  the  first  graze  of 
the  projectile. 

The  ]-ange  depends  upon  the  initial  velocity,  the  form,  anrl 
density  of  the  projectile,  the  angle  of  elevation  of  the  gun.  and 
the  ditference  of  level  between  the  planes  upon  which  the  gun 
and  object  respectrtely  stand. 

Extreme  range  is  the  distance  to  the  point  at  which  the  pro- 
jectile is  brought  to  a state  of  rest. 

1586.  Range  at  Level. — The  gun  being  placed  a certain 
height  above  the  water,  depending  on  the  class  of  vessel  and 
the  deck  on  which  it  is  mounted,  it  is  evident  that,  when  the 
axis  of  the  bore  is  horizontal,  the  projectile  ■will  have  a range 
proportionate  to  this  height. 

The  distance  to  which  the  projectile  wiU  range  in  this  case, 


SIGHTING  CANNON. 


575 


before  it  grazes  the  Avater,  is  called  the  range-at-le.vel,  and  de- 
pends npon  the  class  of  gun,  the  cJiarge,  and  the  height  above 
the  water. 

1587.  SIGHTIh7G  CAhllSlOiSl. — In  order  that  a projectile 
fired  from  a gun  may  strike  a required  object,  it  is  necessary  to 
adjust  the  line-of-fire  with  reference  to  the  horizon  and  the  ver- 
tical plane  passing  through  the  object  in  such  a manner  that 
the  trajectory  will  reach  it. 

The  axis  of  the  gun  is  not  visible,  and  it  is  necessary  to 
resort  to  notches  or  sights  on  the  exterior  surface  to  determine 
practically  the  position  of  the  axis. 

The  line  of  meial  is  a visual  line,  joining  the  notches  cut 
on  the  highest  points  of  the  base-ring  and  swell  of  the  muzzle. 

The  inclination  of  the  line  of  metal  to  the  axis  of  the  bore 
varies  in  guns  of  the  same  class  as  well  as  in  those  of  different 
classes.  Aiming,  therefore,  by  the  line  of  metal  cannot  be 
relied  on  for  definite  ranges  ; besides  that,  within  those  ranges 
it  is  apt  to  mislead  by  giving  too  much  elevation  to  the  piece. 
If  a gun  be  pointed  at  an  object  by  means  of  a line  of  metal,  it 
will  be  seen,  by  prolonging  that  line  and  the  axis  of  the  bore, 
that  the  latter  will  pass  over  the  object. 

1588.  Dispart-sight. — A dispart  is  a piece  of  metal  placed 
on  the  top  of  the  gun  to  give  a line-of-sight  parallel  to  the  axis 
of  the  bore. 

The  dispart  is  generally  defined  as  half  the  difference  be- 
tween the  diameters  of  those  parts  of  the  gun  lopon  which  the 
sights  are  placed. 

Half  the  difference  between  the  diameters  of  the  gun  at 
the  base-ring  and  swell  of  the  muzzle,  or  at  any  intermediate 
])oint  on  the  line  of  metal,  will  give  the  proper  height  of  the 
dispart-sight  at  the  point  where  the  least  diameter  was  taken. 

In  the  absence  of  other  means  of  sighting,  wooden  dispart- 
sights  lashed  on  the  reenforce  can  be  used.  A narrow  groove 
in  the  upper  surface  of  the  wooden  sight,  made  to  coincide  with 
the  plane  of  the  line-of-sight  marked  on  the  gun,  will  assist  in 
getting  the  true  direction. 

The  guns  of  the  Dahlgren  pattern  are  cylindrical  for  a cer- 
tain distance  forward  of  the  base-line,  always  giving  a line-of- 
sight  parallel  to  the  axis  of  the  bore. 

Guns  are  marked  on  the  top  of  the  base-ring,  the  sight- 
masses,  and  swell  of  the  muzzle,  by  notches,  wliicti  indicate  a 
vertical  plane  passing  through  the  axis  of  the  bore  at  right- 
angles  to  the  axis  of  the  trunnion. 

In  range-at-level,  the  bore  being  horizontal,  the  dispart- 


576 


NAVAL  ORDNANCE  AND  GUNNERY. 


sight  is  directed  at  a point  above  the  water-line  or  point  struck 
equal  to  its  own  distance  above  that  line. 

If  the  gun  is  pointed  by  dispart  directly  at  an  object,  the 
projectile  will  fall  short,  more  or  less,  depending  upon  the 
distance. 

In  pointing  by  dispart,  therefore,  it  is  necessary  to  direct 
the  sight  a certain  height  above  the  object,  to  allow  for  the  fall 
of  the  projectile  during  flight ; the  height  to  be  pointed  above 
must  depend  upon  the  distance  of  the  object. 

1589.  Tangent  Fieing. — Before  the  introduction  of  the 
tangent  scale  or  breech-sight,  all  pointing  at  sea  was  done  with 
the  dispart-sight.  When  desiring  to  strike  an  object  beyond  the 
range-at-level  of  the  piece,  it  was  necessary  to  direct  the  line- 
of  sight,  which  was  parallel  to  the  axis  of  the  piece,  at  a point 
a certain  distance  above  the  object ; this  elevation  being  in- 
tended to  allow  for  the  space  through  which  the  projectile 
falls  by  the  action  of  gravity  in  the  time  of  flight. 

The  vertical  space  through  which  the  projected  body  in  its 
flight  descends  below  the  line  of  fire  is  equal  to  the  tangent  of 


D 


the  angle  of  elevation  multiplied  by  the  range  or  horizontal 
distance  of  the  object  from  the  gun. 

BD 

In  the  figure  (310),  tan  A = 

BD  = AB  tan  A. 

Thus,  suppose  a gun  to  be,  at  A,  at  a known  height,  AA', 
above  the  level  of  the  water  and  at  a known  distance,  AB,  from 
a vertical  object,  B'D,  as  a ship’s  mast.  For  any  particular 
nature  of  ordnance  we  know  the  elevation  necessary  to  project 
the  projectile  a certain  distance. 

ISTow  in  the  equation 
BD  = AB  tan  A, 

AB,  equal  to  the  distance,  is  known,  as  is  also  the  angle  A, 
which  is  the  angle  of  elevation  necessary  to  give  the  gun  in 


SIGHTING  CANNON. 


577 


order  to  project  the  ball  the  distance,  AB.  But  we  have 
no  means  of  pointing  the  gun  at  this  angle,  except  by  finding 
the  length  of  the  vertical,  Avliich  will  subtend  this  vertical 
angle  at  the  distance  of  the  object.  The  required  length  of 
the  vertical,  BD,  is  found  by  the  ecpiation, 

BD  = AB  tan  A. 

If,  then,  the  line  of  sight  parallel  to  the  axis,  be  directed  at 
the  point  D,  we  know  that  the  gun  has  the  elevation  that  is 
required  in  order  to  make  the  ball  reach  to  the  distance,  AB. 
Adding  to  both  sides,  BB',  Ave  have 

B;D  = AB  tan  A + BB'. 

To  strike  an  object,  then,  at  the  water-line,  at  the  distance 
AB,  greater  than  the  range  at  level,  the  aim  being  taken  with 
the  dispart-sight,  it  is  necessaiy  to  direct  the  line  of  sight  at  a 
point  situated  at  the  distance,  B'D,  above  the  water-line. 

The  heights  of  certain  points  on  the  masts  of  foreign  men- 
of-war  being  known,  tables  have  been  constructed,  in  the 
columns'  of  which  are  designated  the  points  at  which  the  line 
of  sight  must  be  directed,  corresponding  to  certain  distances  of 
the  object  which  it  is  desired  to  hit.  Such  tables  are  to  be 
found  in  the  old  editions  of  the  Ordnance  Instructions. 

This  mode  of  firing  presents  serious  disadvantages.  The 
points  arrived  at  have  often  to  be  estimated,  as  well  as  the  dis- 
tance of  the  enemy’s  vessel : the  class  of  which  can  seldom  be 
accurately  determined.  The  men  are  taught  to  aim  where 
they  are  not  expected  to  hit,  and  the  chances  of  the  ricochet 
are  lost  ; hence,  tangent  firing  should  only  be  resorted  to  when 
there  are  no  other  means  of  regulating  the  elevation  of  the 
guns. 

1590.  Tangent  Sights. — To  facilitate  the  operation  of 
pointing  guns  according  to  the  distance  of  the  object  aimed  at, 
sights  are  prepared  and  fitted  to  each  gun. 

The  ordinary  sights  consist  of  two  pieces  of  bronze  gun- 
metal,  one  of  which,  called  the  reenforce  or  dispart-sight,  is  a 
fixed  point,  firmly  secured  to  the  sight-mass,  upon  the  upper 
surface  of  the  gun  between  the  trunnions. 

The  other,  or  breech-sight,  is  a square  bar  or  stem  with  a 
head,  in  the  top  of  which  is  a sight-notch.  It  is  set  diagonally 
so  as  to  expose  two  faces  to  the  rear ; the  rear  angle  chamf erred, 
to  afford  a bearing  for  the  clamp-screw.  This  bar  or  stem  is 
made  to  slide  in  a vertical  plane,  in  the  sight-box  fixed  to  the 
breech-sight  mass,  and  is  held  at  the  various  elevations  tor 
which  it  is  graduated  by  means  of  a thumb-screw.  Its  length 
is  sufficient  for  all  the  elevation  which  can  be  given — about  5° 
— before  the  muzzle  appears  above  the  front  sight,  after  which 
37 


578 


NAVAL  ORDNANCE  AND  GUNNERY. 


a long  wooden  sight  must  be  used,  graduated  for  the  whole 
length  of  the  gun,  using  the  notch  in  the  muzzle. 

1591.  The  brass  tangent-scale  or  breech-sight  may  he  said 
to  be  a tangent  to  an  arc  the  radius  of  which  is  the  distance 
from  the  outer  point  of  the  fore-sight  to  the  fore  part  of  the 
hind-sight,  and  the  divisions  are  calculated  accordingly ; this 
distance  is  called  the  short  radius. 

The  wooden  tangent-scale  may  be  said  to  be  a tangent  to 
an  arc  of  which  the  radius  is  the  distance  from  the  notch  on 
the  swell  of  the  muzzle  to  the  front  of  the  hind-sight ; this 
distance  is  called  the  long  radius. 

The  tangent-scale  is  set  at  an  angle  of  60°,  so  that  it 
may  slide  up  and  down  without  touching  the  breech  of  the 
piece. 

Every  gnu  is  furnished  with  two  sight-bars,  a long  wooden 
and  a short  brass  one  ; the  longer  is  used  for  ranges  over  1,700 
yards  ; for  all  ranges  less  than  this,  which  is  the  extreme  dis- 
tance at  which  accurate  practice  may  be  expected  at  sea,  the 
short  bar  is  used. 

1592.  Pivot  Guns  have  their  tangent-scales  fitted  to  be 
placed  on  the  side  of  the  breech,  and  the  forward-sight  is 
placed  on  the  trunnion  or  rim-base. 

The  advantage  of  this  arrangement  is  that  the  tangent  and 
trunnion  sights  can  be  used  at  any  elevation ; for,  being  placed 
at  the  side  of  the  gun,  the  muzzle  of  the  piece  does  not  inter- 
fere with  the  line  of  sight  when  pointing. 

The  sights  of  all  howitzers  are  fitted  in  this  way  : 

1593.  Sights  for  Pi  fled  Gions. — These  consist  of  a fixed 
sight  upon  the  right  rim-base,  and  a brass  movable  sight  in  a 
socket  which  is  screwed  into  the  rear  of  the  reenforce  at  the 
breech  of  the  gim.  The  movable  sight  is  furnished  with  a 
sliding  eye-piece,  and  is  graduated  up  to  10°.  The  eye-piece 
is  also  capable  of  lateral  adjustment  to  allow  for  the  drift  as 
far  as  10°,  and  for  the  effect  of  the  wind.  It  is  desirable  that 
the  sights  should  be  placed  on  both  sides  of  the  breech  ; other- 
wise, in  firing  from  a port  at  extreme  train,  there  may  be  con- 
siderable loss  of  lateral  aim. 

1594.  The  radius  between  the  sights  should  bo  as  long  as 
possible  for  sea-practice,  with  an  unsteady  platform,  and  where 
the  eye  is  far  removed  from  the  rear-sight. 

In  order  to  see  the  object  in  line  with  the  outer  sight,  the 
eye  must  pass  a certain  vertical  distance  above  the  rear-sight. 
The  amount  of  vertical  height  between  the  rear-sight  and  the 
line  of  vision  depends  upon  the  state  of  the  weather,  and  upon 
the  motion  of  the  ship.  When  the  shij)  is  steady  it  will  prob- 


SIGHTING  CANNON. 


579 


ably  be  0.1  or  0.2  of  axi  incli.  When  the  ship  is  very  lively 
it  may  be  half  an  inch. 

At  all  known  distances,  all  considerable  errors  in  firing  at 
sea  are  dependent  upon  the  height  that  the  line  of  vision 
passes  above  the  rear-sight.  Take  a given  vertical  height  of 
visual  error,  say  half  an  inch  : the  effect  it  will  have  upon  the 
range  depends  upon  the  distance  between  the  sights ; if  they 
are  but  a few  inches  apart,  the  error  will  cause  some  thousands 
of  yards  increase  of  range. 

If  they  are  as  far  apart  as  they  can  be  placed,  the  same 
visual  error  will  probably  cause  an  error  in  range  of  less  than  a 
100  yards  with  a IX-inch  gun. 

1595.  Adjustment  of  the  Sights.'^ — Roll  the  gun  in  the 
direction  of  its  trunnions  until  the  line  of  sight  is  uppermost. 
The  cylindrical  portion  of  gun  forward  of  base-ring  is  supposed 
to  be  turned  at  the  foundry  parallel  to  axis  of  bore,  so  the  next 
object  is  to  trim  down  the  reenforce  and  breech  sight-masses  un- 
til they  are  level  with  the  cylindrical  portion  of  gun.  To  do 
this,  scrape  off  all  the  paint  wdiich  may  be  on  the  gun  in  line  of 
sight.  Place  a straight-edge  on  the  portion,  its  two  ends  rest- 
ing respectively  on  the  reenforce  and  breech  sight-masses.  Trim 
down  both  masses  until  daylight  cannot  be  seen  between  the 
straight-edge  and  the  gnu  along  its  whole  length  where  the 
straight-edge  takes, 

1596.  If  possible,  all  sighting  of  guns  should  be  done  under 
cover,  as  the  wind  outside  deflects  the  thread  of  the  tompion-arm 
when  fixing  the  point  of  the  reenforce-sight.  If  the  gun,  how- 
ever, is  out  of  doors  and  difficult  to  move,  build  a screen,  fore 
and  aft,  the  length  of  the  gun  to  windward.  The  gun  being  in 
Gun  Park,  lying  on  wooden  skids  taking  at  chase  and  breech, 
build  up  with  blocks  under  muzzle  and  at  trunnions,  using  these 
in  connection  with  chocks  to  bring  the  gun  to  an  exact  level 
both  as  to  axis  of  bore  of  gun  and  axis  of  trunnions. 

1597.  The  bore  having  been  thoroughly  cleansed,  its  axis  is 
levelled  by  inserting  a smalt  steel  T-scpiare  in  bottom  of  bore  at 
the  muzzle.  The  scpiare  itself  is  first  levelled  by  placing  an  or- 
dinary level  on  the  transverse  Ixrauch.  When  the  T-square  is 
levelled,  the  level  is  then  placed  on  the  longitudinal  branch 
of  the  T-square  lengthwise  with  the  bore  of  gnu,  and  the  axis 
of  gun  is  then  levelled  by  strilcing  the  chocks  previously  placed 
on  each  side  under  chase  of  gun,  which  of  course  either  raise  or 
lower  the  muzzle.  When  the  gun  has  been  levelled  as  to  axis 
of  bore,  it  is  to  be  levelled  as  to  axis  of  trunnions. 


By  Lieutenant  C.  IL  West,  U.  S.  Navy. 


580 


NAVAL  ORDNANCE  AND  GUNNERY. 


1598,  To  level  as  to  axis  of  trunnions;  First,  scrape  o2  the 
paint  on  top  of  each  trunnion,  then  place  the  trunnion-square 
as  seen  in  h'ig.  311,  and  put  the  spirit-level  on  it  as  at  s.  Ad- 


Fig.  341. 


just  the  piece  by  means  of  the  chocks  under  the  tninnions  until 
they  are  horizontal.  This  levelling  the  gun  by  axis  of  trunnions 
may  throw  out  the  axis  of  gun-level,  in  which  case  return  to 
that,  and  then  to  the  other,  approximating  closer  and  closer 
each  time  until  the  gun  is  levelled. 

If  the  gun  be  lying  on  wooden  skids,  the  levelling  must  be 
verified  from  time  to  time,  as  the  great  weight  will  cause  it  to 
sink  trifle  by  trifle,  thus  throwing  the  level  out. 

1599.  Fitting  Centee-sigiits. — The  gun  being  levelled,  next 
proceed  to  find  initial  point  on  base-ring.  Encircle  the  breech 
of  the  gun  at  the  base-ring  with  the  trunnion-square,  first  scraping 
off  the  paint  on  gun  where  the  legs  of  square  take  on  either 
side,  and  level  the  square  by  a spirit-level.  Then  take  the  slid- 
ing pointer  on  transverse  branch  of  square,  and  set  it  at  a point 
exactly  half  way  on  the  branch,  by  means  of  the  graduated  scale. 
Hit  the  gun  on  the  base-ring  a slight  tap  with  the  pointer. 
Take  the  square  oS  and  turn  the  legs  end  for  end,  again  em- 
bracing the  gun,  and  again  level  square  with  spirit-level.  Again 
hit  the  gun  on  the  base-ring  a slight  tap  with  the  jiointer. 
Should  the  pointer  not  strike  in  the  same  point  as  it  did  in  the 
first  instance,  choose  a point  half  way  between  the  two  for  the 
initial  point. 

IGOO,  The  initial  point  on  base-ring  being  determined,  place 


Fig.  342. 


the  sighting-tompion  (Fig.  3-12)  in  bore  of  gun.  When  the 
tompion  is  being  placed  in,  be  guided  by  the  rings  on  the  side  to 


SIGHTING  CANNON. 


681 


insert  it  evenly^  so  as  to  prevent  jamming.  In  large  calibres  it 
is  also  better  to  close  the  vent  before  inserting  tlie  tompion,  as 
thus,  Tvitli  the  compressed  air,  it  can  be  taken  ont  more  easily. 
Adjust  the  vertical  arm  of  tompion  by  the  spirit-level  and  tan- 
gent-screw. Extend  the  thread  from  vertical  arm  to  the  rear, 
resting  for  a second  point  on  the  initial  point  established  by 
trunnion-square  on  base-ring. 

1601.  blow  with  a slight  dent  of  the  centre-punch, mark  the 
point  where  the  thread  crosses  the  reenforce  sight-mass.  Take 
a straight-edge  and  lay  it  in  the  straight  line  determined  by  the 
two  points,  namely,  the  initial  point  on  base-ring  and  the  point 
determined  on  the  reenforce  sight-mass  by  thread  of  tompion- 
arm.  Take  a scriber  and,  with  the  straight-edge  lying  on  these 
two  points,  scribe  out  a centre-line  on  the  cylindrical  portion  of 
breech,  also  extending  the  line  to  the  rear  sight-mass. 

1602.  Proceed  to  cut  out  the  breech  sight-mass  to  its  proper 
size  (using  as  an  initial  line  the  line  just  described  by  means  of 
straight-edge).  For  proper  width,  length,  and  bevels  of  breech 
sight-mass  use  templets  and  gatiges.  There  is  a standard  distance 
given  for  distance  of  front  part  of  rear  sight-mass  from  base-ring. 

1603.  As  soon  as  the  rear  sight-mass  is  marked  out  by  the 
templets,  proceed  to  cut  down  the  mass  and  lit  rear  sight-box. 
To  tit  the  rear  sight-box  so  as  to  bring  the  rear  sight-box  to 
proper  angle,  and  also  to  a true  plane  perpendicular  to  axis  of 
trunnions,  use  the  levelling-bar.  (Fig.  343.)  Lay  the  reenforce- 
sight  on  the  reenforce  sight-mass.  Then  lay  the  levelling-bar 
with  one  end  on  the  reeenforce  sight,  the  sight  taking  in  the 
line  scribed  on  bottom  of  levelling-bar. 

1604.  The  Levelling-har,  B (Fig.  343),  is  a square  steel  bar 
with  parallel  faces,  somewhat  longer  than  the  distance  between 
the  sights  on  the  largest  gun.  The  rear  end  is  bevelled  at  an 
angle  of  60°,  the  angle  at  which  the  sight  is  placed.  It  has  a 


B S 


Fro.  343. 


central  line  marked  on  it  throughout  its  length,  on  the  under 
side,  and  along  the  bevelled  end.  It  has  also  marked  on  its 
sides,  near  the  forward  end,  the  distance  at  which  the  sights 
should  be  placed  for  each  class  of  gun.  It  is  also  fitted  with 
screws’  for  bringing  it  to  a level. 


582 


NAVAL  OEDNANCE  AND  GUNNERY. 


1605.  The  levelling-bar  being  laid  on  the  reenforce-sight,  and 
its  bevelled  end  taking  against  the  rear-sight-bar,  bring  it  to 
a level  with  the  spirit-level  and  screws.  This  Avill  give  the 
true  guide  for  angle  of  rear-sight-bar,  and  the  latter’s  proper 
plane.  As  soon  as  rear-sight-box  is  fitted,  bore  hole  for  same 
through  rear-sight-mass.  This  hole  is  bored  with  the  rear-sight- 
box  on,  and  the  latter  is  kept  down  in  its  place  by  a sling 
around  cascabel  set  up  by  a handspike. 

1606.  The  rear-sight  being  fitted  tnie  as  to  the  levelling-bar, 
again  level  the  arm  of  sighting-tompion,  and  stretch  the  thread 
back  over  gun,  this  time  bringing  the  thread  to  the  exact  mid- 
dle of  the  rear-sight-bar  notch.  Kow  in  theoiy,  the  thread 
ought  to  come  directly  over  the  initial  point  of  base-ring,  and 
over  the  mark  already  laid  off  on  reenforce-sight-mass ; but 
practically  this  is  never  the  case,  as  it  is  almost  irnpossihle  to  fit 
a rear-sight  box  so  true  as  to  bring  the  middle  of  the  sight- 
notch  in  the  exact  line  of  sight  already  laid  off.  It  will  be 
found,  upon  stretching  the  thread  the  second  time,  that  it  will 
fall  a trifie  one  side  or  other  of  the  initial  point  on  base-ring. 
8o,  virtually,  it  is  necessary  again  to  lay  o3  a line  of  sight. 

1607.  With  a measure  take  the  distance  that  the  thread 
falls  to  one  side  of  the  initial  point  on  base-ring.  Take  this  same 
distance  that  the  thread  is  out,  and  lay  it  off  horizontally  on 
the  cross-bar  of  the  vertical  sighting-arm.  Of  course  when  the 
thread  is  also  moved  this  distance  on  the  sighting-arm,  the 
thread  will  fall  the  same  distance  to  one  side  on  the  reenforce- 
sight-mass  ; therefore  mark  this  last  point  where  the  thread  falls 
over  the  reenforce-sight-mass,  and  thus  is  established  the 
second  and  final  line  of  sight.  Also  mark  the  point  where  the 
thread  now  crosses  the  base-ring,  and  this  is  the  final  initial 
point  to  be  marked  for  a fall  due  on  the  base-ring.  Where  the 
thread  crosses  the  reenforce-sight-mass,  hold  the  reenforce- 
sight  itself  directlj'  under  the  thread.  When  the  reenforce- 
sight-mass  was  lined  out,  at  the  same  time  with  the  breech- 
si<jht-mas3,  a regulation  distance  Avas  given  from  base-rins:  to 
centre  of  reenforce-sight-mass,  and  from  this  central  pomt  the 
mass  was  marked  out  and  cut. 

1608.  To  Fit  Sight  on  lieenforce-Sight  Mass. — Holding  the 
sight  directly  under  the  thread,  mark  out  the  places  of  the  screw- 
holes  on  mass.  These  screw-holes  are  then  drilled  and  tapped. 
The  reenforce-sight  being  screwed  on  to  the  mass,  cut  off  a cer- 
tain portion  of  tlie  steel  bar  in  the  sight,  determined  as  follmvs: 
Let  the  rear-sight  bar  drop  to  a level.  Then  lay  the  levelling- 
l)ar  on  gun  as  in  determining  the  angle  of  rear-sight  bar.  A 
distance  is  given  on  the  levelling-bar  from  rear-sight  bar  to  for- 


SIGHTING  CAIOTON. 


583 


ward  part  of  tlie  steel-bar  of  the  reenforee-sight,  and  tliis 
distance  being  measured,  cut  off  all  tbe  steel  bar  of  reenforee- 
sight  which  is  over. 

1609.  After  the  reenforce-siglit  is  finally  fitted  as  above 
described,  again  stretch  the  sighting-tompion-thread  over  all 
parts,  and  the  thread  must  coincide  as  follows : it  must  pars 
directly  o\'er  the  steel  bar  of  the  reenforee-sight ; then  directly 
over  the  initial  point  on  base-ring,  and  then  directly  through 
the  exact  middle  of  the  notch  of  the  rear-sight-bar.  This  must 
be  particularly  obsei’ved  Avhen  inspecting  the  gun  for  final 
stamping  of  Inspector’s  initials. 

1610.  ISlext  to  determine  the  amount  of  shoulder  that  the 
rear-sigh t-bar  is  to  have.  The  projection  on  head  of  sight-bar 
that  takes  on  rear-sight-box  is  called  the  shoidder  of  sight-bar. 
This  is  done  by  again  putting  the  levelling-bar  on  reenforee- 
sight,  and  bringing  it  to  a level  by  the  spirit-level.  The 
shoulder  is  then  trimmed  down  until  daylight  can  be  just  seen 
through  the  notch  when  the  rear-sight-bar  rests  on  sight-box. 
Do  not  cut  the  shoulder  down  so  low  that  the  extreme  tip  of 
the  reenforee-sight  can  be  seen,  as  that  will  bring  the  rear- 
sight-bar  too  low.  The  bar  is  then  graduated  by  the  scale  fur- 
nished. On  no  account  must  the  bar  be  cut  as  to  the  shoulder, 
after  being  stamped. 

1611.  To  mark  the  lioie  of  sight  on  swell  of  mnzzle. — 
Again  stretch  the  thread  from  arm  of  sighting-tompion  to  mid- 
dle of  notch  of  rear-sio;ht,  at  the  same  time  raisina;  the  rear- 
sight  to  its  greatest  elevation,  and  lowering  the  thread  on 
vertical  arm  of  tompion.  This  of  course  brings  the  thread 
down  to  touch  the  swell  of  the  mnzzle,  and  it  is  there  marked 
with  a long  cut  of  a cold-chisel.  This  line-of-sight  mark  on 
muzzle  is  to  determine  the  position  of  the  reenforee-sight  in 
case  the  latter  should  be  knocked  away.  With  the  initial 
point  on  base-ring  and  mark  on  swell  of  muzzle,  thei-e  are 
two  points  available  for  determining  the  straight  line. 

1612.  In  case  a gun  slionld  be  received  rough-turned  at  its 
cylindrical  part  from  foundry,  and  it  should  become  necessaiy 
to  sight  the  gun,  the  breech  and  reenforce  sight-masses  will  be 
brought  down  to  a horizontal  plane  parallel  to  the  axis  of  the  bore 
as  follows  : the  straight-edge  will  be  laid  on  the  upper  side  of 
cylindrical  portion  of  breech,  and  brought  to  a level  with  the 
spirit-level.  The  mass  can  then  be  trimmed  down  to  this  plane. 

1613.  Instruments  %ised  in  sighting  a gun  : 

Trunnion-square.  Levelling-bar. 

Sighting-tompion  with  arm.  Steel  T-square  for  levelling  at 
Common  spirit-level.  muzzle. 


584 


NAVAL  ORDNANCE  AND  GDNNERT. 


Steel  straiglit-edge.  Beam  compasses  (witli  XY-inch 

Scribers.  gun.) 

Drills.  Tamplets. 

Steel  wedges  for  slot  of  lock-  Dividers, 
mass.  Ganges. 

1614.  Fitting  Side-sights. — This  is  considered  the  most 
difficult  kind  of  the  ordinary  sighting  of  guns,  and  requires  an 
experienced  mechanic.  First  level  the  gun  as  to  axis  of  bore 
and  trunnions  in  the  same  way  as  already  described.  Then 
determine  the  initial  point  on  base-ring  in  the  same  manner  as 
above.  This  point  w’as  probably  determined  when  the  gun  was 
central-sighted,  but  it  is  always  preferable  to  commence  anew, 
especially  when  the  central-sighting  was  done  by  some  other 
mechanic.  To  iix  the  position  of  the  rear-sight-box  on  the 
side  of  the  gun,  proceed  as  follows  ; 

1615.  First  to  determine  the  distance  that  the  sight,  EG 

(Fig.  344),  ought  to  be  in  rear  of  base-ring,  BR  : A standard 


distance  is  given  for  this,  measuring  from  base-ring.  Xow  to 
determine  the  distance  below  BIT  that  the  rear  sight  ought  to 
be.  Take  a small,  hard  piece  of  wood  of  a thickness  equal  to 
the  rim-base-sight  when  the  latter  is  finally  sci^ewed  into  rim- 
base.  Lay  this  piece  of  wood  on  rim-base.  Xext  take  a steel 
straight-edge  and  lay  it  with  its  edge  one  end  on  the  block  of 
wood  and  the  other  end  on  the  sight  fitted  to  the  box,  with  the 
shoulder  of  sight  resting  on  top  of  box.  The  end  of  the 
straight-edge  that  rests  on  the  notch  of  rear-sight  is  so  cut  away 
that  its  edge  fits  in  the  notch  neatly.  The  straight-edge  Ls  now 
levelled  by  moving  the  rear-sight-box  up  or  down.  When 
levelled  take  off  straight-edge  and  hold  rear-sight-box  firmly 
in  its  place  on  side  of  gun.  Take  out  the  rear-sight  from  its 
box  and  place  therein,  in  its  stead,  a steel  T-square,  the  longi- 
tudinal branch  of  which  is  round. 

1616.  The  T-square  being  in  the  rear-sight-box,  place  the 


SIGHTING  CANNON. 


585 


level  on  top  of  T-sqnare,  and  bring  the  box  itself  to  a level. 
This  of  course  will  require  the  slightest  possible  movement  of 
the  box,  as  when  the  straight-edge  was  on,  the  sight-box  was  ap- 
proximately adjusted.  The  rear-sight-box  being  levelled,  with- 
draw the  T-square  and  hold  the  box  firmly.  Then  mark  out 
its  place  on  the  gun,  and  also  the  places  of  its  holes  for  securing 
to  gun.  Bore  out  the  screw-holes  with  drill  and  tap  them. 
Fit  box  to  side  of  gnn  with  screws,  remembering  to  place 
rvhber  washei's  on  screws  between  the  gun  and  rear-sight-box. 
As  soon  as  the  box  is  fitted  to  gun  with  screws,  replace  its 
sight-bar,  and  again  go  through  the  operation  of  testing  the 
position  of  the  box  as  to  height,  by  placing  the  straight-edge  on 
block  of  wood  and  notch  of  sight  as  before.  Some  of  the 
screws  may  be  set  too  tight,  and  others  too  slack,  which  can  be 
remedied  before  proceeding. 

1617.  To  find  the  distance  of  the  rear-sight  from  the  axis 
of  the  bore,  place  the  steel  T-square  in  the  rear-sight-box  as 
before,  raising  it  until  it  touches  a straight-edge  resting  on  top 
of  rear-sight-mass,  and  crossing  the  gnn.  ISlow  measure  with 
accuracy  on  this  straight-edge  the  distance  from  the  initial 
point  established  on  base-ring  to  a point  on  top  of  T-square 
at  the  exact  intersection  of  its  longitudinal  and  transverse 
branches,  which  will  be  the  distance  required. 

1618.  To  fit  the  rim-base-sight  : Having  obtained  this  dis- 

tance, lay  it  off  on  the  horizontal  arm  of  a sighting-tompion. 


E 


Fig.  345. 


586 


NAVAL  OEDNANCE  AND  GIJNNEET. 


Tins  tompion  and  arm  are  to  be  placed  in  tlie  muzzle  as  repre- 
sented in  Fig.  345.  At  the  point  II  have  a centre-line  marked 
on  sigliting-arm,  and  wlien  the  arm  is  levelled  it  vrill  be  in  the 
same  vertical  plane  as  the  initial  point  already  established  on 
base-ring.  Now  take  the  distance  already  foimd  from  initial 
point  on  base-ring  to  point  on  T-square  when  in  rear-sight-bo.v, 
and  lay  it  off  on  horizontal  arm  of  tompion,  thus  establishing  a 
plane  parallel  to  axis  of  bore.  Take  the  thread  on  the  hori- 
zontal arm  at  this  point,  and  stretch  it  so  that  it  falls  on  the 
exact  centre  of  the  notch  of  rear  sight-bar,  and  mark  the  point 
where  it  touches  the  rim-base. 

1619.  The  distance  that  the  sights  shoidd  be  apart  is  fur- 
nished by  authority.  With  a straight-edge  mark  off  this  dis- 
tance, and  drill  a hole  for  rim -base-sight.  Then  counter-boi-e 
rim- base-sight.  As  soon  as  it  is  screwed  in,  lay  one  end  of  the 
straight-edge  on  it,  and  its  other  end  on  notch  of  breech-sight. 
Place  level  on  straight-edge.  Now  the  level  will  generally  be 
found  to  be  slightly  out,  and  it  can  be  brought  to  a level  by 
either  screwing  the  rim-base-sight  up  or  down  as  occasion  re- 
quires, or  by  cutting  down  the  notch-of-breech  sight  if  it 
should  want  to  be  lowered  at  that  end. 

1620.  For  side-sights,  the  breech-sight-bar  is  generally  sup- 
plied with  the  proper  firing  distances  marked  on  it.  Whenever 
a sight-bar  is  received  already  marked  Avith  ranges,  the  level 
should  never  be  remedied  by  cutting  away  the  shoulder  of  bar, 
as  the  edge  of  shoulder  is  the  initial  point  from  which  the  bar 
is  marked.  If,  however,  the  sight-bar  is  marked  after  it  is 
fitted  to  the  gun,  the  shoidder  can  be  thinned  down.  The 
levcllivg-bar  is  not  used  in  side-sighting  a gun. 

The  straight-edge  is  now  applied  as  before,  resting  on  rim- 
base-sight  and  notch  of  rear-sight-bar,  and  verified  as  to  the 
'level  of  that  plane.  If  the  spirit-level  remains  at  level,  the 
gun  is  properly  sighted  as  to  the  level  of  sights. 

1621.  Fittixg  Tnrxxiox’-siGHTS  to  Moetxes,  Grxs,  etc. — 
The  gun  is  first  levelled  as  to  axis  of  bore  and  axis  of  trunnions. 
Get  with  dividers  the  exact  centre  of  exterior  side  of  trunnion 
that  the  sight  is  to  be  fitted  to.  Drill  and  tap  hole  in  trunnion 
large  enough  to  receive  the  screw  of  “ stud  ’’  which  clamps  the 
sight  to  trunnion.  As  soon  as  this  hole  is  drilled,  screw  the 
“ trunnion-plate  ” to  trunnion.  Where  the  trunnion  is  not  of 
sufficient  length  to  admit  of  a trunnion-sight  Avithout  extension 
of  the  trunnion,  a “ trunnion-box  ” is  fitted,  AAdiich  prolongs  the 
trunnion  and  admits  of  the  sight  being  fitted  to  it.  The  “ trun- 
nion-plate ” being  screwed  on,  screw  in  the  “ stud ''  with  the 
“ heaver.”  Fit  the  trunnion-sight  on  this  stud  by  means  of  the 


SIGHTING  CANNON. 


587 


hole  through  sight  at  the  centre.  Place  washer  on  stud  and 
set  up  the  whole  with  “ wing-nut.”  Some  of  these  trunnion- 
sights  are  fitted  with  levels  in  them,  and  others  have  to  be  used 


NUT 

Fig.  346. 


in  connection  with  an  outside  level.  In  either  case  bring  the 
trunnion-sight  to  a level,  and  then  mark  on  the  trunnion-plate 
where  the  point  zero  degrees  of  trunnion-sight  comes.  Have 
this  point  for  a permanent  mark  on  trunnion.  (Art.  1G78.) 

1622.  Makking  Tangent-sights. — The  uppermost  line  on 
the  stem  marked  level  is  the  zero  of  the  other  graduations ; and 
when  adjusted  to  the  level  of  the  top  of  the  sight-box,  the  bot- 
tom of  the  notch  in  the  head  of  the  breech-sight  and  the  apex 
of  the  reenforce-sight  show  the  dispart  of  the  gun.  When  the 
line  of  sight  coincides  with  these  points  it  is  parallel  to  the  bore  ; 
and  when  continued  to  a distant  horizon,  the  gun  is  laid  level 
or  horizontal. 

Sights  should  invariably  be  made  so  that  the  level  line  on 
the  stem  will  correspond  with  the  bottom  of  the  head  ivhen  it 
rests  on  the  sight-box,  and  thus  secure  a dispart-sight  in  case  of 
accident  to  the  screw  in  sight-box. 

1623.  The  ranges  are  marked  in  even  hundreds  of  yards,  be- 
ginning with  100  yards,  and  marking  downwards  to  the  great- 
est range.  The  longer  lines,  representing  the  odd  hundreds,  have 
the  number  marked  upon  them  ; the  shorter  lines  not  marked, 
the  even  hundreds.  The  proper  time  of  fuze  is  also  marked 
for  the  corresponding  distance. 

These  sights  being  each  adjusted  to  a ^aarticular  gun,  and 
marked  with  its  class  and  number,  do  not,  in  strictness,  admit 
of  being  transferred  to  other  guns,  even  of  the  same  class.  The 
graduation  differs  for  each  class  of  guns  and  for  the  same  guns 
for  different  chai’ges. 


588 


NAVAL  OEDNANCE  AND  GUNNEET. 


1624.  When  used,  the  stem  of  the  breech-sight  must  be 
raised  or  lowered,  to  correspond  with  the  ascertained  or  esti- 
mated distance,  in  yards,  of  the  object  aimed  at,  and  firmly  se- 
cured there  by  the  thumb-screw.  Then,  if  the  ship  be  steady, 
elevate  or  depress  the  gun  until  the  line  of  sight  from  the  bot- 
tom of  the  notch  of  the  breech-sight,  the  top  of  the  reenforce- 
sight,  and  the  point  to  be  struck  will  coincide  ; but  if  the  ship 
have  a rolling  motion  the  gun  must  be  so  laid  after  the  sight  is 
set  for  the  distance,  that  this  coincidence  may  be  obtained,  if 
possible,  at  the  most  favorable  part  of  every  roll  which  the  ship 
makes. 

1625.  GRADTjATioif  FOR  DEGREES. — To  determine  the  grad- 
uation of  the  breech-sight  for  degrees  involves  the  solution  of 
a triangle  of  which  one  side  and  the  three  angles  are  known. 
Thus  in  the  figure  (347),  A is  the  position  of  the  front-sight,  A 


Fig.  347. 


A 


B is  the  distance  from  the  front-sight  to  the  rear  face  of  the 
breech-sight-bar  ; this  line  being  parallel  to  the  axis  of  the  bore, 
the  angle  B is  60°  ; the  problem  is  to  determine  the  length  of 
the  side  BC  for  all  the  values  given  to  the  angle  A. 

We  have 

sin  C : sin  A : : AB  : BC, 

„ AB  sin  A A o • A /-I 

BC= : — 7= — = AB.  sin  A cos  C. 

sin  C 

It  will  be  sufficiently  accurate,  after  having  determined  the 
value  of  BC  for  one  degree,  to  multiply  it  by  two,  three,  four, 
etc.,  in  order  to  determine  BC  for  these  different  values  of  A. 

It  is  evident  that,  for  the  same  value  of  A,  the  length  of 
the  side  BC  will  increase  with  the  length  of  the  side  AB; 
hence,  when  it  may  be  necessary  to  shift  the  front-sight  from 
the  reenforce  to  the  muzzle,  the  breech-sight  must  be  replaced 
by  another  graduated  in  proportion  to  the  increased  length  of 
the  side  AB.  (Art.  1592.) 

All  guns  fitted  with  a dispart-sight  on  the  top  of  the  piece 
near  the  trunnions  have  what  is  called  a clearance-angle. 

This  may  be  defined  as  the  angle  of  elevation  obtained  when 
the  top  of  tiie  tangent-scale  and  dispart-sight  and  the  notch  on 
the  muzzle  are  inline. 


DETEEMINING  DISTANCES. 


589 


If  the  scale  is  raised  above  this  angle,  the  dispart-sight  falls 
below  the  line,  joining  tlie  head  of  the  scale  and  the  muzzle. 

The  muzzle-notch  must  then  be  taken  as  the  second  point  of 
sight. 

1626.  Tables  of  Fike. — A properly  constructed  table  of 
fire  for  a particular  piece  contains  the  range  and  time  of  flight 
for  each  elevation,  charge  of  powder,  and  kind  of  projectile. 
Its  object  is  to  serve  as  a guide  in  pointing,  without  Avaste  of 
time  and  ammunition,  and  also  AAdien  the  effect  of  the  projectile 
cannot  bo  seen.  It  aids  in  securing  good  practice. 

The  Ordnance  Instructions  contain  approximate  range  ta- 
bles for  the  servuce  cannon. 

It  is  Avith  great  difficulty  that  tables  are  constructed  from 
the  results  of  the  most  careful  experiments,  owing  to  the  Amry 
different  ranges  and  deflections  obtained  in  firing  projectiles 
even  from  the  same  gun  with  similar  charges  and  elevations. 

It  must  be  remembered  that  any  practice  table  will  only 
serve  as  a general  guide,  and  that  small  alterations  in  .elevation 
or  deflection  are  required  according  to  the  force  and  direction 
of  the  Avind,  the  position  of  the  piece  Avith  respect  to  the  object, 
the  quality  of  the  poAvder,  and  several  other  circumstances. 

1627.  In  the  instruction  of  men  at  gun  practice,  the  inutility 
of  constantly  altering  the  elevation  to  correct  small  errors  in 
range  should  be  pointed  out,  and  the  necessity  of  observing  the 
I'esidts  of  several  rounds  Avithout  making  any  change,  so  as  to 
alloAV  for  the  necessary  probable  errors,  should  be  strongly  incul- 
cated, as,  under  the  most  favorable  circumstances,  Avith  smooth- 
bore ordnance  the  variation  of  range  is  found  to  equal  fifty 
yards  more  or  less. 

Errors  can  be  diminished  by  allowing  the  Gun  Captain  to 
estimate  the  distance  to  AvindAvard  or  leeAvard,  right  or  left,  to 
be  alloAved  for  the  deflection,  by  indicating  the  number  of  yards 
right  or  left  of  tlie  object ; Avhich,  after  all,  depends  on  his  es- 
timation of  distance,  or,  by  furnishing  a sight  Avhich  in  addition 
to  the  elevation  alloAvs  for  the  deviation,  and  permits  the  Gun 
Captain  in  all  cases  to  aim  directly  at  the  tai'get. 

Such  a sight  is  furnished  to  the  Parrott  rifle,  and  is  desirable 
for  all  guns.  (Art.  1593.1 

1623.  DETERMINIJS^G  DISTAE^CES.— In  all  circum- 
stances Avhere  ordnance  is  employed,  Avhether  in  the  field  or  on 
the  Avater,  a knowledge  of  the  distance  is  the  essential  element 
of  correct  practice. 

When  considerable,  it  is  usually  estimated  very  vaguely ; but 
the  necessity  of  knowing  it  as  correctly  as  possible  at  long 
ranges  is  greater  than  Avhen  the  trajectory  is  nearly  flat,  as  in 


590 


NAVAL  ORDNANCE  AND  GUNNERY. 


short  ranges ; elevation  being  given  according  to  the  distance, 
and  inaccuracy  increasing  with  length  of  range. 

At  considerable  distances,  also,  there  is  more  leisure  and 
opportunity,  as  well  as  greater  necessity  for  determining  those 
distances  vrith  precision,  while  in  closer  action  all  that  is  re- 
quired is  to  be  certain  that  the  enemy  is  within  range  at  level. 

Within  that  range,  if  the  hull  of  an  enemy’s  ship  is  ob- 
scured by  sjnoke  or  darkness,  the  aim  may  be  directed  by  the 
flash  of  liis  guns. 

1029.  Various  modes  have  been  practised  to  ascertain  at 
sea  the  distance  from  the  object  aimed  at,  so  as  to  regulate  the 
elevation  of  guns,  hut  none  can  he  depended  upon  for  giving  it 
Avith  minute  accuracy,  aiid  even  when  obtained,  it  is  continually 
varying ; therefore,  Avhen  the  projectile  is  seen  to  exceed  or 
fall  short  of  the  object  considerably,  the  sight-bar  must  be  re- 
adjusted accordingly.  It  tliTis  becomes,  under  ordinary  cir- 
cumstances, a good  instrument  for  approximating  distances. 

The  con-ection  of  the  tire  by  previous  rounds  is  a practical 
means  which  is  much  resorted  to  on  all  occasions,  but  it  is 
hardly  to  be  relied  on  when  the  observer  is  near  the  piece 
flred. 

In  departing  from  the  line  of  fire,  however,  the  means  of 
noticing  correctly  the  errors  of  range  increase.  Vessels  in 
line,  therefore,  can  easily  amend  their  elevation  of  gun  and 
time  of  fuze  by  the  signals  of  those  most  remote  from  them. 

Officers  of  divisions  and  Gun  Captains  should  be  occasion- 
ally practised  in  measuring  the  distances  of  objects  by  the  eye, 
at  times  when  opportunities  offer,  of  verifying  the  accuracy  of 
their  estimates,  by  comparing  it  with  the  distance  obtained  by 
measurement,  or  by  any  other  method  Avhich  will  aftord  the 
best  means  of  comparison. 

1630.  Angle  subtended  by  the  Mast  of  the  Enexcy. — 
Among  other  methods  of  estimating  distances  is  that  of  making 
use  of  the  different  angles  subtended  at  different  distances  by 
the  heights,  when  known,  of  the  masts  of  the  ships  avliose  dis- 
tance is  desired.  The  heights  and  distances  being  arranged  in  a 
table  so  that  by  simply  measuring  with  a sextant  the  angular 
height  of  the  mast, — as  is  commonly  done  in  chasing,  to  ascer- 
tain whether  the  chase  be  gaining  or  losing  distance — and  en- 
tering the  column  of  angles,  the  corresponding  distance  may 
be  tiucen  out.  In  the  old  editions  of  the  Ordnance  Instruc- 
tions, tables  Avere  inserted  in  which  the  distances  corresponding 
to  different  angles  subtended  by  the  masts  of  English  and 
Erencli  vessels  were  given,  and  the  sights  might  be  regulated 
•accordingly,  if  circumstances  should  requme  it. 


DETERMIXrXG  DIST.\ITCES. 


591 


1631.  Hoeizoxtai,  Angles  taken  at  Bow  and  Steen. — An- 
other method  which  has  been  recommended  consists  in  taking 
simnltaneonsly  at  the  how  and  stern  of  the  ship  the  horizontal 
angles  between  the  lines  joining  the  stations  of  the  observers 
and  lines  drawn  from  those  stations  to  the  object.  This  method 
requires  a favorable  position  of  the  object. 

1632.  Using  Ship’s  own  Mast  as  the  Given  PIeight. — The 
distance  may  be  determined  bv  making  use  of  the  ship’s  own 
mast  as  a given  height,  causing  an  observer  aloft  to  measm’e 
the  angle  formed  by  the  mast  when  vertical  and  the  line  of 
sight  from  the  observer  to  the  object,  and  then  computing  the 
required  horizontal  distances. 

Another  application  in  an  oblique  plane  of  the  horizontal 
method  is  to  let  two  observers,  each  visible  from  the  other,  take 
their  stations  at  the  ends  of  a rope  whose  length  is  accurately 
measimed,  and  simultaneously  measure  the  angle  between  the 
other  observer  and  the  object ; tlie  three  angles  and  one  side  of 
a triangle  are  thus  obtained,  and  the  side  wanted  can  be  readily 
calculated.  Take,  for  instance,  one  observer  at  the  main  top- 
mast cross-trees  and  the  other  in  the  main-chains,  the  main  top- 
mast back-stay  will  answer  for  a base. 

1633.  Bucknee’s  Method. — To  determine  the  distance  of 
an  object  at  sea  by  observing  its  angular  distance  from  (within) 
the  oiling. 

This  is  done  as  follows  : 

In  the  tigm’e  (318)  let  OB  represent  the  sea-level ; A,  the 


position  of  the  observer  at  the  height,  AB,  above  it ; AC,  a hor- 
izontal line  and  parallel  to  it ; O,  the  offing,  or  edge  of  the  visi- 
ble horizon ; K,  the  object  whose  distance  is  required  : 

We  have  CAO  ==  dip.  Bowditch  Table  XIII. 

OAK  = angular  distance  of  K within  the  offing. 
Hence  we  have 

KAB  = CAB  - (CAO  + OAK), 

KAB  90°  - (CAO  + OAK), 

AB  =r  height  of  observer. 


592 


NAVAL  ORDNANCE  AND  GUNNERY. 


Hence,  in  the  right-triangle  KAB,  we  know  the  angle  A 
and  the  side  AB. 

We  may  find  KB  from  the  formrda 

* KB 

KB  = AB  tan  A. 

Ko  correct  nse  can  he  made  of  this  method  when  the  prox- 
imity of  land  interferes  with  the  distance  of  the  horizon. 

The  corrections  for  curvature  of  the  earth  and  teiTestrial 
refractions,  being  slight,  are  neglected. 

In  the  Ordnance  Instructions  there  is  a table  for  finding  the 
distance  of  an  object  at  sea  computed  by  this  formula,  KB  be- 
ing taken  for  every  1 00  yards  and  the  angle  A calculated  for 
the  height  of  20,  30,  40,  etc.,  feet. 

To  use  the  table  let  an  observer  from  the  cross-trees  or  any 
other  station  measure  the  angle  between  the  distant  horizon  and 
the  object,  and  look  into  the  table  with  that  angle;  opposite  to 
it,  in  the  column  marked  “Distances  ” will  be  found  the  distance 
of  the  object  in  yards. 

1634.  By  the  Velocity  of  Sound. — To  estimate  the  distance 
by  the  bursting  of  shell,  when  the  flash  can  be  seen,  multiply 
the  number  of  seconds  which  elapse  between  it  and  the  sound 
of  the  re].iort  by  HOC,  and  the  product  will  be  nearly  the  dis- 
tance in  feet.  (Art.  1696.) 

1635.  By  the  TnuEE-POiXT  Pkoblem. — It  is  sometimes  con- 
venient, when  at  anchor,  and  the  object  is  fixed,  to  measure 
with  a sextant  the  horizontal  angles  between  any  three  points 
conveniently  located,  and  whose  positions  are  accurately  laid 
down  on  the  chart,  then  plotting  the  angles  or  working  them 
out ; or  a base-line  can  be  taken  between  the  vessels  at  anchor, 
or  measured  on  shore,  then,  by  angling  on  the  object  to  be  aimed 
at,  the  distance  can  be  calculated. 

1636.  The  Militaky  Telemeter,  represented  by  Fig. 
348-J^,  is  the  invention  of  Major  P.  Le  Boulengc,  of  the 
Belgian  Army.  The  want  of  some  method  of  measuring  the 
distance  has  not  been  satisfactorily  supplied,  for  the  reason  that 
i\\Q  telemeters  hitherto  proposed  all  depend  upon  more  or  less 
simplified  processes  of  triangidation  ; and  none  of  these  instru- 
ments have  been  generally  adopted. 

This  instrument  measures  the  distance  by  obseiwing  the  in- 
terval which  elapses  between  the  smoke  or  flash  and  the  report 
of  fire. 

It  is  a glass  tube  graduated  along  its  length  into  divisions 
which  represent  distances.  This  tube,  closed  at  both  ends,  is 


DETERmXING  DIST.^’CES. 


593 


filled  Avitli  liquid,  througli  Tvhich  moves  a metal  index  formed  of 
two  disks  united  by  a central  stem.  The  diameter  of  these  disks 
is  somewhat  smaller  than  that  of  the  tube,  so  that,  when  the  lat- 
ter is  vertical,  the  index  slowly  descends  with  a uniform  move- 
ment. The  glass  is  protected  by  a brass  easing  having  an  aper- 
ture which  discloses  the  scale  and  index. 


Fig.  348i. 


To  use  the  telemeter,  hold  it  horizontally  in  the  hand,  the  in- 
dex at  the  origin  of  the  scale,  and  attentively  regard  the  enemy’s 
position.  At  tlie  instant  the  smoke  or  flash  is  perceived  quickly 
turn  the  wrist  so  as  to  bring  the  instrument  into  the  vertical, 
when  the  index  descends  ; upon  hearing  the  report  return  it  to 
the  horizontal  by  the  inverse  movement  of  the  wrist,  and  the  in- 
dex ’stops.  The  number  on  the  scale  corresponding  to  the  lower 
disk,  Avhich  serves  as  marker,  is  the  distance  sought. 

This  very  simple  chronometric  device  is  characterized  by  a 
uniform  movement  and  works  with  extreme  precision.  Hence, 
knowing  the  velocity  of  sound  and  that  of  the  index,  it  is  easy  to 
graduate  the  scale  into  divisions  which  exactly  represent  dis- 
tances. 

An  important  attribute,  which  has  been  successfully  given  the 
instrument,  is  its  power  of  self-adjustment  for  temperature.  To 
effect  this  tlie  volume  and  density  of  the  index  and  the  density 
and  dilatability  of  the  liquid  are  so  combined  that  tlie  velocity  of 
the  index  is  influenced  by  temperature  in  the  same  proportion  as 
is  the  velocity  of  sound ; consequently  the  readings  are  always 
correct. 

A velocity  1-25000  that  of  sound  has  been  adopted  for  the 
index,  so  that  a millimetre  on  the  scale  represents  twenty-five 
metres  of  distance.  Each  degree  of  the  scale  rejiresents  twenty- 
five  metres,  and  with  the  eye  the  fifth  of  a division  can  be  es- 
timated. 

When  proved  by  vibrations  of  a pendulum  or  the  beats  of  a 
watch,  this  telemeter  is  absolutely  true,  while  the  exactness  of 
38 


694 


NAVAL  ORDNANCE  AND  GUNNERY. 


its  indications  in  measuring  distances  depends  upon  tlio  aptness 
of  the  observer. 

From  the  results  obtained,  the  following  conclusions  may  1je 
drawn : the  accidental  error  committed  by  the  ordinary  ob- 
server does  not  generally  exceed  fifty  metres ; with  practice  this 
is  diminished  to  twenty  or  twenty-five  metres.  Every  one  has 
his  own  personal  equation,  and  this  should  be  known  to  derive 
all  possible  adv^antage  from  the  instrument ; though  it  varies 
little  among  observers,  and  on  the  average  lessens  the  distance 
fifty  metres,  the  report  being  noted  more  quickly  than  the  flash 
or  smoke.  This  mean  equation  is  corrected  on  the  instrument 
itself  by  making  the  origin  of  the  scale  corresj)ond  not  to  zero 
but  to  fifty  metres.  It  is  an  advantage  always  to  use  the  same 
telemeter  in  order  to  iinite  in  the  personal  equation  the  slight 
error  which  may  exist  in  the  graduation.  An  observer  is  liable  to 
commit  very  great  errors  in  his  first  attempts,  because,  unac- 
customed to  the  duty,  he  is  surprised  by  the  flash  or  smoke  and 
does  not  promptly  note  it.  The  error  is  independent  of  the  dis- 
tance, hence  the  personal  equation  decreases  slightly  with  the 
distance.  The  fire  of  small-arms  may  be  observed  as  exactly  as 
that  of  artillery  up  to  two  thousand  metres  in  favorable  weather. 
The  wind  appears  to  have  very  little  influence  upon  the  obser- 
vation ; this,  however,  has  not  yet  been  fully  proved. 

1G37.  Plane-tables  may  be  used  on  shore  to  determine 


distances  and  to  note  the  fall  of  projectiles  in  target  practice  or 
firing  for  ranges.  An  ordinary  plaue-table  (Fig.  349)  is  a tripod 


DETEEMIITIJTG  DISTANCES, 


595 


simnounted  by  a drawing-board  covered  with  paper.  To  be 
nsed  in  connection  with  it  is  an  alidade  for  observing  and  mark- 
ing the  ranges. 

This  is  a flat  metallic  ruler,  resting  and  moving  on  the  sur- 
face of  the  paper  and  carrying  upon  it  a light  upright  column, 
at  the  head  of  which  is  another  ruler  having  a vertical  move- 
ment only ; its  extreme  points  are  fitted  with  raised  sights  (a 
notch  and  a point)  which  collimate  with  the  bevelled  edge  of 
the  lower  ruler.  At  one  end  of  the  lower  ruler  is  an  extension 
of  the  metal  perforated  to  receive  the  head  of  a pin  the  centre 
of  which  is  to  concide  with  the  bevelled  edge  of  this  horizontal 
ruler. 

Near  one  of  the  corners  of  the  plane-table,  a small  brass 
plate  is  counter-sunk  in  the  wood  and  tapped,  so  as  to  receive  a 
pin  about  half  an  inch  long  and  screw-cut,  having  a milled-head 
above  which  is  a continuation  of  the  pin  two-tenths  of  an  inch 
in  length,  turned  perfectly  smooth  so  as  to  permit  the  rule  to 
pivot  about  it  as  a centre. 

1638.  If  the  target  is  on  the  water,  a point  along  the  shore, 
the  distance  of  which  from  the  battery  has  been  ascertained,  is 
selected  so  that  a line  drawn  from . it  towards  the  place  where 
the  first  grazes  are  expected  to  occur  will  be  at  right  angles  to 
the  line  of  fire,  or  nearly  so : here,  one  of  the  plane-tables  is 
placed.  The  other  is  sitnated  as  nearly  in  line  with  the  target 
and  battery  as  convenient ; sufficiently  removed,  however,  not 
to  be  inconvenienced  by  the  smoke.  The  two  stations  should 
be  so  situated  that  lines  drawn  from  them  to  the  target  will  be 
nearly  at  right-angles  to  each  other. 

Their  distances  from  each  other  and  from  the  batteiy  are 
known. 

The  table  is  adjusted  with  the  small  metal  plate  over  the 
stake  that  marks  the  station,  and  levelled. 

The  observer  places  his  alidade  on  the  pivot-pin,  sights 
carefully  on  a given  point  at  the  battery,  and  marks  on  the 
paper  affixed  to  the  table  the  direction  assigned  by  the  bevelled 
edge  of  the  ruler.  The  direction  of  the  other  station  is  noted 
in  the  same  way,  as  is  also  the  target  and  any  stakes  which 
may  be  placed  in  the  line  of  fire. 

When  the  cannon  is  ready  to  fire,  a preparatoiy  signal  is 
hoisted  at  the  battery ; seeing  this,  the  observer  points  the 
alidade  in  the  expected  direction  of  the  first  graze. 

The  signal  is  lowered  and  the  gun  fired.  The  instant  the 
jet  takes  place,  the  sights  of  the  alidade  are  aligned  upon  it, 
and  the  direction  indicated  by  the  bevelled  edge  of  the  rulei 
marked  upon  the  paper. 


596 


NAVAL  OKDNANCE  AND  GUNNERY. 


The  line  connecting  the  two  stations  is  a base  from  which 
is  determined  the  position  of  the  point  struck  and  of  the  batteiy. 
The  projection  of  this  base  on  any  scale  will  enable  one  to  aV 
certain  in  terms  of  that  scale  the  distances  desired. 

After  the  firing,  the  tables  are  returned,  the  obseiwations 
made  on  one  table  transferred  to  the  other,  and  the  intersec- 
tions of  the  lines  locate  the  positions  of  the  points  struck. 

1639.  Dangeeotjs  Space. — If  the  object  tired  at  be  wide  but 
of  small  depth,  the  deflections,  unless  very  great,  will  be  of 
small  importance  so  long  as  the  ranges  are  regular  : shoidd  the 
object  be  deep  and  only  present  a narrow  front,  uniformity  in 
range  will  be  of  little  importance  when  the  deflections  vary 
considerably. 

The  range  varies  with  the  angle  of  Are  and  the  initial  ve- 
locity, and  depends  at  the  same  time  upon  the  diameter  and 
density  of  the  projectile.  The  greater  the  velocity,  the  flatter 
the  trajectory,  and  consecjuently  the  greater  the  chance  of  the 
object  intercepting  the  projectile,  and,  also,  the  longer  the  ex- 
tent of  ground  covered  by  the  projectile,  or  the  dangerous 
sj>ace,  making  the  practice  more  accurate. 

1610.  ACCURACY  OF  FIRE. — Firing  for  accuracy, 
whether  with  artillery  or  small-arms,  may  involve  two  entirely 
separate  and  distinct  things  ; 

1st.  The  determination  of  the  personal  skill  of  the  individ- 
ual using  the  weapon. 

2d.  The  determination  of  the  qualities  as  regards  accuracy 
of  the  weapon  itself. 

The  most  common  way  of  determining  the  relative  accu- 
racy of  guns  is  to  ascertain  their  mean  differences  of  range  and 
mean  reduced  deflection  for  a given  mean  range,  and  compare 
them — that  gun  being  the  most  accurate  for  which  these  quan- 
tities are  smallest. 

1641.  2Iean  Range. — The  mean  range  is  found  by  adding 
all  the  ranges  together,  and  dividing  the  sum  by  the  number  of 
shots  fired. 

1642.  Mean  Difference  of  Range,  or  the  mean  error  in  range, 
may  be  found  by  taking  the  difference  between  each  range  nnd 
the  mean  range : add  the  differences  together,  divide  by  the 
number  of  shots  fired,  and  the  quotient  will  be  the  mean  differ- 
ence of  range. 

1643.  Mean  Deflection.— KA2  together  separately  all  the 
right  deflections  and  all  the  left  deflections ; subtract  the 
smaller  sum  from  the  larger,  and  divide  the  difference  by  the 
niunber  of  shots  flred ; the  result  will  be  the  mean  deflection. 

1644.  Mean  reduced  Deflection,  or  the  mean  error  in  di- 


ACCURACY  OF  FIRE. 


597 


rectiun,  is  found  by  taking  the  distance  of  each  deflection  from 
a line  passing  through  the  mean  deflection  add  these  distances, 
termed  reduced  deflections,  together,  and  divide  by  the  number 
of  shot  tired,  for  the  mean  reduced  deflection. 

16i5.  Example. — Five  shot  fired  under  similar  circum- 
stances give  the  following  ranges  and  deflections  : 


Ranges.  reflections. 

■yards.  Yards. 

lUlO 4— Right. 

1060 1—  “ 

1010 2 — Left. 

1020 5—  “ 

1030 S — Right. 

O 


Sum  of  ranges  5160  , 

Number  ot  shot  hred  o j ^ a 

Tlie  differences  between  each  range  and  the  mean  range  are 
22,  28,  8,  12,  and  2 = 72  yards. 

11.1  yds.,  mean  difference  of  range. 

Sum  of  right  deflections  = 8 yards. 

Sum  of  left  deflections  = 7 “ 

Difference  = 1 “ 

^ 0.2  yards,  right  mean  deflection. 

Deflections  from  line  through  mean  deflection : 3.8,  8,  2.2, 

5.2,  and  2.8  = 14.8. 

11  8 

— — = 2.96  yds.,  mean  reduced  deflection. 

1616.  An  exact  definition  of  the  accuracy  of  a gun  is  a 
matter  of  no  little  difficulty.  Of  two  guns  fired  from  the  same 
place,  the  same  number  of  rounds,  at  the  same  target,  Avith 
their  axis  in  the  same  dh’ection,  that  would  evidently  be  the 
more  accurate  which  planted  its  shot  more  nearly  together. 
But  it  is  not  always  possible  to  test  the  practice  of  guns  under 
precisely  similar  circumstances  ; therefore  Ave  must  seek  a defi- 
nition equally  true,  but  admitting,  in  addition,  more  elasticity 
in  its  application. 

Upon  reflection,  it  becomes  evident  that  an  absolutely  accu- 
rate gnu  is  one  Avith  Avhich,  tired  under  identical  circumstances, 
the  chance  or  probability  of  striking  the  same  spot  twice 
amounts  to  certainty.  Adopting  the  mathematical  notion  of 
probability,  this  Aviil  be  represented  by  unity — guns  less  accu- 
rate having  probabilities  represented  by  fractions.  Such  a 
mode,  though  suggested,  has  not  been  accompanied  by  the  req- 
uisite tables  to  render  it  of  general  use. 


598 


NAVAL  OEDNANCB  AND  GUNNERY. 


1647.  It  is  easier  to  determine,  from  tlie  practice  of  the  gun 
itself  a rectangle  with  which  there  would  be  an  equal  chance  of 
any  shot  from  the  gun  striking  or  not  striking  ; or,  if  a given 
number  of  shots  were  fired,  half  the  mmiber  might  be  expected 
to  fall  within  the  area. 

The  accuracies  of  two  guns  would  be  inversely  as  these 
rectangles  for  the  same  range.  This  method  was  proposed  bv 
Captain  Koble,  E..  A.,  who  furnished  the  following  formula  for 
application.  If  a be  the  length,  and  h the  width  of  the  area  or 
rectangle  required,  then 

sum  of  differences  of  ranges. 

ft  = 3.12  X .84.o3, ^ -j  j 7 

one  less  than  number  of  ranges 

7 0 7 Ko  sum  of  reduced  deflections. 

b — 3.12  X .8453, ; ^ , ^ 

one  less  than  number  ot  detiections 

1648.  Accukacy  of  Small-aejis. — The  I’elative  precision  of 
small-arms  is  decided  by  various  methods. 

Centre  of  Impact.— T\iq  point  of  impact  of  a ball  is  the 
point  where  it  strikes  the  target,  and  the  mean  of  all  the  hits 
is  called  the  mean 'point  of  impact.,  or  the  centre  of  impact. 

To  determine  this  point,  let  the  piece  be  pointed  at  the  cen- 
tre of  a target  stationed  at  the  required  distance,  and  fired  a 
certain  number  of  times,  and  let  the  positions  of  the  shot-holes, 
measured  in  vertical  and  horizontal  directions  from  the  lower 
left-hand  corner  of  the  target,  be  arranged  as  in  the  following 

0^0  o 

table  ; 


No. 

of 

shot. 

Distances  from  lower  left-hand 

comer  in  feet. 

Above. 

Right. 

1 

9 

10 

2 

0 

4 

3 

5 

8 

S')  14 

S')  22 

4.U7 

7.3S 

The  sum  of  all  the  vertical  distances  dixdded  by  the  number 
of  shots  gives  the  height  of  the  centre  of  impact  above  the 
origin. 


ACCURACY  OP  FIRE. 


699 


Similarly  tlie  sum  of  all  the  horizontal  distances  divided  by 
the  number  of  shots  gives  the  horizontal  distance  from  the 
origin  to  the  centre  of  impact. 

Thus  from  the  above  table  the  co-ordinates  of  the  centre  of 
impact  are  4.G7  and  7.33.  The  co-ordinates  of  the  centre  of 
the  target  being  6 each,  the  centre  of  impact  is  1.33  below  and 
1.33  to  the  right  of  the  centre  of  the  target. 

1649.  Absolute  Mean  Deviation. — The  co-ordinates  of 
the  centre  of  impact  being  known,  the  point  itself  is  known, 
and  its  distance  from  the  centre  of  the  target  is  called  the  ahso- 
lute  mean  deviation.  This  is  equal  to  the  square-root  of  the 
sum  of  the  squares  of  its  vertical  and  horizontal  distances  from 
the  centre  of  the  target. 

1650.  Mean  Deviation. — To  obtain  the  mean  deviation  it 
is  necessary  to  refer  each  shot-hole  to  the  centre  of  impact  as  a 
new  origin  of  co-ordinates,  and  this  is  done  by  taking  the  differ- 
ences between  each  tabular  distance  and  the  distance  of  the 
centre  of  impact  and  adding  them.  The  sum  of  all  the  dis- 
tances thus  obtained  in  one  direction  divided  by  the  number  of 
shots  gives  the  mean  deviation  oy  figure  of  merit. 

A shorter  rule  may  be  found : for  if  there  ai-e  m distances 
greater,  and  n distances  less  than  the  distance  from  the  origin 
to  the  centre  of  impact,  calling  a the  sum  of  the  greater  and 
& the  sum  of  the  less,  we  may  write 


In  using  this  formula,  due  care  must  be  paid  to  the  sign  of 
(w  — m). 

This  method  might  be  applied  to  the  fire  of  cannon  by  re- 
ducing the  grazes  to  an  imaginary  vertical  target,  the  angles  of 
descent  being  assumed  equal  for  all  shot  fired  at  the  same 
elevation. 

Applying  this  formula  to  the  table  given  above,  we  get 
3.11  feet  vertically,  2.22  feet  horizontally  for  the  mean  devia- 
tion OY  figure  of  merit. 

1651.  Mean  Horizontal  and  Mean  Yertical  Error. — 
The  mean  horizontal  error  is  found  by  adding  the  horizontal 
distances  by  which  the  balls  have  missed  the  centre  of  the 
target,  and  dividing  this  sum  by  the  number  of  balls  ; this 
quotient  indicates  how  much  the  average  of  the  balls  have 
missed  horizontally  the  point  aimed  at. 

It  may  be  directly  and  readily  found  by  using  the  formula 
of  the  preceding  article,  substituting  for  ~x  the  horizontal  dis- 
tance of  the  centre  of  the  target  from  the  origin. 


a — mx-\-nx—h 
m 4-  n 


a — T)  {n  — m)  X 


m -f-  n 


= figure  of  merit. 


600  I NAVAL  ORDNANCE  AND  GUNNERY. 

Similarly  the  mean  vertical  error  may  he  found,  by  using  the 
same  formula,  with  the  substitution  for  ~x  of  the  height  of  the 
centre  of  the  target  above  the  origin.  The  result  shows  evidently 
by  how  much  the  average  of  the  shots  have  missed  vertically. 

1662.  The  Absolute  Mean  Ekeor. — To  get  this,  there  are 
two  methods.  The  first  is  short  and  simple,  and  consists  in  cal- 
culating the  hypothenuse  of  a right  triangle,  in  which  the  other 
two  sides  are  the  mean  horizontal  and  mean  vertical  errors. 

The  second,  which  should  be  called  the  calculation  of  the 
meam,  of  the  absolute  errors^  consists  in  measuring  for  each  ball 
its  absolute  error,  a distance  from  the  point  aimed  at,  and  to 
take  the  mean  of  these  absolute  errors  by  dividing  then’  sum  by 
the  number  of  balls  fired. 

This  method  is  very  long,  since  to  have  the  absolute  error 
of  each  ball  it  is  necessary  to  square  two  numbers  and  then 
extract  the  square-root  of  these  sums  as  the  distance  of  the 
points  struck  have  been  measmed  upon  the  vertical  and  hori- 
zontal lines  passing  through  the  point  aimed  at. 

The  results  are  not  exactly  the  same  ; the  mean  of  the  abso- 
lute errors  will  be  greater  than  the  absolute  mean  error. 

1653.  Radius  of  a Circle  Containing  a Fraction  of  the 
Balls. — The  radius  of  a circle  containing  a fraction  of  the 
balls,  the  third,  half,  or  two-thirds  is  a common  test  of  accuracy. 
Its  centre  is  the  point  aimed  at ; its  radius  is  the  absolute  error 
of  the  third,  half,  or  two-thirds  of  the  other  absolute  errors 
arranged  in  order  of  size.  Thus:  3,  4,  6,  7,  9,  15,  IS,  21.  25, 
being  the  order  in  size  of  the  absolute  errors  of  nine  balls. 
6 will  then  be  the  radius  of  the  circle  containing  the  thi/'d  of 
the  best  shots,  9 that  containing  the  best  half,  and  IS  that 
containing  the  best  two-thirds.  If  the  number  of  balls  fired 
be  even,  the  circumference  of  the  circle  should  pass  equally 
distant  from  the  two  balls  which  limit  it. 

For  example,  if  we  have  twelve  balls,  and  wish  the  circle 
containing  the  best  third,\hG  circumference  should  pass  between 
the  fourth  and  fifth  balls  at  equal  distances,  the  fourth  within 
and  the  fifth  without.  If  the  number  of  balls  be  uneven.  9 
for  example,  and  we  want  the  circle  containing  the  best  half  of 
them,  we  pass  it  through  the  centre  of  the  fifth  ball. 

1654.  The  Pee  cent.— This  test  of  accuracy  indicates  how 
many  of  one  hundred  balls  fired  have  hit  the  target.  To  get 
the  per  cent.,  count  the  number  of  balls.  A,  that  have  hit  the 
target,  of  the  number,  B,  that  have  been  fired,  and  from  the 
proportion  B ; a : : 100  : x.,  we  have  the  per  cent., 

JOO  X a 


ACCURACY  OF  FIRE. 


601 


1655.  CoiiPAKisoN  OF  THE  DiFFEEENT  Methods. — The  de- 
termination of  the  mean  point  of  impact  can  only  he  nsed  in 
comparing  tlie  accuracy  of  two  pieces  that  are  of  tlie  same 
model  and  fired  nnder  precisely  the  same  conditions;  thus  in 
general  the  mean  point  of  impact  gives  only  an  imperfect  idea 
of  the  accuracy  of  a piece.  The  mean  horizontal  error  indi- 
cates only  that  the  greatest  nnmher  of  halls  have  gone  too  far 
to  the  right  or  left.  Moreover,  it  may  occur  that  two  pieces 
have  the  same  horizontal  error,  while  the  mean  vertical  error 
will  he  very  different. 

The  radius  of  a circle  containing  a fraction  of  the  halls  can- 
not  give  a perfect  idea  of  the  accuracy  of  a piece  unless  the 
halls  are  placed  progressively  distant,  which  cannot  reasonahly 
he  expected. 

The  Per  Cent. — If  a piece  he  fired  that  has  many  causes  of 
error,  and  we  wish  to  test  the  skill  of  the  marksman  or  the 
accuracy  of  the  arm,  only  to  the  extent  of  ascertaining  how 
many  halls  can  he  placed  in  the  target,  this  method  is  simple 
and  sufficiently  exact.  The  surface  covered  hy  the  halls  should, 
however,  he  taken  into  account,  for  it  may  occxir  that  with  one 
arm  the  halls  are  scattered  over  the  entire  target,  while  with 
the  other  they  are  grouped  in  a small  space ; this  latter  piece 
would  he  the  more  accurate. 

It  would  appear,  then,  that  the  method  of  the  absolute  mean 
error  should  he  preferred : for  it  represents  a quantity  the 
ratio  of  which  to  the  accuracy  of  the  piece  the  mind  can 
readily  perceive ; and  this  quantity  depending  upon  the  posi- 
tion of  each  one  of  the  halls  varies  when  one  of  them  varies, 
and  thus  gives  a clear  idea  of  the  accuracy  of  the  piece. 

1650.  The  Inclination  of  the  Target. — The  most  com- 
mon modes  of  recording  target-practice  are : rerticalVp  as  for 
smaU-arms,  and  horizontaThj  as  for  great  guns. 


Slight  vertical  errors  on  a vertical  target  are  magnified  into 
large  errors  in  range,  while  the  deviations  are  unchanged. 
Doubtless  the  fairest  position  of  the  target  is  that  which  would 


602 


NAVAL  ORDNANCE  AND  GUN'N’ERT. 


receive  the  projectile  at  light  angles  to  its  own  surface ; for 
witli  this  a normal  target,  there  will  be  no  distortion  of  errors 
either  in  favor  of  or  against  the  gun. 

There  is  no  real  objection  to  anj  of  these  positions  of  the 
target,  as  points  on  one  can  be  transferred  to  each  of  the  other 
two  with  facility,  using  the  angles  of  fall  from  Bvclcner’s 
Tables,  and  assuming  that  the  path  of  the  projectile  from  the 
vertical  target  to  the  ground  is  a straight  line. 

From  an  inspection  of  Fig.  354,  it  is  seen  that  error  on  ver- 
tical target  (Be)  error  on  horizontal  target  (Ac)  X tan  A . . . (1) 

Error  on  normal  target  (cD)  = error  on  horizontal  target 
(Ac)  X sin  A (^2). 

If  A,  the  angle  of  fall,  be  very  small,  there  will  be  no  apprecia- 
ble difference  between  its  sine  and  tangent,  and  the  vertical  and 
normal  targets  will  virtually  coincide.  If  A be  large,  however, 
all  determinations  of  the  accuracy  of  the  guns  should  strictly 
be  made  upon  the  normal  target. 

1657.  Kecokd  of  Taeget-pkactice  at  Sea. — The  record  of 
a target-practice  with  great-guns  should  give  for  each  shot  the 
calibre  and  class  of  the  gun,  the  weight  of  the  charge,  the 
nature  of  the  projectile;  if  a shell,  whether  it  biu’st  before  or 
after  striking  the  water,  or  not  at  all,  the  observed  distance  of 
the  target,  the  observed  error  in  range,  observed  or  estimated 
deviation,  and  the  distance  for  which  the  sight  was  set.  In  the 
record  should  also  appear  the  character  of  the  wind  and  the 
sea,  the  motion  of  the  ship,  and  the  circumstances,  so  far 
as  can  be  ascertained,  attending  any  special  occurrence. 

1658.  The  following  method  of  keeping  the  record  is  based 
upon  suggestions  by  Capt.  Jeffers,  U.  S.  N. : 

An  officer  and  a recorder  are  stationed  at  the  topmast  cross- 
trees.  The  former  takes  frequently  the  angles  betiveen  the 
sea  horizon  and  the  target,  and  gives  them  to  the  FTavigator, 
who  looks  out  the  corresponding  distances  and  reports  them  to 
the  executive  officer.  The  officer  aloft  also  takes  the  angles 
between  the  horizon  and  each  point  of  impact. 

The  recorder  enters  on  a ruled  form  all  the  angles  in  suc- 
cession, denoting  target  angles  by  a check.  He  also  has  a 
paper  divided  into  quarters  by  two  lines  at  right  angles  to  each 
other  through  the  centre  of  the  page.  lYhenever  a shot  is 
fired,  he  notes  in  the  appropriate  quadrant  the  number  of  the 
shot ; his  own  estimation  of  the  distance  short,  over,  right,  or 
left ; and  the  bursting  of  the  shell  as  either  before  or  after  im- 
pact. 

Thus  the  diagram  (Fig.  351)  indicates  that  the  fifth  shell  in 
the  order  of  firing  burst  before  impact,  and  the  pieces  struck 


ACCURACY  OF  FIRE. 


603 


ten  yards  short  and  fifteen  to  the  left ; also  that  the  seventh 
struck  thirty  yards  over  and  five  to  the  right,  bursting  after  im- 
pact. Ricochet  hits  are  marked  by  an  R. 

An  observer  furnished  with  a similarly  ruled  paper,  and 
stationed  forward  or  aft, 
depending  upon  the  wind, 
keeps  an  independent  record 
of  his  estimation  of  the  fall 
of  the  projectile  and  the  ex- 
plosion of  the  sliell  as  a 
cheek  upon  the  fi)’st  I'ecorder. 

A competent  person  on 
the  gun-deck  records  the 
number  of  the  guns  in  their 
order  of  firing,  and  the  dis- 
tances for  which  the  sights 
were  set. 

The  clerk  notes  the  time  when  firing  began,  and  the  dis- 
tance of  the  target,  the  time  (by  the  order  of  firing)  when 
changes  of  fuze  or  elevation  are  ordered  and  the  observations  of 


Fig.  351. 


the  Captain. 

1659.  From  tliese  data  a plan  on  the  scale  of  one  inch  to 
sixteen  yards  should  be  made  giving  the  positions  of  the  several 
shot  on  the  plane  of  the  horizon.  All  shot  not  falling  within 
100  yards  of  the  target  should  be  rejected  and  reported  in  the 
aggregate  as  “ wild.” 


Accompanying  this  should  be  an  elevation  on  tlm  same 
scale,  of  the  ship’s  side,  transferred  to  which  are  all  the  shot 
which  would  have  struck  it.  This  is  easily  made  by  means  of 
tabulated  angles  of  fall  and  eq  (1)  of  the  preceding  article. 
(Art.  IGbO.) 

In  summing  up,  a proper  proportional  value  should  be  al- 
lowed for  any  difference  in  distance.  At  600  yds.,  the  IX-in., 
Xl-in.,  and  100-pdr.  are  equal.  At  1,300  yds.,  the  proportion 
of  hits  for  IX-in.  should  be  3,  for  T of  Xl-in.  or  100-pdr.  in 
the  same  number  of  rounds. 

With  the  same  guns,  the  hits  at  600  yds.  should  be  twice  as 
many  as  those  at  1200  yds.,  to  maintain  equality  of  firing. 

As  the  ordinary  variation  in  range  of  a gun  is  about  50  yds., 
the  sights  should  be  altered  only  when  the  distance  of  the  tar- 
get changes  by  more  than  that  amount. 

It  should  be  remembered  that  line  shots  over  will  appear  to 
fall  to  the  right  or  left  of  the  target  to  observers  on  the  right  or 
left  of  the  gun. 

1660.  QUOIXS  AXD  ELEVATIXG-SCREWS.— Most 


604 


NAVAL  ORDNANCE  AND  GUNNERY. 


]STaval  guns  are  now  fitted  with  elevating-screws,  passing  through 
a hole  in  the  caseabel  or  attached  to  the  carriages ; hut  the  ordi- 
nary beds  and  quoins  are  also  still  in  use ; they  are  arranged  to 
allow  the  extreme  elevation  and  depression  of  the  guns  which 
the  ports  will  admit  with  safety.  "When  the  inner  or  thick  end 
of  the  quoin  is  fair  with  the  end  of  the  bed  in  place,  the  gun 
is  level  in  the  carriage,  or  horizontal,  when  the  ship  is  upright. 

The  degrees  of  elevation  above  this  level,  which  may  be  giveu 
to  the  gun  by  di’awing  out  the  quoin  when  laid  on  its  base,  are 
marked  on  the  side  or  edge,  and  those  of  depression  on  the 
fiat  part  of  the  quoin,  so  that  when  the  quoin  is  turned  on  its 
side  for  depression  the  marks  may  be  seen.  The  level  mark 
on  the  quoin  is  to  correspond  with  the  end  of  the  bed.  When 
the  quoin  is  entirely  removed,  and  the  breech  of  the  gun  rests 
on  the  bed,  the  gun  has  its  greatest  safe  elevation ; and  when 
the  quoin  is  pushed  home  on  its  side,  the  gun  has  the  greatest 
safe  depression  that  the  port  will  admit. 

Care  must  be  taken  that  the  stop  on  the  quoin  is  always 
properly  lodged,  to  prevent  the  quoin  from  fiying  out  or  chang- 
ing its  position,  and  that  the  bed  is  secured  to  the  bed-bolt. 

Porter’s  bed  and  quoin  (Fig.  352)  has  been  adopted  for  all 
carriages  requiring  quoins.  This  quoin,  being  graduated  to 


whole  degrees,  requires  a small  additional  quoin  for  slight  dif- 
ference of  elevation  in  smooth  water. 

1661.  AVhen  the  elevating-screw  is  used,  a quoin  should  he 
at  hand  to  place  under  the  breech  of  the  gun,  when  at  extreme 
elevation,  to  relieve  the  screw  from  the  shock  of  the  discharge, 
and  prevent  a change  of  the  elevation,  as  well  as  to  take  the 
place  of  the  screw  if  it  should  be  disabled. 

1662.  When  the  fire  is  continuous  at  the  same  distance,  the 
lever  of  the  elevating-screw  should  be  secured  by  a lanyard,  to 
prevent  the  screw  from  tni'ning  and  altering  the  elevation. 

1663.  To  obtain  i-eadily  the  changes  of  elevation  necessaiy 
in  the  use  of  rifie-guns,  the  heavier  calibres  are  made  with  very 


POINTING. 


605 


small  preponderance,  and  arc  supplied  -svitli  an  elevating-screw 
whicli  is  attached  to  the  carriage  at  the  lower  end,  while  the 
nut  is  connected  with  the  cascabel  of  the  gun. 

Both  screw  and  nnt  admit  of  movements  by  which  the 
screw  can  take  any  position  required  in  the  various  degrees  of 
elevation.  The  parts  should  be  allowed  a certain  amount  of 
play. 

1664.  Dahlgren’s  screw  is  a single  screw  working  through 
the  cascabel  and  resting  in  a saucer  in  the  carriage. 

1665.  Hart’s  screw  consists  of  a male  and  female  screw  at- 
tached to  the  carriage. 

1666.  Pointing  Gtuns  and  Howitzers. — In  ordinary  firing 
it  is  not  supposed  that  the  trajectory  changes  its  position  with 
reference  to  the  lines  of  sight  and  fire  for  angles  of  elevation 
and  depression  less  than  15°.  In  aiming  at  any  object,  there- 
fore, the  angle  of  elevation  of  which  is  less  than  15°,  aim  as 
though  it  were  in  the  same  horizontal  plane  with  the  piece. 

1667.  In  pointing  guns  and  howitzers,  under  ordinary  angles 
of  elevation,  the  piece  is  first  directed  towards  the  object  and 
then  elevated  to  suit  the  distance.  The  accuracy  of  the  aim  de- 
pends, 1st : on  the  fact  that  the  object  is  situated  in  the  plane 
of  sight.  2d : that  the  projectile  moves  in  the  plane  of  fire, 
and  that  the  planes  of  sight  and  fire  coincide  or  are  parallel  and 
near  to  each  other.  3d  : on  the  accuracy  of  the  elevation. 

The  first  of  these  conditions  depends  on  the  eye  of  the  gun- 
ner and  the  accuracy  and  delicacy  of  the  sights ; the  errors  un- 
der this  head  are  of  but  little  practical  importance. 

1668.  When  the  trunnions  of  the  piece  are  horizontal  and 
the  sights  are  properly  placed  on  the  surface  of  the  piece,  the 
planes  of  sight  and  fire  will  coincide ; but  when  the  axis  of  the 
trunnions  is  inclined  and  the  line  of  sight  is  oblique  to  the  axis 
of  the  bore,  the  planes  are  neither  parallel  nor  coincident,  and 
the  aim  will  be  incorrect. 

1669.  When  the  line  of  sight  is  parallel  to  the  line  of  fire — 
as  when  the  tangent-sight  is  at  level — the  planes  of  sight  and 
fire  will  be  parallel  and  at  a distance  from  each  other  equal  to 
the  radius  of  the  breech  multiplied  by  the  sine  of  the  angle 
which  the  trunnions  make  with  the  horizon. 

To  show  this,  let  the  circle,  A B C D (Fig.  353),  represent  the 
■section  of  the  breech  of  the  piece  taken  at  right  angles  to  the 
axis,  and  C the  projection  of  the  natural  line  of  sight ; upon 
this  plane  let  A'  B''  be  the  inclined  position  of  the  trunnions.  C' 
marks  the  revolved  position  of  the’  line  of  sight,  and  C'  D', 
the  trace  of  the  plane  of  sight  Avhich  is  parallel  to  C D,  the 
plane  of  fire.  As  the  Ihies  of  sight  and  fire  are  parallel  in  their 


606  NAVAL  ORDNANCE  AND  GUNNERY. 

revolved  position,  tlie  planes  of  sight  and  fire  must  also  be 
parallel. 

The  angle  CO  C'  = B OB', 
therefore  C C'  = O C'  sin  B O B'. 

It  is  easily  seen  that  in  this  case 
the  error  of  pointing  can  never 
excejd  the  radius  of  the  breech. 
By  an  inspection  of  the  figure,  it 
will  also  be  seen  that  in  the  re- 
volved position  of  the  line  of  sight, 
the  elevation  is  diminished  by  a 
small  quantity,  which  is  equal  to 
the  versed  sine  of  the  arc  C C'. 

1670.  When  the  tangent-scale 
is  raised  and  the  line  of  sight  is 
no  longer  parallel  to  the  line  of  fire,  the  planes  of  sight  and 
fire  intersect  at  a short  distance  from  the  muzzle ; hence  it  fol- 
lows, that  as  the  object  is  situated  in  the  plane  of  sight,  the  pro- 
jectile will  deviate  from  the  object  to  the  side  on  which  the 
lower  trunnion  is  situated,  and  at  a distance  from  it  which  is 
proportional  to  the  distance  of  the  object  from  the  piece. 

This  is  shown  in  Fig.  3o4,  where  the  piece  is  directed  by 


the  notches  at  A and  C on  the  object,  B.  The  shot  will  pro- 
ceed in  the  line,  D E,  to  the  right  of  the  object,  B,  and  at  long 
range  this  deflection,  B E,  would  be  considerable. 

1671.  This  cause  of  deviation  is  very  common  on  ship-board, 
for  the  motion  of  the  vessel  renders  it  very  uncertain  that  the 
axis  of  the  trunnions  will  be  horizontal  at  the  moment  that  the 
gun  is  fii’ecl.  The  guns  forward  and  aft  are  particularly  sub- 
jected to  the  disadvantage  arising  from  this  cause,  on  account 
of  the  shear  of  the  ship,  and  the  guns  amidships  are  usually 
more  accurate  in  practice,  because  they  rest  ou  a more  level 
platform. 


POINTING. 


G07 


1673.  lu  chase-fir  in  deviation  must  he  tahen  into  con- 

sideration. . The  pursuing  and  pursued  have  generally  a consider- 
able heel  or  inclination  to  leeward ; in  consecpienee  of  this,  the 
trunnions  of  the  guns  in  the  bow  and  stern  parts  of  each  are  in- 
clined, and  in  pointing  them  it  will  be  necessary  to  aim  at  the 
weathermost  part  of  the  hull  in  order  to  avoid  the  effect  of 
this  error.  The  proper  elevation  due  to  the  distance  must  be 
given ; as  although  the  tangent-sight  is  slightly  lowered  by 
the  heel  of  the  ship,  vet  it  is  of  no  practical  importance. 

These  deviations  will,  of  course,  increase  with  the  elevation 
of  the  gun  and  its  distance  from  the  target.  To  give  an  idea 
of  their  extent,  suppose  the  plane  to  have  an  inclination  of  10°  ; 
distance  of  target,  900  yards ; elevation,  6° : the  lateral  de- 
viation will  be  six  yards,  and  the  projectile  will  strike  too  low 
by  about  20  inches;  if  the  inclination  is  but  5°,  the  lateral  de- 
viation is  reduced  to  3 yards,  and  the  fall  to  live  inches. 

Then  to  correct  for  this  source  of  error : point  a little 
above  the  target  and  towards  the  side  of  the  elevated  trunnion, 
and  make  the  corrections  proportionally  greater  as  the  distance 
of  the  target  and  elevation  of  the  gun  are  increased. 

1673.  PonsrxnsTG  Sm^vll-arms  and  Moetaks.— In  pointing 
small-arms  and  mortars  the  piece  is  first  given  the  elevation, 
and  then  the  direction  necessary  to  attain  the  object. 

1674.  Pointing  Small-aevis. — The  rear-sights  of  small-arms 
are  graduated  with  elevation-marks  for  certain  distances,  gener- 
ally every  hundred  yards;  in  aiming  with  these,  as  with  all 
other  arms,  it  is  first  necessary  to  know  the  distance  of  the  ob- 
ject. This  being  known,  and  the  slider  being  placed  opposite 
the  mark  corresponding  to  this  distance,  the  bottom  of  the  rear- 
sight-notch  and  the  top  of  the  front-sight  are  brought  into 
a line  joining  the  object  and  the  eye  of  the  marksman. 

The  term  coarse-sight  is  used  when  a considerable  portion 
of  the  front-sight  is  seen  above  the  bottom  of  the  rear-sight- 
notch  ; and  the  tenn  fine-sight  when  but  a small  portion  is  seen. 

The  graduation  marks  being  determined  for  a fine-sight, 

the  effect  of  a coarse-si2:ht  is  to  increase  the  true  range  of  the 

• -1  ° ° 
projectile. 

1675.  Pointing  Moetaes. — First  give  the  elevation  by  ad- 
justing the  quoin  or  ratchet  until  the  required  number  of  de- 
grees is  obtained  ; then  the  direction  is  given.  The  circle  on 
wh.ieh  the  mortar  stands,  being  fitted  with  eccentrics  is  made  to 
revolve  so  as  to  point  the  mortar  at  the  object  without  the 
trouble  of  swinging  the  vessel  or  moving  the  mortar  around 
with  handspikes.  The  elevation  is  given  with  gunner'' s quad- 
rant^ the  sj)irit-level-quadrant,  or  the  trunnion-sight. 


608 


NAVAL  OEDNANCE  AND  GUNNERY. 


1676.  Gunner’s  Quadrant. — This  is  made  of  brass  and 
consists  of  a quarter  of  a circle  fixed  to  a long  arm.  (Fig.  355.) 


Fig.  355. 


The  edge  of  the  circle  is  divided  into  degrees,  and  the  inclina- 
tion of  the  arm  to  the  horizon  is  determined  hv  a plummet 
which  is  fastened  at  the  centre  of  the  curve.  This  quadrant 
gives  the  elevation  only  to  within  a degree.  To  use  it  place 
the  arm  in  the  muzzle  with  the  quadrant  down ; raise  tlie  muz- 
zle until  the  plumb-line  cuts  the  required  augle  on  the  gradu- 
ated arc. 

1677.  Spirit-level  Quadrant. — This  is  similar  to  the  gun- 
ner’s quadrant,  having  instead  of  the  plumb-line  a movable 
limb  fastened  at  the  centre  of  the  arc,  and  a spirit-level  attached 
to  it.  The  end  of  this  limb  moves  along  the  graduated  arc,  and 
has  on  it  a vernier,  by  means  of  which  parts  of  a degree  can  be 
read  off.  (Fig.  356.) 


This  instrument  is  more  especially  intended  for  use  with 


POINTING. 


609 


long  pieces  of  large  calibre,  when  firing  at  great  elevations. 
To  use  it,  insert  the  long  arm  into  the  bore,  with  the  quadrant 
up  ; there  is  a stop  on  the  under  side  of  the  arm  to  prevent  its 
slipping  into  the  chamber ; the  spirit-level  attached  to  the 
graduated  arc  being  set  to  the  required  angle,  and  the  piece 
elevated  until  the  spirit-level  becomes  horizontal,  which  will 
appear  by  the  bubble  resting  in  the  centre  of  the  glass  tube. 
(Art.  964.) 

1678.  Trunnion-Sight. — This  consists  of  a bar  of  mahogany 
or  other  hard  wood  not  liable  to  warp  (Fig.  346),  of  about  forty 
inches  in  length,  two  inches  wide,  and  one  inch  thick,  with  a 
brass  notch  at  the  rear  end  and  a point  at  the  other,  so  placed 
that  an  imaginary  line  from  the  top  of  the  point  to  the  bottom 
of  the  notch  is  parallel  to  the  upper  edge.  A semicircular 
plate,  graduated  to  degrees,  is  attached  to  the  middle  of  the 
har,  so  that  the  bar’s  upper  edge  corresponds  to  the  0 of  the 
graduation.  A small  spirit-level  is  let  into  the  upper  surface 
of  the  rear  end  of  the  bar,  and  a stout  thumb-screw  passes 
through  the  bar  and  the  centre  of  the  semi-circulai*’ plate. 

To  use  this  instrument  a screw-hole  is  tapped  in  the  axis  of 
the  left  trunnion  to  receive  the  thumb-screw  ; a line  is  marked 
on  the  trunnion  perpendicular  to  the  axis  of  the  piece  and 
passing  through  the  axis  of  the  trunnions.  The  sight  is  se- 
cured by  the  thumb-screw,  with  its  rear  end  raised  until  the 
mark  on  the  trunnion  coincides  with  the  degree  of  elevation  re- 
quired. The  piece  is  now  elevated  until  the  sight  is  level, 
which  will  be  indicated  by  the  spirit-level.  This  instrument  is 
also  designed  to  be  used  with  pivot-guns  when  the  required  ele- 
vation passes  the  limits  of  the  other  sights. 

1679.  To  give  Lateral  Train  in  mortar  firing  the  trunnion- 
sight  ma)"  be  used,  or  it  can  be  done  by  a white  line  diuwn  on 
the  exterior  of  the  mortar,  in  the  same  vertical  plane  as  the  axis 
of  the  piece  when  the  trunnions  are  horizontal.  The  line  is 
sometimes  painted  on  the  mortar-bed. 

In  pointing  mortars  on  shore  it  is  an  easy  matter  to  get  the 
direction,  because  the  mortar  is  stationary  ; but  on  ship-board, 
owing  to  the  motion,  it  is  attended  with  difficulty,  especially  when 
the  vessel  is  rolling,  and  the  line  of  fire  can  only  be  approximate. 

1680.  On  shore,  the  plan  of  giving  the  direction  is  to  de- 
termine practically,  two  fixed  points,  which  shall  be  in  a line 

"with  the  piece,  and  the  object,  and  sufficiently  near  to  be  readily 
distinguished  by  the  eye.  A plummet  is  held  in  the  hand  im- 
mediately behind  the  mortar  and  the  string  made  to  coincide 
with  these  points.  The  mortar  is  then  trained  until  the  line  of 
the  plummet  covers  the  central  line  on  the  mortar. 

39 


610 


NAVAL  ORDNANCE  AND  GUNNERY. 


1681.  In  mortars,  if  the  axis  of  the  trunnions  is  not  hori- 
zontal, the  vertical  plane  passing  through  the  line  of  sight  vill 
still  be  parallel  to  the  vertical  plane  of  fire,  and  may  be  taken 
for  it,  so  that  it  is  not  necessary  to  have  the  platform  of  mor- 
tars horizontal. 

1682.  Beaeing  or  the  Eneihy. — It  frequently  happens  in 
action  that  ships  become  quickly  enveloped  in  a cloud  of  smoke 
so  dense  that  when  looking  through  the  ports  everything  be- 
yond the  muzzles  of  the  guns  will  he  invisible.  But,  though 
objects  are  thus  shut  out  from  the  view  of  the  battery,  a mast 
or  a spar  may  generally  be  seen  from  the  upper  deck  sufficient- 
ly defined  to  mark  the  position  of  a vessel,  and  enable  her  bear- 
ings to  be  accurately  taken  either  b}^  compass  or  by  pointers. 

The  principal  care  of  the  Commander  must  be  to  keep  his 
guns  always  bearing  on  the  enemy,  and  never  pass  the  limits  of 
extreme  train  for  all  his  guns,  unless  absolutely  necessary  in 
mancBuvriug. 

1683.  Dieectoe. — This  may  be  regulated  by  the  aid  of  a 
hearing-plate,  or  director,  fittecl  in  a convenient  position  on  the 
upper  deck.  It  is  a species  of  alidade  working  on  a graduated 
circle  and  giving  the  angular  bearing  of  the  object.  The  arc  is 
marked  in  degrees  and  points,  and  the  several  bearings  of  con- 
centration are  indicated  as  well  as  the  dinlits  of  extreme  train 
for  all  the  guns. 

The  sights  of  the  alidade  are  graduated  so  as  to  be  set  to 
any  degree  of  elevation  or  depression,  according  to  the  heel  of 
the  ship. 

1681.  In  Pointing,  the  amount  of  lateral  train  required  is 
usually  designated  by  points,  and  the  elevation  by  the  corre- 
sponding number  of  yards  of  range. 

In  tlie  case  of  guns  which  work  upon  pivots  or  on  centres, 
the  motion  of  the  rear  of  the  gun-carriage  being  strictly  con- 
fined to  the  arc  of  a circle,  the  position  of  the  gun  with  refer- 
ence to  the  vessel  can  always  be  exactly  defined  by  an  arc  di- 
vided into  points,  half-^ioints,  and  quarterqioints,  being  marked- 
on  the  deck. 

The  ordinary  broadside  carriage,  having  no  centres  or  pivots 
to  work  on,  will  rarely  occupy  the  same  place  in  the  ports  when 
the  ffuns  are  run  out  for  firiim,  so  that  an  arc  marked  on  the 
deck  would  not  be  strictly  applicable. 

1685.  CoNCENTEATED  PiEE. — IVlieii  all  the  guns  of  a bat- 
tery are  directed  to  the  same  point  and  are  discharged  simul- 
taneously, it  is  called  “ concentrated  firing.”  This  kind  of  firing 
is  used  to  the  greatest  advantage  at  short  distances.  One  of 
the  guns  of  the  battery  is  selected  as  the  directing-gun. 


POINTING. 


611 


To  Concentrate  a Ship’s  Broadside^  the  guns  are  trained  in 
the  direction  of  the  object  by  means  of  The  Directing-ljatten^  or 
The  Converging-line^  and  laid  according  to  the  heel  of  the  ship 
and  the  distance  of  the  object : the  direction  being  given  by  the 
aid  of  the  Director  from  the  upper  deck. 

. 1686.  The  Dieecting-battens. — These  consist  of  metal  or 
wooden  battens,  a (Fig.  357),  sliding  in  two  beckets  attached  to 


each  of  the  brackets  of  the  carriage,  and  retained  in  any  position 
by  a thumb-screw.  They  are  arranged  to  slide  out  parallel  to 
the  deck,  directly  to  the  rear  of  the  carriage. 

The  upper  sides  of  the  battens  are  marked  for  the  converg- 
ence on  the  bow,  beam  or  quarter,  and  the  outer  sides  in  de- 
grees for  parallel  firing. 

To  give  direction,  one  of  the  battens  is  clamped  at  zero,  the 
zero  mark  coinciding  with  the  rear  face  of  the  becket  in  which 
it  slides;  the  other  batten  is  drawn  out  to  the  mark  designating 
the  points  of  convergence  ordered,  and  clamped.  A cord  or 
bar  is  now  placed  over  the  ends  of  the  two  battens  and  the  gun 


612 


NAVAL  ORDNANCE  AND  GUNNERY. 


trained  until  this  is  parallel  to  a mark  on  the  deck  indicating 
the  direction  of  the  keel. 

1687.  The  Converging-line.  — This  is  a line  hooked  to 
tlie  centre  and  near  the  outside  of  the  upper  port-sill,  and  held 
immediately  under  marks  made  on  the  beams  or  deck  over- 
head, for  the  several  bearings  of  a-beam,  on  the  bow  and  ipiarter ; 
when  the  gun  is  trained  until  the  sights  are  parallel  to  it. 

The  midship  gun  is  usually  employed  as  the  directing-gun, 
and  the  angles  of  training  ascertained  for  the  different  bearings 
at  a constant  distance  of  say  500  yards.  Tliough  the  calcnla- 
tions  are  made  for  this  distance,  yet  this  method  of  training 
will  answer  for  all  ranges  within  1,000  yards. 


1688.  To  Calculate  the  Angles  for  Concentration. — ■ 
On  the  Beam. — Let  A (Fig.  358)  be  the  midship  gun  trained 

right  a-beam,  B the  foremost  one,  C 
the  object  at  a constant  distance  of  500 
yards.  Let  the  distance  from  A to  B, 
supposed  known,  ecpial  96  feet,  and 
the  distance  from  the  centre  of  port 
in-hoard  be  taken  as  11  feet,  being  the 
same  for  all  the  guns.  Then  the  an- 
gle C can  be  easily  found  for  ~ = Tan. 
C,  the  angle  of  training  for  the  fore- 


most gnn. 


the 

the 

the 


tangent 


Again,  in  triangle  B D E,  we  have 
D E = B D • Tan.  C,  the  length  of 
off  overhead,  from  the  point  opposite 
For  the  intermediate  guns  divide 


to  be  set 

centre  of  the  port, 

D E by  the  number  of  guns  before  the  midship 
one,  which  will  give  the  length  of  the  tangent  before  the  gun 
next  to  the  midship  one  ; twice  tins  will  be  the  length  for  the 
next  gun,  and  so  on  : Thus,  if  D E = 10.7  inches,  and  the  num- 
ber of  giuis  before  A be  8,  we  have  =1.3  inch,  or  the  length 

for  the  gun  next  to  A ; 2.6  in- 
ches = the  length  for  the  next 
gun,  and  so  on.  The  same 
measurement  answering  for  the 
guns  abaft  A. 

1689.  On  the  Bow  or  Quar- 
ter.— Let  A (Fig.  359)  be  the 
midship  gun  trained  3 points 
abaft  the  beam,  B the  foremost 
one,  C the  object  distant  500 
yards.  Let  the  distance  from  A 


0 e 


Fig.  359. 


F C 


POINTING. 


613 


to  B,  supposed  known,  equal  96  feet,  and  the  distance  from  the 
centre  of  the  port  in-board  equal  Id  feet  as  before.  Then  from 
the  expression, 

A C -f  A B _ Tan.  d (B  -f  C) 

A C - A B “ Tan.  (B  — C) 
the  angle  B can  be  easily  found,  which,  taken  from  90°,  will 
give  the  angle  of  training  for  the  foremost  gun.  Again,  in  tri- 
angles A i)  E,  B F G,  we  have  D E = A D • Tan.  A and 
F G = F B • Tan.  B,  which  are  the  required  lengths  of  the 
tangents  to  be  set  ofi  overhead  from  the  points  opposite  the 
centres  of  these  ports.  For  the  intermediate  guns,  divide  the 
difference  between  the  two  lengths  D E and  F G by  the  num- 
ber of  guns  before  the  midship  one,  and  add  this  common  diffe- 
rence to  the  length  D E for  the  gun  next  before  the  midship  one, 
and  so  on  to  each  gun  in  succession.  Thus,  let  F G = 10  ft.  5 
in.,  and  D E = 9 ft.  4 in.,  tlie  difference  = 1 ft.  1 in.;  let  the 
number  of  guns  before  A be  8,  then  we  have  = 1.6  in.,  the 

common  difference  for  each  gun ; therefore  9 ft.  5.6  in.  = the 
length  for  the  gun  before  A ; 9 ft.  7.2  in.  = the  length  for  the 
next  gun,  and  so  on. 

The  measnrements  for  the  corresponding  guns  abaft  the  mid- 
ship one  will  be  found  by  subtracting  the  common  difference 
from  D E,  and  so  on,  from  each  gun  in  succession. 

The  calculation  of  the  angles  for  3 points  before  the  beam, 
or  for  1-|-  points  before  and  abaft  the  beam,  is  performed  in  the 
same  manner. 

1690.  To  jMaek  the  Beams. — Having  a line  parallel  to  the 
keel,  overhead,  at  any  convenient  distance  in  rear  of  the  guns, 
measure  the  assumed  distance  IF  ft.  from  the  centre  of  port  in- 
board, and  place  a perfectly  straight-edged  batten  there,  parallel 
to  the  keel  line ; then  transfer  the  centre  of  the  port  to  the  bat- 
ten by  stretching  a line  taut  across  from  the  centre  of  two  op- 
posite upper  port-sills ; or  with  any  length  of  line  as  radius, 
from  the  centre  of  the  port,  describe  an  arc  cutting  the  batten 
before  and  abaft  the  centre ; half  the  distance  between  these 
marks  will  give  the  point  corresponding  to  the  centre  of  the 
port.  From  this  centre,  measure  off  on  the  batten,  to  the  right 
and  left,  the  lengths  of  the  tano;ents  for  the  different  bearings,  as 
calculated  above ; and  then  transfer  these  points  to  the  beams 
or  deck  immediately  over  the  batten. 

1691.  The  Elevation. — Each  turn  of  the  elevating-screw 
represents  1°  ; therefore,  if  the  gun  is  once  levelled,  by  stretch- 
ing a line  across  from  tbe  reinforce  sights  of  opposite  guns,  and 
raising  the  screws  until  this  line  just  touches  the  bottom  of  the 


614 


KAVAL  ORDNANCE  AND  GUNNERY. 


sight-notch  at  level,  and  the  number  of  threads  above  the  cas- 
cabel  noted,  it  is  apparent  that  each  turn  raises  or  lowers  the 
breech  by  1°,  and  that  the  gun  can  be  first  made  parallel  witli 
the  deck  and  then  laid  level  to  compensate  for  the  degree  of 
lieel  given  by  the  pendulum  or  director. 

1692.  Pendulums  to  Marh  the  Heel  of  the  Ship. — The 
tangent  sights  give  the  elevation  of  the  gun  above  the  horizon- 
tal plane,  and  when  the  deck  is  steadily  inclined  from  the  hori- 
zontal line,  by  the  pressure  of  the  wind  for  instance,  the  tan- 
gent-scale will  give  the  elevation  of  the  gun  above  the  plane  of 
the  deck,  and  not  above  the  plane  of  the  sea. 

Pendulums  are  fitted  in  convenient  localities,  working  in  a 
graduated  arc,  to  indicate  the  amount  of  heel  or  inclination  at 
any  time,  and  show  the  nninber  of  degrees  of  elevation  or  de- 
pression required  to  bring  a ship’s  guns  to  a horizontal  position. 
In  practice,  howevei’,  very  little  reliance  is  placed  upon  these 
contrivances  (Art.  1660). 


Section  II.— Different  Kinds  of  Fire. 


1693.  Classification. — The  different  kinds  of  fires  are  dis- 
tinguished, 1st.  By  the  flight  of  the  projectile,  as  direct.,  curved, 
ricochet,  and  plunging-fires  y 2d.  By  the  nature  of  the  projec- 
tile, as  solid-stiot,  shell,  shrapnel,  grape,  and  canister  fires  ; and 
3d.  By  the  angle  of  elevation,  as  horizontal  fire,  or  the  fire  of 
guns  and  howitzers  under  low  angles  of  elevation,  and  verti- 
cal fire,  or  the  fire  of  mortars  under  high  angles  of  elevation. 

1691.  Dieect  Fire. — A fire  is  said  to  be  direct  wlien  the  pro- 
jectile hits  its  object  before  striking  any  intermediate  object, 
as  the  surface  of  the  ground  or  water. 

This  species  of  fire  is  employed  where  great  penetration  is 
required,  as  the  force  of  the  projectile  is  not  diminished  by  pre- 
vious impact ; it  is  necessarily  employed  for  shrapnel  fire  and 
for  rifle-projectiles,  which  from  their  form  are  liable  to  be 
deflected  by  previously  striking  a resisting  substance. 

This  kind  of  fire  requires  a good  knowledge  of  distance,  and 
precision  both  of  elevation  and  lateral  direction,  in  order  to 
strike  an  object  which  is  comparatively  a point.  It  is  always  to 
be  preferred  when  the  distance  is  accurately  known,  or  when 
the  object  is  so  near  that  the  chances  of  hitting  it  are  very 
great ; also  when  the  intervening  surface  between  the  gun  and 
object  is  so  rough  or  irregular  that  a projectile  striking  it  would 


DIFFERENT  KINDS  OF  FIRE. 


615 


have  its  velocity  much  diminished  or  destroyed,  and  its  direction 
injuriously  affected. 

1695.  Ricochet  Fere. — When  the  angle  of  fall  is  small 
enough,  the  projectile  rises  and  continues  to  move  on,  forming  a' 
series  of  bounds  or  ricochets.  A ricocheting  ball  makes  a 
furrow  in  the  surface  struck,  and  each  time  the  angle  under 
which  it  leaves  that  surface  is  greater  than  that  under  Avhich  it 
enters  it ; for,  having  lost  a portion  of  its  velocity  in  passing 
over  the  first  part  of  the  curve,  it  has  no  longer  the  same  power 
to  overcome  resistance,  and  must  pass  out  hy  a shorter  path  than 
the  one  it  followed  in  entering,  and  consequently  the  angle  is 
increased,  which  causes  the  more  or  less  rapid  extinction  of  the 
ricochet. 

The  number,  shape,  and  extent  of  the  ricochets  depend  on 
the  nature  of  the  surface  struck,  the  initial  velocity,  shape,  size, 
and  density  of  the  projectile,  and  on  the  angle  of  fall. 

1696.  The  most  favorable  circumstances  under  which  this 
fire  occurs  are  where  the  angle  of  fall  is  least,  and  the  surface 
perfectly  smooth.  A 32-lb.  spherical  projectile  will  then  roll 
3000  to  3500  yards  on  water,  rising  hut  little  above  the  surface 
— never  as  high  as  the  hull  of  a frigate — while  the  greatest 
range  obtained  from  an  elevation  of  5°  with  the  same  gun  and 
charge  is  less  than  1800  yards. 

At  first  the  bounds  are  of  considerable  extent,  perhaps  350 
to  400  yards  between  the  first  and  second  grazes ; they  diminish 
gradually,  so  as  to  leave  intervals  not  exceeding  fifty  yards  as 
they  approach  the  end  of  the  range,  and  finallj'  roll  along  the 
top  of  the  water  as  if  ploughing  it.  Long  before  this,  how- 
ever, they  are  apt  to  curve  off  to  the  right  or  left  from  the  true 
direction,  so  as  to  make  an  extreme  deviation,  often  amounting 
to  100  or  200  yards. 

1697.  Ricochet  firing,  properly  so  called,  is  performed  at 
level,  or  at  most  at  three  degrees  of  elevation ; shot  Avill  often 
ricochet  at  much  greater  angles,  but  it  is  not  what  is  meant  by 
ricochet  firing. 

Upon  smooth  surfaces  within  certain  distances  this  fire  has 
some  important  advantages  over  direct  firing.  When  the  guns 
have  very  little  or  no  elevation  and  are  near  the  water,  as  they  are 
in  a ship's  battery,  theprojectile  strikes  the  water  at  a very  small 
angle ; its  flight  is  not  greatly  retarded  by  the  graze,  and  it 
rises  but  little  above  the  surface  in  its  course,  but  the  penetra- 
tion is  not  to  be  depended  upon  beyond  1500  yards  against  ships 
of  Avar. 

1698.  Ricochet  firing  at  Ioav  elevations  requires  only  correct’ 
lateral  direction,  since  the  projectile  would  rarely  pass  over,  and 


616 


NAVAL  ORDNANCE  AND  GUNNERY. 


would  probably  strike  a vessel,  if  within  its  effective  rang-', 
whether  the  actual  distance  had  been  ascertained  or  not. 

The  deviation  of  projectiles  is,  however,  generally  increased 
by  ricochet,  and  in  proportion  to  the  roughness  of  the  surface 
of  the  water.  Even  a slight  ripple  will  make  a perceptible  dif- 
ference, not  only  in  direction,  but  in  range  and  penetration,  and 
the  height  to  which  the  projectile  will  rise  in  its  bounds. 

1699.  Although  these  facts  demand  attention,  yet  when  the 
estimated  distance  does  not  require  an  elevation  of  more  than 
three  degrees,  projectiles  from  guns  pointed  rather  too  low  for 
direct  tiring  will  probably  ricochet  and  strike  the  object  with 
effect,  even  when  the  water  is  considerably  rough.  This  may 
be  called  “ accidental  ricochet.” 

When  the  water  is  not  smooth,  the  most  favorable  circum- 
stances for  ricochet-tiring  are  when  the  tlight  of  the  projectile 
is  with  the  I'oll  of  the  sea,  and  the  roll  is  long  and  regular. 

1700.  Ricochet  will  be  effective  against  small  objects  up  to 
2000  yards,  but  should  not  commence  at  less  than  600  yards ; 
at  less  distances  it  is  preferable  to  tire  direct. 

Ricochet  is  of  no  value  from  rifled  guns  firing  elongated 
projectiles,  as  they  lose  all  certainty  of  direction  on  the  rebound. 

Projectiles  rarely  ricochet  at  all  with  elevations  above  5°,  and 
the  bounds  are  always  higher,  with  equal  charges  from  the  same 
gun,  as  the  elevation  of  the  gun  is  increased. 

1701.  Curved  Eire. — When  a projectile  is  fired  so  as  just 
to  clear  an  interposing  cover  and  then  descend  upon  tlie  object 
without  ricochets  or  rebounds,  such  j^i’^ctice  is  termed  curved 
fire. 

Smallei-  charges  and  higher  angles  are  required  than  for 
ordinary  direct  fire.  On  shipboard  it  is  more  convenient  to  tire 
with  service-charges  from  such  distances  as  to  obtain  the  proper 
angle  of  fall. 

1702.  Plunging  Fire. — A fire  is  said  to  be  plunging  when 
the  object  is  situated  below  the  piece.  This  tire  is  particularly 
effective  against  the  decks  of  A-essels. 

1703.  Solid-Shot  Firing. — Solid  shot  are  generally  used 
when  great  accuracy  at  very  long  range  and  penetration  are 
required.  From  their  great  strength  they  can  be  tired  with  a 
large  charge  of  powder,  Avhich  gives  them  great  initial  velocity  : 
and  having  great  density,  which  diminishes  the  effect  of  the 
resistance  of  the  air,  they  have  great  range  and  accuracy. 

In  rifle-guns  of  large  calibre  it  is  found  that  solid  shot  s^'rain 
the  guns  from  their  weight,  and  shoot  comparatively  badly  from 
their  length,  which  is  usually  less  than  that  of  shell.  It  appears 
that  the  minimum  length  for  good  shooting  is  two  calibres,  and 


DIFFERENT  KINDS  OF  FIRE. 


617 


that  shell  have  an  advantage  from  having  the  weight  so  diS' 
posed  as  to  give  a longer  radius  of  gyration,  and  therefore  a 
better  spin. 

ITOd.  Shell-Firing. — The  diameter  and  velocity  of  two  pro- 
jectiles being  the  same,  the  retarding  effect  of  the  air  is  inversely 
proportioned  to  their  weight ; hence  a shell  has  less  accuracy 
and  range  than  a solid  shot  of  the  same  size.  The  shot  has 
superior  accuracy,  lait  the  shell  superior  power,  as  it  acts  both 
by  impact  and  explosion. 

If  there  be  any  difliculty  in  striking  a given  object,  the  shot 
will  do  so  oftener  than  the  shell  ; or  the  shot  will  cluster  more 
closely  about  any  desired  spot.  On  the  other  hand,  the  power 
exerted  by  a single  exploding  shell  is  infinitely  more  destruc- 
tive than  that  of  many  shot.  The  shot  has  greater  penetration, 
but  the  shell  does  not  require  this  property  to  the  same  extent, 
because  the  former  must  always  perforate  entirely  to  operate 
with  effect,  while  the  action  of  the  latter  will  be  materially 
lessened  in  its  explosive  power,  if  it  does  pass  through  instead 
of  lodging.  Hence,  it  may  be  assumed  that  the  penetration  of 
the  shell  is  adequate  to  its  special  purpose  at  any  distance  ivhere 
shot  of  like  weight  are  effective ; that  is,  if  the  shot  pass 
entirely  through,  the  shell  may  do  likewise  and  explode  in- 
board ; or  it  may  lodge  and  work  great  destruction  to  the  side. 

1705.  A shell  may  be  made  to  burst  either  while  in  motion 
or  when  at  rest ; in  the  first  case,  each  of  the  fragments  will 
have  a forward  velocity  proportioned  to  that  of  the  shell  at  the 
moment  of  fracture,  and  spreading  out  will  act  in  the  same  way 
as  a charge  of  grape;  while,  if  the  shell  is  stationary  when  it 
bursts,  its  effect  Avill  mainly  depend  upon  the  size  of  the  burst- 
ing charge  and  the  consequent  violence  of  explosion. 

Shells  may,  therefore,  be  considered  as  having  tivo  distinct 
applications ; they  may  be  used  as  missiles  or  as  mines.  As 
missiles  they  are  most  formidable,  and  most  generally  used 
against  personnel  of  an  enemy;  but  as  mines  they  are  most 
destructive  against  his  materiel. 

The  effects  of  shells  depend  in  part  upon  the  number  of 
fragments  produced  by  the  explosion. 

Shells  should  be  used  against  ships  at  all  distances  where 
the  penetration  Avoidd  be  sufficient  to  lodge  them.  They  are  of 
no  service  in  breaching  solid  stone  Avails,  but  are  A’ery  effective 
against  eartliAvorks,  ordinary  buildings,  and  for  bombarding. 

1706.  In  firing  shells  with  time-fuzes  it  is  necessary  to  knoAv 
the  time  of  flight,  in  order  to  regulate  the  burning  of  the  fuze 
for  the  range  required.  The  times  of  flight  can  be  found  with 
sufficient  accuracy  for  such  purposes  by  obsen-ation  ; but  they 


618 


NAVAL  ORDNANCE  AND  GUNNERY. 


may  be  rotigbly  calculated  for  low  angles  of  elevation  by  the 
formula — • 

t — \ y"  R (in  feet)  tan  a. 

Where  R = range, 

a — angle  of  elevation. 

Example. — An  8-inch  shell  is  fired  at  an  object  1400  yards 
distant,  and  for  this  raDge  fom-  degrees  of  elevation  is  required  ; 
find  the  time  of  flight. 


t = \ y 4200  X = 4.3  second. 

The  times  of  flight  found  by  the  above  formula  are,  however, 
too  short,  the  resistance  of  the  air  retarding  the  projectiles  in 
their  descent. 

1707.  At  ranges  from  1000  to  1100  yards,  the  3^-second 
fuze  is  employed. 

The  5-second  fuze  is  serviceable  between . .1200  and  1400  yards. 

The  7-second  fuze  between 1500  and  1700  “ 

The  10-second  fuze  between 1800  and  2000  “ 

At  ranges  exceeding  this,  fuzes  of  longer  time  are  em- 
ployed. 

It  is  best  to  employ  the  shortest  time  fuze  that  will  reach  the 
object,  because  its  combustion  is  more  powerful,  and  therefore 
less  liable  to  extinction  than  the  fuze  of  greater  duration. 

Tlie  times  of  flight  and  length  of  fuze  for  all  projectiles,  so 
far  as  ascertained,  are  given  in  the  Table  of  Ranges,  Ordnance 
Instructions. 

It  is  preferable,  when  circumstances  will  admit,  to  take  up 
sucli  distances  as  Avill  correspond  Avith  the  time  c>f  flight  of  one 
of  the  regulation  lengths.  When  tiring  against  ships  or  earth- 
Avorks,  the  fuze  should  be  a little  longer  than  necessary  in  order 
to  reach  the  object  before  bursting;  but  a little  shorter  wlien  fir- 
ing against  boats  or  masses  of  troops,  in  order  to  insure  its  burst- 
ing in  front  of  them. 

1708.  Shrapnel  Firing. — The  shrapnel  may  be  defined  as  a 
combination  of  the  shell  and  the  canister,  by  Avhich  the  former 
is  made  to  serve  as  a case  or  envelope  to  the  balls  of  the  latter, 
carrying  them  to  the  desired  point  near  the  object,  and  then 
opening  to  permit  their  egress.  Its  sphere  of  operation  can 
only  begin  Avhere  the  dispersion  of  the  common  canister  becomes 
too  great,  and  its  effect  feeble. 

With  shrapnel  the  effect  produced  by  the  bullets  will  chiefly 
depend  upon  the  bursting  of  the  sliell  at  exactly  the  required  in- 
stant ; no  precise  rule  can  be  absolutely  laid  doAvn  as  to  the  dis- 


DIFFERENT  KINDS  OF  FIRE. 


G19 


tiiDce  short  of  the  object  at  Avhich  the  shell  ought  to  hurst,  as  so 
much  will  depend  upon  the  yelocity  of  the  shell  just  before  it 
opens,  and  otlier  circumstances.  They  are  fired  with  the  hea- 
viest charges  allowed  for  the  guns. 

The  bursting  of  a shrapnel  at  the  proper  distance  is  of  the 
very  greatest  importance ; if  the  shell  hursts  too  soon,  the  whole 
or  greater  part  of  the  halls  will  fall  short,  the  velocity  and  pene- 
tratmg  power  being  greatly  diminished  in  consequence ; if  the 
shell  pass  the  object  before  exjiloding,  its  effect  as  a shrapnel 
will  be  entirely  lost. 

1709.  The  effect  of  shrapnel  greatly  depends  on  the  correct 
estimate  of  the  results  that  are  being  produced,  and  in  most  cases 
on  the  judgment  displayed  in  the  constant  efforts  to  improve  on 
the  shooting ; when  used  intelligently  the  effect  is  most  excel- 
lent. It  is  possible  generally  from  the  gun  to  estimate  the  line 
and  the  height  of  the  burst  of  the  shell,  but  not  the  distance  at 
which  it  occurs,  and  bad  practice  commonly  arises  from  a too 
sanguine  estimate  of  effects,  judging  from  the  appearance  of  the 
smoke  of  the  burst  alone ; particular  attention  slioidd  therefore 
be  paid  to  any  visible  marks  of  the  bullets  grazing;  on  water, 
splashes  will  be  seen  ; on  dry  ground,  puffs  of  dust ; and  the 
greater  their  velocity  at  the  moment  of  bursting,  the  greater 
will  be  the  effect. 

Shrapnel  should  be  used  from  300  to  900  yards  with  the 
12-pdrs.,  and  from  400  to  1500  yards  with  XTinch. 

A Avell-delivered  shrapnel  shell  from  a heavy  gun  must 
sweep  away  the  crew  of  a pivot  or  other  gun,  on  a spar-deck 
not  protected  by  bulwarks. 

1710.  HiJte-iSla'ajpnel. — The  effect  of  the  oblong  shrapnel 
is  said  to  he  inferior  to  that  of  the  spherical,  but  this  has  been 
disproved  by  practice.  At  all  ranges  the  effects  of  the  oblong 
shrapnel  are  found  to  be  superior  to  those  of  the  spherical. 

Such  a projectile  fired  from  a rifled  cannon,  having  previous 
to  breaking  up  a rotatory  motion,  considerable  lateral  spread  is 
given  to  the  bullets  when  released.  The  charge  is  usually 
placed  in  a chamber  at  the  base,  so  that  on  explosion  there  is  no 
tendency  to  increase  the  lateral  spread  of  the  bullets,  but  rather 
to  increase  their  velocity  and  penetration. 

1711.  Grape  AND  Canister  Firixg. — In  gi'ape  and  canister 
firing,  the,  apex  of  the  cone  of  dispersion  is  situated  in  the  muz- 
zle of  the  piece,  and  the  destructive  effect  is  confined  to  short 
distances.  The  shape  of  this  cone  is  the  same  as  in  shrapnel ; 
its  intersection  by  a vertical  plane  is  circular,  while  that  of  a 
horizontal  plane,  as  the  ground,  is  oval,  with  its  greatest  dia- 
meter in  the  plane  of  fire. 


620 


NAVAL  ORDNANCE  AND  GUNNERY. 


The  greatest  number  of  projectiles  are  found  around  tlie  axis 
of  the  cone,  while  the  extreme  deviations  amount  to  nearly  one- 
tenth  of  the  range.  ' 

Grape  and  canister  are  effective  at  short  distances  against 
boats,  exposed  bodies  of  men,  and  the  aigging  of  vessels.  Grape 
being  larger  than  canister,  are  effective  at  greater  distances. 
Canister  can  only  be  used  with  effect  at  short  ranges,  on  account 
of  the  rapid  dispersion  of  the  balls,  and  from  the  fact  that  their 
velocity  is  soon  lost  in  consequence  of  their  comparative  light- 
ness. 

1712.  The  fire  of  canister  does  not  always  ^produce  the  effect 
anticipated  for  it,  because  the  object  is  often  thought  to  be  near- 
er than  it  really  is,  and  the  firing  sometimes  commences  too 
soon  ; also,  the  danger  is  often  thought  to  be  more  imminent 
than  it  really  is,  and  consequently  proper  care  is  not  observed  in 
aiming. 

On  hard  fiat  ground,  the  effect  of  canister  depends  chiefly  on 
its  ricochet.  The  guns  being  level,  the  projectiles  will  effectual- 
ly sweep  the  ground  for  several  hundred  yards  in  front. 

When  the  men  on  the  spar-decks  of  the  enemy  are  exposed, 
by  the  heeling  of  the  ship,  grape  or  canister  may  be  used  against 
them,  at  distances  ranging  from  200  to  300  yards.  Against 
light  vessels  a single  stand  of  grape  from  heavy  guns  may  be 
used  at  about  400  yards. 

1713.  liijled  Canister. — It  has  been  believed  that  the  canis- 
ter practice  of  rifle-guns  is  inferior  to  that  of  smooth-bores, 
but  the  comparative  trials  instituted  by  various  countries  prove 
that  the  canister  practice  of  rifle-guns  is  at  least  as  effective  as 
that  of  smooth-bores. 

The  smooth-bore  practice  does  not  usually  extend  beyond 
the  dangerous  fire  of  modern  small  arms,  so  that  generally  at  all 
distances  where  it  can  act  usefully,  the  canister  as  well  as  the 
shrapnel  practice  of  rifled-guns  is  superior  to  that  of  smooth- 
bores. 

1714.  Horizontal  fire  includes  all  kinds  in  which  the  pro- 
jectile strikes  its  object  with  a velocity  due  wholly,  or  nearly  so, 
to  the  charve.  In  this  fire  the  ranges  are  regulated  bv  alteration 
in  the  elevation  of  the  axis  of  the  piece,  a fixed  charge  being 
generally  used  with  each  nature  of  gun  ; this  charge  is  the  lar- 
gest the  piece  is  capable  of  firing,  so  as  to  give  very  high  velo- 
city to  the  projectile,  and  consequently  a low  trajectory,  upon 
which  accuracy  of  fire  and  the  extent  of  ground  effectively 
covered  by  the  projectile  mainly  depend. 

1715.  Vertical  fire  includes  all  kinds  in  which  the  projec- 
tile strikes  with  a velocity  due  wholly,  or  nearly  so,  to  gravity. 


DIFFERENT  KINDS  OF  FIRE. 


621 


The  usual  angle  of  fire  of  mortars  is  4:5  degrees,  ■which  cor- 
responds nearly  with  the  maxiinuni  range.  The  advantages  of 
the  angle  of  greatest  range  are  : 

1st.  Economy  of  powder.  2d.  Diminished  recoil  and  strain 
on  the  piece,  bed,  and  platfonn.  3d.  More  uniform  ranges. 
When  the  distance  is  not  great,  and  the  object  is  to  penetrate  the 
roofs  of  magazines,  buildings,  etc.,  the  force  of  fall  may  be  in- 
creased by  firing  under  an  angle  of  60  degrees. 

The  ranges  obtained  under  an  angle  of  60  degrees  are  about 
one-tenth  less  than  those  obtained  wfith  an  angle  of  4:5  de- 
grees. 

If  the  object  be  to  produce  effect  by  the  bursting  of  the  pro- 
jectile, the  penetration  should  be  diminished  by  firing  under  an 
angle  of  30  degrees. 

When  the  object  and  the  mortar  are  not  on  the  same  level,  the 
angle  of  greatest  range,  instead  of  being  4:5°,  is  4:5°  ± 4-  the 
angle  of  elevation  or  depression  of  the  object.  Thus,  to  reach 
an  object  elevated  15°  above  a mortar,  the  angle  of  greatest 
range  would  be  4:5°  -j-  74"°  = 524-°  ; 'while,  if  the  object  was  de- 
pressed 15°,  the  angle  w'ould  be  15° — 74-°=374-°. 

1716.  The  angle  of  fire  being  fixed  at  15°  for  objects  on 
the  same  level  with  the  piece,  the  range  is  varied  by  varying  the 
charge  of  powder.  The  practical  rule  is  founded  on  the  know- 
ledge of  the  amount  of  powder  necessary  to  diminish  or  increase 
the  range  a certain  quantity. 

The  13-in.  mortar  with  a charge  of  3 lbs.  of  powder  gives  a 
range  of  850  yards,  and  every  additional  4- lb.  increases  the  range 
about  180  yards.  The  elevation  being  15°. 

1717.  A practical  rule  for  finding  the  time  of  flight  by 
which  the  length  of  the  fuze  is  regulated,  is  to  take  the  square- 
root  of  the  range  in  feet,  and  divide  it  by  four  ; the  quotient  is 
the  approximate  time  in  seconds. 

1718.  The  greatest  dilficulty  in  firing  mortars  is  to  regulate 
the  charges  properly  ; very  great  differences  are  found  to  exist 
between  ranges  obtained  under  the  same  circumstances,  and 
these  increase  with  the  range,  whilst  the  lateral  deviations  are 
much  less. 

The  utmost  exactness  is  to  be  observed  in  measuring  and 
filling  the  cartridges,  as  an  ounce  of  powder  makes  an  important 
variation  in  the  range. 

Tables  of  charges,  elevations,  and  ranges  for  the  13-in.  mor- 
tar are  given  in  the  Ordnance  Instructions. 

1716.  To  estimate  the  distance  by  the  bursting  of  the  shell, 
where  the  flames  can  be  seen,  multiply  the  number  of  seconds 


622 


NAVAL  ORDNANCE  AND  GUNNERY. 


that  elapse  hetvveen  it  and  the  report  by  1100,  and  the  product 
will  be  approximately  the  distance  in  feet."  (Art.  1636.) 

1720.  Falliruj  Yelocity. — The  falling  velocity  of  a mortar- 

shell  at  ordinary  range  may  be  found  with  sufficient  accuracy 
for  practical  purposes  as  follows : The  shell  may  be  assumed 

to  be  rising  during  half  the  time  of  flight  and  falling  during 
the  other  half ; therefore,  if  t be  the  time  of  flight,  and  Y the 
velocity  required,  the  latter  will  be  due  to  ; thus,  if  for  500 
yards  t = lO",  Y = gt  .’.  Y = 32x5  = 160  feet. 

1721.  Mortars  afloat  are  usually  not  to  be  much  dreaded ; 
though  mortar-vessels  moored  in  smooth  Avater  may  be  A'ery 
efl'ecti  ve. 

Large  mortars  should  be  used  for  the  defence  of  navy  yards, 
or  other  important  stations  on  the  sea-board  ; for,  although  their 
inaccuracy  of  fire  may  cause  many  shells  to  be  wasted,  the 
chance  of  one  or  tAvo  falling  upon  the  deck  of  any  A’essel  Avould 
usually  prevent  its  coming  Avithin  short  range. 

1722.  Yertical  fire  is  of  all  practice  from  ordnance  the  most 
uncertain  as  regards  precision.  The  chief  causes  of  inaccuracy 
of  Amrtical  fire  are;  that  the  shells  having  comparatively 
low  velocity,  but  long  times  of  flight,  are  peculiarly  liable  to 
considerable  deviation  from  wind  and  other  disturbing  causes ; 
that  the  angles  of  descent  of  mortar  sliells,  fired  at  the  usual 
angle  of  15°,  are  so  great  that  unless  the  object  be  of  some 
extent,  au  error  in  range  of  a feAv  yards  might  render  the  shell 
useless  ; Avhereas,  Avhen  a projectile  is  fired  at  a Ioav  angle  of  ele- 
vation, so  much  ground  is  covered  by  it  before  and  after  grazing 
that  an  error  of  some  yards  xmder  or  over  Avould  not  generally 
be  of  mucli  consequence  ; also,  that  it  is  difficult  in  practice  to 
ensure  the  requisite  care  in  Aveighing  out  the  charges,  or  to  ob- 
tain poAvder  of  uniform  quality.  In  vertical  fire,  as  the  object 
cannot  generally  be  seen,  and  the  piece  is  usually  short,  it  is 
very  difficult  to  point  the  mortar  exactly  in  the  same  line  for  a 
number  of  rounds  ; but  if  the  pointing  could  be  performed 
Avith  the  greatest  accuracy,  irregularities  must  always  occur  in 
practice  Avitli  projectiles  iired  at  high  angles  and  Avith  low  A'elo- 
cities. 

1723.  Saiall-Arai  Firing. — The  fire  of  the  rifle-musket  is 
not  effective  beyond  1200  yards  ; the  angle  of  fall,  howe\'er,  is 
so  great  that  gi’eat  care  must  be  exercised  in  determining  the 
exact  distance  of  the  object.  If  the  ground  be  favorable,  the 


* At  the  temperature  of  33°  the  mean  velocity  of  sound  is  109'2..'5  feet 
in  a second.  It  is  increased  or  diminished  half  afoot  for  each  degree  of  tem- 
perature above  or  below  33°. 


GUN  IMPLEMENTS. 


623 


projectile  M'ill  ricocliet  at  1000  yards,  which  increases  the  dan- 
gerous space,  and  therefore  the  chances  of  hitting  the  object. 

The  limit  of  any  fire  is  determined  by  the  distinctness  of 
vision. 

The  effect  of  small-arm  firing  depends  much  on  the  skill 
and  self-possession  of  the  individual,  for  Avithout  these  quali- 
ties the  most  powerful  and  accurate  arms  will  be  of  little  a\'ail. 


Section  III. — Gun  Implements.'^ 

1721.  Staves. — The  staves  of  all  implements  are  made  of 
tough  ash,  round,  2 in.  in  diameter  for  all  lengths  of  over  150 
in..  If  in.  for  all  other  lengths  above  100  in.,  and  1-|-  in.  for  all 
below.  A tenon  is  made  on  one  end,  f of  an  in.  less  in  dia- 
meter than  that  of  the  staff. 

1725.  Sponges. — The  sponge  complete  is  18  in.  longer  than 
the  bore  of  the  gun  for  Avhich  it  is  intended. 

The  staif  is  2 in.  shorter  than  the 
implement  complete.  The  tenon  is 
If  in.  shorter  than  the  head.  In  the 
end  of  the  tenon  a Avorm  is  secured  by 
means  of  a copper  pin  passing  through 
a hole  in  its  shank  and  the  tenon. 

The  worm,  2 in.  in  length  and  If  in. 
in  diameter,  is  made  of  elastic  compo- 
sition AA'ire  of  in.  in  diameter,  ta- 
pering at  the  points.  It  is  riglit-han- 
ded  in  order  to  act  Avhen  turned  to 
the  right,  or  AA’ith  the  sun.  (Fig.  360.) 

The  sponge-head  is  made  of  poplar 
or  other  suitable  light  wood,  and  for 
smooth-bore  guns  consists  of  a cylin- 
drical body  1 in.  in  length,  surmount- 
ed by  a section  Avhose  surface  is  similar 
to  that  of  the  chamber  of  the  gun. 

This  section  is  fin.  shorter  than  the 
chamber,  and  the  diameter  of  the  head 
at  any  point  is  1 in.  less  than  the  diameter  of  the  chamber,  or 
bore,  at  that  point.  For  unehambered  guns  the  sponge-head 
conforms  in  shape  to  the  bottom  of  the  bore ; the  radius  of  its 
curve  being  f in.  less  than  that  of  the  bore,  the  cylindrical 
body  is  retained. 

* Dimensions  and  Weights  of  Gun  Implements.  Bureau  of  Ordnance,  1874. 


Fig.  360. 


624 


NAVAL  OKDNANCE  AND  GUNNERY. 


length 


1726.  Sponge-heads  for  all  rifled  guns  are  2 calibres  in 
A hole  of  the  size  of  the  tenon  is  bored  througli  the 
axis  of  the  head,  and  the  head  is  secured  to 
the  staff  by  means  of  a copper  pin  in.  in 
diameter,  through  the  cylindrical  body. 
When  the  head  is  properly  fixed  to  the 
staff  it  bears  firmly  against  the  shoulder  of 
the  tenon,  allowing  the  end  of  the  worm  to 
project  in.  (Fig.  361.) 

Sponge-heads  for  greater  calibres  than 
Xlll-in.  smooth-bore  and  Ylll-in.  rifles  are 
built  up,  hollow.  All  sponge-heads,  when 
finished,  are  primed  with  several  coats  of 
boiled  linseed  oil  or  varnish. 

1727.  TAe  woollen  sponge  is  made  of  the 
shape  and  size  requisite  to  tit  the  head,  with 
an  allowance  of  1 in.  in  length  for  tackin2 


1.75 


9. 


length 

over  the  edge  of  the  base.  The  wool 
sheared  so  as  to  allow  no  windaire. 


IS 


Fig.  361. 


Sponge-caps  for  guns  on  covered  decks 
are  made  of  duck,  of  a size  to  tit  the  sponge 
snugly,  lapping  1.5  in.  over  the  base.  The 
mouth  is  fitted  with  a draw-string,  and  a 
becket  is  fitted  to  the  other  end.  These 
caps  are  not  painted  but  kept  scrubbed.  For 
uncovered  guns  and  all  howitzers,  the  sponge- 
caps  are  similar  to  the  others,  except  that  they  are  long  enough 
to  gather  around  the  staff.  Ties  are  fitted  to  secure  them  in- 
stead of  a draw-string ; and  they  are  kept  painted  white.  The 
cap  is  never  put  on  the  sponge  unless  both  are  clean  and  dry. 

1728.  Bristle  sgionge-keads  are  1.5  in.  less  in  diameter  than 
the  chambers  and  bores  of  the  gun  for  which  they  are  intended. 
The  bristles  are  sheared  so  as  to  work  easily  and  leave  no  wind- 
age. Three  spiral  spaces  are  left  the  whole  length  of  the  sponge- 
head,  in  order  to  bring  out  unconsumed  portions  of  cartridge ; 
these  spaces  are  right-handed.  Two-thirds  of  the  head  is  covered 
with  bristles,  one-third  bare  ; the  end  of  the  sponge  is  entirely 
covered  ; there  is  no  worm  in  bristle  sponges. 

1729.  R.:Vmmeks. — The  rammer  complete  is  shorter  than  the 
sponge,  by  the  length  of  the  sponge-head.  The  rammer  staff 
for  smooth-bores  is  ecpial  to  the  length  of  the  complete  rammer, 
minus  one-third  the  length  of  the  head. 

The  rammer-head  for  smooth-hores  (Fig.  362)  is  made  of  ash, 
birch,  beech,  or  other  tough  wood,  and  consists  of  a cylindrical 
body  and  hemispherical  neck.  The  neck  is  struck  witli  a radius 


GU2^  IMPLEMENTS. 


625 


of  2 in.  Tlie  necks  of  raminer-keads  nbove  13  in.  are  cylindri- 
cal, 'vvitli  tlie  same  radius,  and  one-third  the  length  of  the  head. 
The  diameter  of  the  boclj  is  .25  in. 
less  than  that  of  the  hore  ; its  length, 
two-thirds  that  of  the  Avhole  head. 

The  head  of  a 32-pdr.  rammer  is  1 
calibre  in  length.  I'or  every  change 
of  calibre  of  1 in.  there  is  a corre- 
sponding change  of  .25  in.  in  the 
length  of  the  head.  The  rear  of  the 
body  is  bevelled  off  to  the  neck,  in 
a curve  of  1 calibre.  The  front  end 
is  hollowed  ont  vuth  the  same  ra- 
dius, the  bottom  of  the  curve  be- 
ing bevelled  oli  where  it  meets  the 
hole  for  the  staff,  leaving  the  exte- 
rior of  the  hole  2 in.  in  diameter. 

An  annular  sirrface  is  left  around 
the  face  of  the  head,  1 in.  in  width, 
for  calibres  above  Xl-in.  ; .75  in. 


75 

Fig.  362. 

for  all  others.  The  staff  tenon 
is  two-thirds  the  length  of  the  head,  its  shoulder  coming  scpiare 
up  to  the  base  of  the  neck.  The  head  is  secured  to  the  staff 
n by  a copper  pin  .2  in.  in  diameter  through 

the  thickest  part  of  the  neck.  Eamrner- 
heads  for  greater  calibres  than  Xlll-in.  are 
strengthened  by  copper  hands  .5  in.  wide 
around  the  ends  of  the  head  and  neck  ; the 
copper  is  Xo.  IT  American  wire-gauge. 

1730.  Rammer-heads  f 07'  rifled  guns  are 
made  of  composition  (Fig.  363),  cup-shaped, 

1 calibre  in  length,  with  a neck  two-thirds 
the  length  of  the  body,  and  tapering  from 

2 in.  in  diameter  at  the  throat  to  1.75  in.  at 
the  end.  The  extreme  diameter  of  the  head 
is  .25  in.  less  than  that  of  the  bore.  The 
diaplu-agm  between  the  hollow  of  the  head 
and  neck  is  .2  in.  in  thickness.  The  hollow 
of  the  head,  for  a depth  of  1.25  in.,  corre- 
sponds to  the  head  of  the  projectile  in  shape  ; 
the  rest  is  cut  away,  so  as  to  leave  a shell 
.2  in.  in  thickness.  The  head  is  secured  to 
the  staff  by  two  composition  pins  .2  in.  in  dia- 
meter through  the  neck.  Metal  rammer-heads 
for  all  guns  above  Tl-in.  calibre  are  lightened 


kA 

Fig.  363. 


40 


by  having  segments  cut  out  of  the  body. 


626 


NAVAL  ORDNANCE  AND  GUNNERY. 


1731.  Ladles. — The  ladle  complete  is  of  the  same  length  as 
the  rammer.  The  staff  and  head  are  of  the  same  dimensions, 
except  the  length  of  the  staff,  which  is 
calibres  shorter  than  the  rammer-staff. 
(Fig.  361.) 

The  diameter  of  the  head  is  reduced 
(to  make  a seat  for  the  scoop)  1 in.  in 
length  for  calibres  above  Xl-in.  ; 3 in. 
for  all  others.  The  scoop  is  secured  to 
the  head  by  two  rows  of  copper  tacks. 
The  copper  used  for  making  scoops  is 
Xo.  11  for  calibres  above  Xl-in.,  Xo.  13 
forXI-in.  and  IX-in.,  Xo.  15  for  Ylll-in. 
and  32-pdr.,and  Xo.  IT  for  all  howitzers 
(American  wire-gauge). 

1732.  IVoRMS. — The  worm  complete 
is  the  same  length  as  the  rammer.  (Fig. 
365.)  The  head  consists  of  a round 
composition  shaft,  having  a worm  2 in. 
in  length  at  one  end,  and  two  straps  8 
in.  long  at  the  other,  the  total  length  be- 
ing 20  in.  At  8 in.  from  the  end  of  the 
worm  is  a shoulder,  for  a disc  of  compo- 
sition .25  in.  less  in  diameter  than  the 
bore  for  which  it  is  intended.  It  is  kept 
in  its  place  by  a key.  The  staff  fits  into 
a socket  formed  by  the  straps,  and  is 
kept  in  place  __ 


Fig.  364. 


by  two  compo- 
sition pins  pas- 
sing; througli 
both  straps. 
Staves.  — The 
casemate 


ffuns. 


1733.  Sectional 
staves  for  turret  and 
where  stoppers  and  shutters  are  used, 
are  sectional,  with  spring  connecting 
joints.  (Fig.  366.)  One  section  is 
permanently  fixed  to  the  head  of  the 
implement,  projecting  12  in.  beyond 
its  base.  As  the  length  of  the  imple- 
ment is  arbitrarily  fixed,  by  the  neces- 
sity of  having  a certain  amount  of  staff 
beyond  the  end  of  the  bore  when  the 
implement  is  home,  one  length  is  made 
longer  or  shorter  than  the  average,  ac- 


I 


1 1 iiiha 


/4.  75 


Fig.  365. 


GUN  IMPLEMENTS. 


627 


cording  to  necessity.  All  other  sections  are  36  in.  long  exclu- 
sive of  the  tenons,  which  are  3 in.  in  length,  a corresponding 
socket  being  fitted  in  the  other  end  of  the  section.  All  detacha- 


36" 

1 r;::;]: 

^///////^//^ 

36" 

1 ° i 

36  " 

' 1 r— -1: 

' Fig.  366. 


hie  sections  are  interchangeable.  Each  gun  is  supplied  with 
three  of  the  36-in.  sections.  These,  together  with  the  fixed  and 
odd  sections,  make  the  length  of  the  different  implements. 


CHAPTEE  XL 


THE  MOTION  OF  PROJECTILES. 


173L  A knowledge  of  the  motion  of  projectiles  in  a non-re- 
slstinj  medium  is  useful  as  an  introduction  to  the  discussion  of 
the  inotion  of  projectiles  in  air;  the  following  iiivestigation,  in 
which  the  resistance  of  the  air  is  not  considei'ed,  is  therefore  in- 
troduced here.  The  attraction  of  gravitation  is  assumed  to  be 
constant  and  parallel  to  a fixed  line. 

The  Equation  of  the  Path  of  a Projectile  in  a Xon- 
REsiSTiNO  Medium. — Let  the  origin  he  taken  at  the.  point  of 
projection,  and  let  the  axis  of  y be  vertical,  and  that  of  x hori- 
zontal and  in  the  plane  of  projection  ; x and  y are  the  current 
co-ordinates  of  the  centre  of  gravity  of  the  projectile.  It  is 


evident  that  this  point  will  continue  to  move  in  the  plane  xy, 
as  it  is  projected  in  it,  and  is  subject  to  no  force  tending  to 
withdraw  it  from  that  plane,  u denotes  the  initial  velocitv,  a 
the  angle  of  projection,  and  t the  time  reckoned  from  the  in- 
stant at  which  the  projectile  starts  from  0. 


Y 


0 


Fig.  367. 


* By  Professor  J.  M.  Rice,  United  States  Xavy. 


THE  MOTION  OF  PROJECTILES. 


629 


Tlie  equations  of  motion  are 


d'x 

df 


and 


d^ 

df 


ac2eleration  parallel  to  tlie  axis  of  cb  = 0 (1), 

acceleration  parallel  to  tlie  axis  of  y = — ^ . .(2). 


Integrating  equations  (1)  and  (2),  we  obtain 

= constant  = cos  a. 
dt 

and  = constant  — sin  a — gt (3). 

Integrating  again, 

X = ti  cos  a.t (4),  and  y = u sin  a.t  — ^ gf (o). 

Eliminating  t between  (4)  and  (5),  we  obtain  the  equation  of  the 
path  or  trajectory 

2/  = £B  tan  a — ^ j— (a) 

2 u cos  a ^ 

or,  putting  li  = , 

X' 

y = X tan  a — s— (6), 

^ 4A  COS'  a ^ 


h is  evidently  the  height  from  which  a body  must  fall  to  ac- 
quire the  velocity  u.  {b)  is  the  form  in  which  this  equation  is 
usually  employed.  It  is  evidently  the  equation  of  a parabola. 


To  FIND  THE  Vertex  of  the  Trajectorv'. 

1735.  Multiplying  (b)  by  4A  cos'’  a and  transposing,  we  have 
X'  — 4/i  sin  a cos  a.  x = — 4/i  cos^  a.y. 

Completing  the  square  by  adding  4A'’  sin'  a oof  a,  we  have 

{x  — 2/i  sin  a cos  df  = 4A'  sin'  a oof  a — - 4A  cos’  a.y, 
or  (x  ■ — A sin  2 af  = 4A  cos’  a (A  siir  a — y). 

If  we  pass  to  a new  system  of  co-ordinate  axes  parallel  to 


630 


NAVAL  ORDNANCE  AND  GUNNERY. 


the  old,  by  patting  x^  — x — h sin  2 a,  and  y,  = h sin'^  a — y,  we 
obtain 

— 4A  cos'*  a.y„ 

the  equation  of  a parabola  referred  to  the  vertex  and  principal 
axes.  Tlie  co-ordinates  of  the  new  origin,  which  is  also  the 
vertex,  are 

x^  — x — a?,  =:  A sin  2a (6), 

and  = y = h sin'* a (see diagram).. . . (7). 

Since  the  curve  is  symmetrical  with  reference  to  S2l,  OR, 
which  is  called  the  range  on  a horizontal  plane,  is  equal  to  2x^ ; 
but 

2a?„  = 2A  sin  2a  = ^ (8), 

R denoting  the  range. 

2A  sin  2a  is  a maximum  when 

2a  = ^,  or  a = y or  45°. 

That  is,  the  greatest  range  is  obtained,  when  the  angle  of  ele- 
vation is  45°  ; its  value  is  2A,  and  the  corresponding  maximum 

height  is  [see  equation  (7)].  When  a is  45°,  the  range  is 

2i 

therefore  four  times  the  greatest  height. 

Again,  since 

sin  2a  = sin  (180°  ■ — 2a)  = sin  2 (90°  — a), 

the  complement  of  any  angle  gives  the  same  range  as  the  angle 
itself. 


To  FIND  THE  TeVIE  OF  FlIGHT  OF  A PrOJECTFLE  ON  A HORI- 
ZONTAL PLxVNE. 

1736.  To  find  the  time  of  flight,  we  divide  the  range 
[2A  sin  2a]  by  tlie  hoiizontal  velocity  \u  cos  a]  thus, 

2A2sinacosa  4Asina  2 sin  a 

t = = (9). 

?fcosc  u g ^ ' 

This  equation  gives  the  time  of  flight  in  terms  of  u and  a ; 
to  obtain  t in  terms  of  R and  a,  which  is  sometunes  desii’ahle. 


THE  MOTION  OF  PROJECTILES. 


631 


we  put  a?  = and  y =:  0 in  equations  (4)  and  (5),  wliicli  then 
become 

R — u cos  a.  t and  0 =w6\na.t  — ^ gf. 


Eliminating  u,  we  obtain 

R tan  a,  = ^ gf^ 


or 


R tan  a 
9 


(10). 


, 173Y.  To  FIND  THE  Elevation  necessary  to  cause  the 
Trajectory  to  pass  through  a Point  given  by  its  Co-or- 
dinates x'  AND  y',  THE  INITIAL  YeLOCITY  BEING  GIVEN. 

x'^ 

We  have  y'  = x'  tan  a — 77 7-,  to  find  tan  a : 

^ 4A  cos  a ’ 

putting  tan  a = z,  we  have 

— ^ ^ sec'’  a = 1 -I-  tan'’  a = 1 4-s'’ ; 
cos  a ' ‘ ’ 

substituting  in  the  above  equation,  it  becomes 


or 


2 44  4A  , 


4A^  4Ay' 


4Ay'  — 


^ ^h^  — ^hy'—x'^ (11). 

If  y'  and  x'  have  such  values  as  to  make 
4:hy'  -f-  x'"‘  < 4A* 
there  will  be  two  real  values  of  z,  but  if 
4Ay'+»'“>  4A’ 

the  values  of  z will  be  imaginary ; in  this  case  it  is  therefore  im- 


632 


NAVAL  ORDNANCE  AND  GUNNERY. 


possible  to  so  change  a as  to  make  the  trajectory  pass  through 


the  point. 

If  (12), 

tliere  will  be  one  real  value  of  z. 

Making  x'  and  y’  variables  in  ecpiation  (12),  we  have 

= 44=  _ = 44  (A  _ (1.3), 


the  ecpiation  of  a parabola  having  its  vertex  on  the  axis  of  y at 
the  height  4 above  the  origin. 

Since  the  co-ordinates  of  any  point  in  this  curve  will  give, 
when  substituted  in  equation  (11),  a single  value  of  2,  all  the  tra- 
jectories thus  formed  totich^  but  clo  not  cut  the  curve  of  ecpia- 
tion (13) ; this  curve  is  called  an  envelop. 


1738.  To  FIND  THE  Yelocity  of  a Projectile  at  any  Point 
OF  its  Path. 


We  have  (|)  = ()|)  + 


3-  If 

substituting  the  values  of  and  from  equations  (3)  we  de- 


duce 


qf  — COS'  a -|-  [it  sill  a — gtf  ; 
expanding  and  reducing 


— u‘  — 2y  (lit  sin  a — ^gf), 
therefore,  by  equation  (5),  v'  — tt"  — 2yy. 

If  we  put  for  its  value  2y4,  we  obtain 

v"  = 2g  {h  -y) (14). 


1739.  To  FIND  THE  DIRECTION  OF  THE  PATH  AT  ANY  POINT, 
we  differentiate  equation  (b);  thus 


dy 

dx 


= tana 


24  cos^  a 


— tan  c6 


(15), 


0 being  the  angle  of  inclination  of  the  curve  to  the  axis  of  x. 


THE  MOTION  OF  PROJECTILES. 


633 


dy 

Putting  ^ = 0,  Ave  have  x = 2/i  sin  a cos  a — h sin  2a,  for 

the  abscissa  of  the  summit,  or  highest  point  of  the  path.  The 
corresponding  value  of  y is 

h sin“  a. 


which  is  therefore  the  greatest  height  the  projectile  attains  ; it 
is  also,  as  might  have  been  aiiticipated,  the  ordinate  of  the  ver- 
tex ; see  equation  (7). 

IT-iO.  To  FIND  TiiE  Co-ordinates  of  the  Point  where  a Pro- 
jectile WILL  STRIKE  AN  INCLINED  PlANE  PASSING  THROUGH  THE 

Point  of  Projection,  the  Range  on  the  Inclined  Plane,  and 
THE  Time  of  Flight. 

Let  y—x  tan  (3  be  the  equation 
of  the  line  OP,  which  is  the  inter- 
section of  the  inclined  plane  with 
the  vertical  jilane  of  the  path  of 
the  centre  of  gravity  of  the  body. 

0 

FIG.  368. 

Let  a?,  and  y,  be  the  co-ordinates  of  P,  and  let  OP—r,  the 
range ; then 

X,  = r cos  13  and  y,  — r sin  /3. 


Substituting  in  equation  («)  we  have 

. _ r'cos"/? 

r sin  [3  = r cos  f3  tan  a — ^ 5 — : 

•lAcos  a’ 


whence  r — 0,  ov  r — 


and  reducing  r — 


r cos  (3  — X,— 
and  r &in  (3  = y, 


4A  cos°  a (cos  f3  tan  a — sin  f3) 
cod  (3  ^ 

4/i  cos  a sin  (a  — ff) 


cod  (3 

47;  cos  a sin  (a  — (3) 
cos  (3  ’ 

4/t  COG  a sin  /3  sin  (a  — [3) 
cos^  (3 


(14), 


634 


NAVAL  ORDNANCE  AND  GUNNERY. 


If  the  inclined  plane  cnt  the  path  of  the  projectile  below  the 
axis  of  £c,  (3  will  be  negative. 

The  time  of  flight  is  found  by  dividing  by  u cos  a,  the  hori- 
zontal component  of  initial  velocity  ; thus, 

4A  cos  a sin  (a  — j3) 

~ u cos  /3  cos  a ’ 


putting  for  h its  value  — and  reducing, 

2wsin  (a  — S') 

t = (15). 

(J  cos  p ^ ’ 

1741.  The  resistance  of  the  air  to  the  motion  of  spherical  solid 
shot  evidently  increases  with  the  square  of  the  diameter,  while 
the  weight  of  the  shot  is  proportional  to  the  cube  of  the  diame- 
ter. This  resistance  is  therefore  less  effective  with  large  spherical 
shot  than  with  small  shot ; but  it  is  nevertheless  so  considerable, 
even  in  the  case  of  the  heavy  shot  now  in  use,  as  to  render  the 
above  formulas  inapplicable  in  practice,  except  to  cases  of  low 
initial  velocities  not  exceeding  400  ft.  per  second.  It  increases 
rapidly  with  the  velocity,  being  nearly  proportional  to  the  cube. 

1742.  Equations  (8),  (9),  and  (10)  are  sometimes  used  in  mor- 
tar practice.  If  in  equation  (10)  we  put  ^=32  ft.,  we  have  ap- 
proximately 

t = ^ \/E  tan  a (16). 

If  a is  45° 

t = (17). 

Example  10  will  serve  to  show  that  the  results  obtained  by 
these  formulas  are  sufliciently  accurate  for  some  purposes,  when 
the  velocities  are  small.  The  charge  of  powder  used  in  the  ex- 
periments which  furnished  the  data  of  Ex.  10,  was  a little  less 
than  two  pounds  in  the  flrst  case,  and  a little  more  than  two 
pounds  in  the  second  case.  The  following  example,  taken  from 
Owen’s  2rodern  Artillery,  will  show  how  entirely  untrust- 
worthy these  formulas  are  in  the  eases  of  ordinary  practice. 

The  range  of  a 32-lb.  shot,  tired  with  an  initial  velocity  of 
1600  ft.,  and  with  an  angle  of  elevation  of  4°,  was  5070  ft. ; as 
comjjuted  by  formula  (8)  it  should  be  11,130  ft. 


THE  MOTION  OF  PROJECTILES. 


635 


Examples. 

1.  The  horizontal  range  of  a projectile  is  1000  ft.  and  the 
time  of  flight  is  15  seconds.  Eequired  tlie  angle  of  elevation, 
velocity  of  projection,  and  greatest  altitude. 

Ans.  a =:  74°  33' 09". 

V = 250.29  ft. 

II  = 904.69  ft. 

2.  Find  the  velocity  and  angle  of  elevation  of  a ball  that  it 
may  be  100  ft.  above  the  ground  at  the  distance  of  one  quarter 
of  a mile,  and  may  strike  the  ground  at  the  distance  of  one 
mile. 

Ans.  a = 5°  46'  05. 

V = 921.566  ft. 

3.  What  must  be  the  angle  of  elevation  of  a body  in  order 
that  the  horizontal  range  may  be  equal  to  three  times  the  greatest 
altitude  ? What,  that  the  range  may  be  equal  to  the  altitude? 

4.  A body  is  projected  at  an  angle  of  elevation  of  60°,  with 
a velocity  of  150  ft. ; And  the  co-ordinates  of  its  position,  its 
direction,  and  velocity  at  the  end  of  5 seconds. 

5.  A body  is  projected  from  the  top  of  a tower  200  ft.  high, 
at  an  angle  of  elevation  of  60°,  with  a velocity  of  50  ft.  ; And 
the  range  on  the  horizontal  plane  passing  through  the  foot  of 
the  tower,  and  the  time  of  flight. 

6.  A body,  projected  in  a direction  making  an  angle  of  30° 
with  a plane  whose  inclination  to  the  horizon  is  45°,  fell  upon 
the  plane  at  the  distance  of  250  ft.  from  the  point  of  projection, 
which  is  also  in  the  inclined  plane ; required,  the  velocity  of  pro- 
jection and  the  time  of  flight. 

7.  At  what  elevation  must  a shot  be  fired  with  a velocity  of 
400  ft.  that  it  may  range  2500  yards  on  a plane  which  descends 
at  an  angle  of  30°  ? 

8.  Find  the  velocity  and  angle  of  elevation  that  a projectile 
may  pass  through  two  points  whose  co-ordinates  are  a?=300  ft., 
yr=60  ft.,  a?'=400  ft.,  and  y'=40  ft. ; also  find  the  horizontal 
range,  greatest  altitude,  and  time  of  flight. 

9.  Show  that  the  maximum  range  on  an  inclined  plane,  of  a 
projectile  having  a given  initial  velocity  w,  is  — 

in  which  (3  denotes  the  inclination  of  the  plane  to  the  horizon. 


636 


NAVAL  ORDNANCE  AND  GUNNERY. 


10.  The  observed  time  of  flight  of  an  8-in.  mortar  shell  was 
16*.0.  the  range  being  3760  ft.,  and  the  angle  of  elevation  4:5°  ; 
find  the  difference  between  this  observed  range  and  that  obtained 
by  computation  Avhen  the  formulas  of  the  preceding  articles  are 
employed.  Find  the  difference  when  the  range  was  5S79.4:  ft., 
ancl  the  observed  time  20b8. 

Ans.  —0.7  and  —1.6. 


The  Motion  of  a Projectile  in  Air. 

1743.  A complete  and  satisfactory  solution  of  this  problem 
has  not  hitherto  been  published  ; in  fact,  the  laiv  of  resistance  of 
the  air,  which  must  be  found  by  experiment,  is  not  yet  fully 
established. 

Some  recent  experiments  made  in  England  by  Professor 
Francis  Bashforth  show  that  the  resistance  of  the  air  to  the  mo- 
tion of  a projectile  is  approximately  proportional  to  the  cube  of 
its  velocity.  The  direction  of  the  resistance  of  the  air  at  any 
point  of  the  path  of  a projectile  is  evidently  that  of  a tangent 
to  the  path  draivn  through  the  point. 

The  following  mathematical  investigation  is,  with  some 
changes  in  the  notation,  substantially  that  of  Professor  Bash- 
forth, and  the  accompanying  tables  which  ivill  be  found  in  the 
appendix  to  this  work  are  reprinted  from  his  treatise"  ; by  means 
of  these  tables  the  trajectory  of  a projectile  and  its  time  of  flight 
may  be  approximately  found. 

1744.  R denoting  the  resistance  of  the  air,  and  P the  I'elo- 
city  of  the  projectile,  the  cubic  laiv  of  resistance  is  expressed 
thus — • 

R = ^l  T\ 

In  this  expression  % is  a cpiantity  to  be  determined  by  ex- 
periment; it  is  not  the  same  for  all  Auilues  of  P,  and  has  there- 
fore been  tabulated.  The  following  notation  is  adopted  for  the 
pui’pose  of  simplifying  the  formulas  : 

Let  u denote  the  horizontal  component  of  the  velocity,  v the 

* A Mathematical  Treatise  on  the  Motion  of  Projectiles,  founded  chiefly  on 
the  Results  of  Experiments  made  icith  the  Author’s  Chronograph.  By  Francis 
Bashforth,  B.D.  Aslier  & Co.,  Loudon,  1873. 


THE  MOTION  OF  PROJECTILES. 


637 


vertical  component,  and  </>  tlie  inclination  of  the  curve  to  the 
axis  of  cc, 


then 

u — V cos  (j),  and  -y  — sin  </> 

(1) 

Eliminating  V, 

and  'wi’itingy*  for  tan 

we  have 

^ = tan0  =^; 

to 

(2) 

differentiating, 

, tidv  — vdti 



(3) 

Again,  squaring 

and  adding  equations  (1), 

y — tt"  -\-v”  — td  (1  + a') 

(i) 

The  equation 

s of  motion  are,  in  this  case. 

d'x  du  0 7 1^3 

— — 2hV^cos(b 

df  dt 

(5) 

and 

d'y  dv  m TTa  ■ s 

^-^--25Fsin<^-y.. 

(6) 

which  may  be  written  thus — 

^ _ 25  Vht 

dt 

(7) 

and 

d'V  -r7~2 

, - — — V V — q 

dt  ^ 

(8) 

Eliminating  V, 

ndv  — vdu 
dt  - 

hence 

1 

11 

1 

or  [equation  (3)] 

dt 

S' IT 

(9) 

Combining  equations  (7)  and  (d), 



(10) 

and,  eliminating  dt  between  (9)  and  (10), 

638 


XAVAL  ORDNAXCB  AND  GUNNERY. 


This  equation  involves  but  two  variables,  and  is  readily  inte- 
grated. Denoting  by  the  value  of  u corresponding  to  ^ = 0, 
or  in  other  words  the  velocity  at  the  highest  point  of  the  curve, 
and  integrating,  we  obtain 


or 


therefore  1 = i { 1 - ^(3j,  +^)  * 


Putting 


r 


a ’ 


1 

u 


(11) 


(12) 


but  [equation  (9)]  ^ 

therefore,  eliminating 


or 


dt 


u,  dp 


t 


(11) 


. . dx 

Again,  dividing  equation  (13)  by  the  identity  u — 


THE  MOTION  OF  PROJECTILES. 


639 


we  obtain 


'IC' 


dp 

gdx 


, or  dx 


and,  substituting  tlie  value  of  obtained  from  (12),  and  inte- 
grating, we  have 


x=  — 


Jp 


dp 


jy  ll-r(3i^+y)} 


.(15) 


(15) 


Also,  by  means  of  the  identity  dy  — pdx,  we  obtain  from 


y=- ^ 


>i> 


pdp 


.(16) 


2^  \i  ^ 

The  quantity ^ for  “which  y is  substituted  in  equation 

^1)77X>\C  ^ 

(12)  may  be  written  thus, ; the  numerator  denoting  the 

resistance  of  the  air  at  the  vertex  of  the  trajectory,  and  the  de- 
nominator the  weight  of  the  shot. 

Putting  tan  — p and  tan  — p' , 

dp  — sec"  (j)  d<i>  = {l-\-  p^)  d<p  ; introducing  this 
value  of  dp  in  equations  (14),  (15)  and  (16),  and  changing  limits, 
we  obtain 





/ 


4>' 


(1  +y)  d0 


^ p 

~ g y 


X — — 


(1  +y)  d0  _ _ V y 


^ '0 


y^-—  / (p  +p°) __ 

^ J 0 (^P  +P')>  ^ ^ 


] 

] 

] 


<t> 

4>' 

9 

<P' 


(a) 


(^) 


(^) 


640 


NAVAL  ORDNANCE  AND  GUNNERY. 


1745.  Inasimicli  as  it  is  im^Dossible  to  find  the  values  of  x 
y and  t hy  direct  integration,  it  has  been  necessary  to  com- 
pute by  cpiadratnres  the  values  of  X,  I"  and  T for  all  practical 
values  of  -|-  6 not  greater  than  60“,  and  of  — </>  not  less  than 
60°  or  45°,  for  values  of  y = 0.00,  0.01,  (i. 02.. .0.18,  O.iO,  0.2, 
0.3,  0.4... 4.9,  5.0.  The  value  of  d<^  generally  used  Avas  the  cir- 
cular measure  of  1°,  but  Avhen  1 — y (3yj<  became  small, 

the  successive  values  of  — ; — ^ Avere  subiect  to  rapid 

i-r(3i^+y)  ^ ^ 

variation ; in  such  cases  intervals  of  ^°  Avere  used,  and  the  re- 
sults have  been  given  in  preliminary  tables  (see  Appendix).  By 
the  ordinary  rule  of  proportional  parts,  or,  Avhere  great  accuracy 
is  rerpiired,  by  interpolation,  it  Avill  not  be  difiicnlt  to  find  the 
values  of  X,  Y,  and  T for  A'alues  of  y and  (p  intermediate  to 
those  given  in  the  tables. 


Examples  of  the  Methods  of  finding  the  Xumerical 
YaLUES  of  X,  Y AND  T,  y being  GIA'EN. 

From  the  tables,  page  71,  Appendix: 


X ~\'°-X  T=  .20430  - .09348  = .11082, 

0.7  Jo  0.7  Jo 

r T - Y T=  .013448  - .002299  = .011149, 
“■’J.O  “•■’J4 

.11027,  r T = .07836. 


Suppose  it  Avas  required  to  find  the  value  of 


=A]>(u.]; 


X 0.41, 


= .004059  + (.006548  — .005196)  X 0.41 
= .004059  + .001352  X 0.41 
= .004059  + .000554 
= .004613. 

In  the  same  Avay  X^  ^ J 

* In  tills  example  both  limits  are  negative. 


and  T may  be  found. 

3.2  J 3 


THE  UOTIOH  OF  PEOJECTILES. 


641 


1716.  In  order  that  the  tables  may  he  nsed  for  the  solution  of 
problems,  we  see  from  the  above  examples  that  y must  first  be 
determined  numerically*  having  found  its  value,  we  turn  to  the 
corresponding  table,  and  obtain  [see  Fig.  369] 

OM=^  X 1“  JIA  = ^ r 1“ 

g yjo’  g /Jo 

and  the  time  in  OA  = ~ T , for  the  ascending  branch. 


Kow  for  the  descending  branch  we  have  for  the  co-ordinates 
of  the  point  P' , where  the  direction  of  the  curve  is  inclined  at 
an  angle  /3  to  the  horizon,  /3  being  negative. 


an'  =^Xy 
g y J 


^ , N'P'  = ^ X/ 
0 g 1 


and  the  time  in  AP'  = — X/~l^  . 

g r Jo 

To  FLXD  THE  RaNGE  OX  A HoKIZOXTAL  PlAKE. 

/ 


A N 


Having  computed  OM,  we  make  A2£  = N'P',  whence 


By  the  help  of  the  tables  /3  can  be  found,  and  this  value  of 
/3  must  be  used  in  calculating  2Ip. 

Suppose  it  were  required  to  tind  the  height  at  which  the 
shot  would  strike  a vertical  target  placed  at  the  distance  OL, 
and  the  time  of  flight.  Here  we  have 

See  article  1748. 


41 


642 


NAVAL  ORDNANCE  AND  GUNNERY. 


ML^  LO  - OM  xy , 

g rJo’ 

f = (ZO-OJ^)A, 

wliich  gives  (3  by  the  help  of  the  tables.  The  value  of  /3  so 
found  must  be  used  to  hnd  X'P',  whieh  subtracted  from  AJ/, 
computed  by  the  formula  on  page  641,  gives  the  required  height. 
W e must  proceed  in  the  same  way  if  it  be  required  to  Hnd  where 
the  shot  wdll  be  at  a given  time. 

may  be  obtained  by  putting  (p  = a in  equation  (19)  below  (a 
denoting  the  angle  of  projection) ; replacing  and  substituting 
the  value  of  -jq,  we  can  obtain  from  the  same  equation  the  value 
of  U(j,  {(p  being  known  or  assumed). 

1747.  Functions  belonging  to  the  descending  branch  are 
usually  distinguished  from  those  belonging  to  the  ascending 
branch  by  a prime  ; thus,  cp'  denotes  the  angle  made  by  the  de- 
scending branch  of  the  curve  with  the  horizontal  plane. 

The  symbol  f-s  is  sometimes  used  to  denote  feet  j)er  se- 
cond. 

The  relation  between  the  horizontal  component  of  the  velo- 
city and  the  corresponding  velocity  in  the  curve  is  expressed 

thus  : cos  (p  — 


or 


X 


and,  consequently  (a  being  the  angle  of  projection,  and  ^ the 
initial  velocity), 

V cos  a = u. 


1748.  To  DETERMIXE  y. 

2hu  ’ 

We  have  y = — ^ (by  definition,  page  639) ; (17) 


Now,  it  is  obvious  that  b must  increase  directly  with  the  trans- 
verse section  of  the  projectile,  and  inversely  with  its  weight ; 

that  is,  it  must  be  proportional  to  — , c denoting  the  calibre  of 

the  projectile;  we  therefore  put 


THE  MOTION  OF  PROJECTILES. 


643 


% 


=^s(»y 


in  which  K has  been  determined  experimentally  for  snch  ve- 
locities as  are  likely  to  occnr  in  practice ; the  factor  is 

introduced  to  save  space  in  printing  the  tables. 


From  equations  (11)  and  (18)  we  obtain  by  eliminating  25 
1 _ 


1 3 tan  0 -j-  tanV 

u,“  uj  ' gw  (1(JOO)“ 


(19) 


or 


/loooy 

fiooox 

\ w J ~~ 

V u,  ) 

«/> 


K £= 
g'  ^ 


.(20) 


and  introducing  the  value  of  from  (20)  in  (12)  and  reducing, 
we  have 


K ^ 

g_^ 

{ ) -\ . — (3  tan  0 — tan  ^) 

\ / g w ^ 


.(21) 


X. 


Loir  — is  found  in  Tables  I and  II,  and 

g 

Log  (3  tan  (p  + tan®  (f>)=  Log  in  Tables  III  and  Y. 


Examples. 

1749.  A 16-pounder  fires  an  ogival-headed  shot  16  lbs.  in 
weight  and  3.54  in.  in  diameter,  the  angle  of  projection  being 
2°,  and  the  initial  velocity  1358  ft.  per  sec.  ; find  the  trajectory 
and  time  of  flight. 


Putting  IF  = , and  = (3  tan  </>  -j-  tan®  (p),  (21)  be- 


comes 


644 


NAVAL  ORDNANCE  AND  GUNNERY. 


1000 


Kc^ 

g • to 


--P. 

g w 


u^  = u^  = Y cos  2°  = 1358  cos  2°, 
w = 16  lbs.,  and  c = 3.54  in. 


1.358  ar.  co.  9.86710 
2°,  sec  10.00026 


(22) 


Log  9.86736 


=0.40002 3 Log  9.60208 


{v  = 1358) Log  0.51793  (Table  I.) 


K 
9 

c = 3.54 2 Log  1.09800 

ar.  CO.  8.79588 


w = 16 

K 

— ■ - Log  0.41181 Log  0.41181 

g V)  ^ ° 

P,  (Table  III.) Log  9.0203S 

0.27051 


Log  9.43219 


/loop ' ^ 

V ) 


0.67053 Log  9.82642 


y - 3.85 Log  0.5S539 

The  value  of  — (for  v = 1358),  employed  in  the  above 

computation,  is  too  small ; a more  accurate  result  may  be  ob- 
tained by  taking  the  value  corresponding  to  the  mean  of  the 
initial  velocity  (1358),  and  the  value  of  obtained  from 

Loi 


( 1000  \ = 

I I found  above,  thus  : 

V -Wo  / 

Io,(i^)-=0.S.6., 


THE  MOTION  OF  PROJECTILES. 


645 


whence  = 1143  ; hut  u^— 1357 
i ("^^0+  '^2)  = 1250  ; 

corresponding  correction  of  Log  — = -|-  0.01077. 

K & ^ 

— . - (1250) Log  0.42258 

g w ^ ^ ° 

0.27730 Log  9.44296* 

/1^0\  ^Q_4QQQ2 


0.67732 Log  9.83079 


y = 3.91 0.59179 


. - 

= 1139. 

X 

1 = 0.04118, 

and  X 

\^x'  = 

yY 

.X 

1 = 1659.7  ft. 

3«S 

-Jo 

- 

Jo 

<J 

3<9 

J 0 

r 

1 = 0.00076, 

and 

f =2/'  = 

-Y 

1 = 30.67  ft. 

2.9. 

Jo 

9 

3.9- 

J 0 

T 

1 = 0.03788, 

and  t 

2 

T 1 

eo 

r-< 

II 

S.9. 

J 0 

J 

0 

9 

3*9^ 

1 0 

1750.  For  the  descending  branch,  suppose  we  wish  to  find  the 
co-ordinates  of  the  point  at  which  the  curve  makes  an  angle 
of  2°.4  with  the  axis  of  x,  and  suppose  that  by  a rough  compu- 
tation it  has  been  found  that  the  mean  velocity  is  about  1080  ft. 
per  sec. 


From  ecpiation  (22)  we  have 


_ K c-  ( u,  Y 
g’  w VlOOO/ 

3 Log  0.16921 

2 Log  1.09800 


w . ar.  CO.  8.79588 

— (1080) Log  0.50680 

ff  

7 = 3.714 0.56989 

* Obtained  by  adding  correction  to  9.43219. 


646 


NAVAL  OEDNANCE  AND  GUNNEEY. 


.-.X  T = 0.03670,  = x"=:  1479.2  ft. ; 

3.TJ2.4  Js.4 

T T = -0.000737,  yT  = 29.70  ft.; 

3.7J2.4  -J2.4 

T T = 0.03920,  = t"  = 1".387. 

3.7— I 2.4  — 12.4 

= 1002.3  f-s. 

The  point  of  projection  being  tlie  origin,  and  x and  y the  co- 
ordinates of  the  centre  of  gravity  of  the  projectile,  and  t the 
time  wlien  it  is  moving  in  the  descending  branch  of  its  trajec- 
tory in  a direction  inclined  to  the  horizon  at  an  angle  of  2°.4, 
we  have 

a;  = »'  + = 3138.9  ft. 

y = y'  + y"=  0.97  ft. 

^ 2".727. 

Tlie  velocity 

= ^'2.4=  4 sec  2°.4  = 1002.3  see  2°.4  = 1003.2  f-s. 

The  range  on  the  horizontal  plane 

— (3138.9  -)-  0.97  cot  2°. 4),  nearly. 

1751.  A projectile  3.24  in.  in  diameter  is  discharged  from  a 
16-pdr.  with  a velocity  of  1307y-6'/  to  lind  u'„  ^,  v'„  ^,  x,  y, 

and  t / the  values  of  — and  x being  the  same  as  in  the  preced- 
ing example. 

= 1136.5,  u'„  ^ = 1018.6,  tj'„.4  = 1019.5, 

» = 3101,  y=  — 1.09,  ^ = 2".715. 


A spherical  shot  8.9  in.  in  diameter,  and  weighing  94  lbs.,  is 
discharged  with  an  initial  velocity  of  1564  f-s,  the  angle  of 
elevation  being  5° ; find  'ii\,  v\,  x,  y and  i,  the  mean  value 

of  — being,  for  the  ascending  branch  that  corresponding  to  a 

velocity  of  1300  and  for  the  descending  bz*anch  that  coiTe- 
spondiiig  to  900  jfi-.?. 

u,  = 920.5,  a-,  6343',  y,  = 3'.3. 


THE  MOTIOH  OF  PEOJECTILES. 


64T 


To  FEsX)  THE  EaISTGE  ON  A IIoEIZONTAL  PlANE. 
4>  denoting  the  angle  of  incidence,  vre  hare 

i:=^]r”p]:=por- 


V 

In  the  above  example,  y = 3.017  and  y'= 2.822, 
1 


also 

hut  Y — Y 

2.622_Jo 

and  Y 1'= 

2.822_|o  2.822— I 0 

= 8° 


°=  0.006910  = Y'  1*^, 

5 2.822  Jo 

= 0.008329  - 0.006788  = 0.001511, 
0.000122. 


122’ 


— 8°. 079  the  angle  of  incidence, 
loll  * 


Bangs  = x 


+ a?' 


= 3559.7  + 2801.9  = 6361.6. 


In  a similar  manner  rre  obtain  time  of  flight  = 6". 58. 


1752.  A more  accurate  solution  of  the  problem  mar  be  ob- 
tained by  dividing  each  branch  of  the  trajectory  into  successive 
portions,  and  using  a mean  approximate  A’alue  of  K for  each  por- 
tion ; the  final  values  of  a?,  y and  t will  each  be  equal  to  the 
algebraic  sum  of  the  corresponding  partial  values  thus  obtained.. 
It  will  be  convenient  to  change  K at  points  of  the  curve  where 
its  direction  is  inclined  to  the  horizon  some  entire  number  of 
degrees,  because  the  values  of  Y,  Y,  and  T are  given  for  all 
those  cases  in  the  tables.* 


1753.  It  will  be  found  sufficient  for  many  practical  purposes 
to  neglect  the  effect  of  gra'vity,  and  treat  the  motion  of  a shot 
as  if  its  path  were  a straight  line ; this  will  suffice  for  experi- 
mental pui’poses  when  it  is  desired  to  find  the  loss  of  velocity, 
or  the  time  of  flight  for  a limited  space,  the  initial  velocity 
being  high.  The  less  the  shot  is  affected  by  the  resistance  of 
tlie  air  the  more  accurate  will  be  the  results;  therefore  this 


* For  an  example  of  tliis  method,  see  Professor  Bashforth’s  Treatisa 


648 


NAVAL  ORDNANCE  AND  GUNNERY. 


method  will  apply  better  to  pointed  elongated  shot  than  to 
spherical  shot,  and  better  to  solid  shot  than  to  shell  of  the  same 
external  form. 

The  equation  of  motion  for  the  cubic  law  of  resistance  is 

d'‘s  dv  3 

= - 


dv 


or 


— — % dt. 


Suppose  that  v — V when  ^ = 0, 

1 V 


then' 


=-2i 

F e/0 


di , 


integrating  and  substituting  value  of  2d  (page  643), 


^ ~ -TVS  = I --—3 

V V w (luutt) 


or 


c’  ^ _ 500  I ^lOOOy  ^1000 


w K [\  V ) \ r y f 

which  connects  t and  v. 

d's  dv  . ds  V 

S?  = * ’ di  = di 

dv  _ vdv 
dt'~  ds' 


■C) 


whence 


and  therefore 


THE  MOTION  OF  PROJECTILES. 


64:9 


or 


o’  (1000)’  j /lOOOx 
K I V -y  y 


1000  \ 

~T^J 


.(3) 


■which  connects  s and  v. 


If  in  the  equation  i ^ = 2ls,  -we  substitute  for  — , 
^ V y ’ as  V 

■we  have 


and  integrating,  we  have 

w’hich  connects  t and  s. 
^f  we  divide 

bj 

we  obtain 


t — y-\-  hs‘ 


P 


4.U 


1 

V 

i — P = 2^5, 

V V 

1 1 _ 2 ^ 

V y'  ~ s 


•(F 


.(5) 


which  connects  v,  t,  and  s independently  of  2J,  the  coefficient  of 
resistance. 


1754.  In  determining  the  velocity  of  a shot  it  is  usual  to 
measure  the  time  in  which  a given  short  range  is  described,  and 
then,  dividing  the  space  in  feet  by  the  time  in  seconds,  the 
result  is  adopted  as  the  approximate  velocity  at  the  middle 
point.  If  the  cubic  law  of  the  resistance  of  tlie  air  be  supposed 
sufficiently  near  the  truth,  this  may  easily  be  shown  to  be 
strictly  correct  for  any  range,  so  long  as  the  path  of  the  shot 
may  be  considered  to  be  a straight  line. 

We  have  seen  that  when  V is  the  initial  velocity  and  v the 
velocity  at  the  distance  s,  then 

^ p+  2Js, 

or  if  v'  be  the  velocity  at  the  distance  then 


650 


NAVAL  ORDNANCE  AND  GUNNERY. 


Also 

time  in  seconds 


s 


by  equation  (d), 


y+  i-S 

tlie  true  velocity  at  the  middle  point  of  the  range  s. 

} 

1755.  Inasmuch  as  the  resistance  of  the  air  does  not  vary 
strictly  as  the  cube  of  the  velocity,  Avhen  formulae  (2),  (3),  and  (d) 
are  used  for  considerable  differences  of  T^and  v.  it  is  necessary 
to  use  several  numerical  values  of  K.  But  as  this  would 
be  a troublesome  operation  to  pei'form  in  each  case,  general 

tables  of  the  values  of  ^ j “ \ spherical 

and  ogival-headed  shot  [Tables  IX  and  XI],  and  also  of  the 

values  of  | for  spherical  and  elongated 

shot  [Tables  VIII  and  X],  have  been  computed.  It  is  manifest 
that  these  quantities  depend  upon  v and  V,  which  are  quite 
independent  of  the  nature  of  the  shot,  while  K is  a eoefficieut 
dependent  on  the  fonn  of  the  projectile. 


1756.  Suppose  the  initial  velocity  to  be  V,  and  that  the 
velocity  falls  from  Y to  t\,  in  space  s,,  and  in  time  t, ; from  t\  to 
-u,  in  space  s^,  and  in  time  t ; from  v„  to  v,  in  space  ^3,  and  in 
time  ...  and  from  to  v„,  in  space  and  in  time  t„. 
Let  A],  IC,  JY  ■ ■ -K„  Le  the  particular  values  of  K due  to  the 
mean  of  the  velocities  Fand  -y,,  y,  and  r,,  and  y„_,  and  r„. 
Then  we  have  from  equation  (2) 


_ 500  j /ioooy_  /loooy ) 
w * ~ A]  ( V n,  / V F / ) ’ 

^ ^ ^ ( /ioooy_  noooy  ] 

w K„  \ \ v„  J V y,  / ' ’ 

-zw  ' ~ A",  I V ^3  / \ v„  ) \ ' 


etc. 


etc., 


THE  MOTION  OF  PROJECTILES. 


651 


_ ^ j |^1000\^_  /^lOOO^ 


m “ K 


Adding  these  equations,  we  have 


W 


5002 


1 s /loooy 

U vj 


/loopy 

\ Vr,.,  J 


.(I.) 


Proceeding  in  the  same  Avay  with  equation  (3),  we  have 


(loooy  j 1000 


w 


G 

W 


a; 

(loooy 


IC 


1000 


1000  } 
1000 


■Wo 


etc. 


etc. 


therefore  — = (lOOO)"*  2 ^ 


1000  1000 


(II.) 


In  calenlating  the  nnmerical  values  of  the  right-liand  mem- 
bers of  the  above  equations,  V Avas  taken  ^'or  elongated 
shot)  = 1700  /’-s;  V,  = 1690  ; v.,  = 1680  ; = 1670,  etc.,  and 

A)  the  coefficient  corresponding  to  the  velocity  1695  J-s,  to 

1685,  to  1675,  etc.  Tables  of  the  values  of  — ^ and  — s 

were  thus  formed  corresponding  to  a loss  of  eAmry  ten  feet  in 

(f  (? 

the  velocity.  By  interpolation,  the  values  of  — and  of  — 5 

%0 

which  have  been  given  in  the  tables,  were  then  found  for  every 
foot  lost  in  velocity. 


ExxVmples  of  the  use  of  Tables  YIII,  IX,  X,  and  XI. 


1757.  (1)  Let  it  be  required  to  find  in  what  range  an  11.52- 
inch  ogival-headed  shot  Aveighing  600  lbs.  Avould  have  its  velocity 
reduced  from  1400  to  1300/‘-.s.  Let  s denote  the  required  space, 
then 


= 1865  - 1348  = 517, 


^9  = 


= 2837  ft. 


(11.52)= 

517  is  the  difference  of  the  ranges  opposite  1400  and  1300 y-s  in 
Table  YIII. 


652 


NAVAL  ORDNANCE  AND  GUNNERY. 


(2)  Let  it  be  required  to  find  in  what  time  the  velocity  of 
the  same  shot  would  be  reduced  from  1400  to  1300  f-s. 

Here  —t  — 1".258  — 0".875  = 0".383,  the  difference  of  the 
w 

times  opposite  1400  and  1300  f-s  in  Table  IX.  Hence 
t = 1L732. 


(3)  If,  on  the  other  hand,  the  initial  velocity  being  given 
1350  it  was  required  to  find  what  would  be  the  loss  of  velo- 
city in  1500  ft.,  w'e  should  have  given 


(11.50) 

600” 


- 1500  = 331.8, 


the  reduced  range.  How  opposite  the  initial  velocity  1S50  f-s 
in  Table  VIII  we  find  1599,  to  which  must  be  added  the  reduced 
range  331.8,  making  1930,8  ; and  corresponding  to  this  we  find 
the  velocity  1288.2 by  the  same  table;  hence  the  velocity  of 
an  11.52-in.  000-lb.  elongated  shot  would  fall  from  1350  to 
1 288.2 /-«  in  1500  feet. 


(4)  In  like  manner,  if  it  was  required  to  find  how  much  the 
velocity  of  the  same  shot  wonld  be  reduced  in  half  a second,  its 
initial  velocity  being  1334  f-s,  we  must  find  the  reduced  time, 

— ^ = .2212  X 0".5  = O'kllOG ; adding  this  to  1".120,  the  num- 
%o 

her  opposite  the  velocity  1334 f-s  in  Table  IX,  we  obtain  l'’.230G ; 
and  opposite  1".230G  we  obtain  by  proportional  parts  1306.6  f-s, 
which  is  the  velocity  the  shot  will  retain  at  the  end  of  half  a 
second. 

(5)  Suppose  a 15-in.  spherical  shot  weighing  452  lbs.  to  be  fired 
with  an  initial  velocity  of  1400/-S  at  a target  500  yards  off;  to 
find  the  striking  velocity.  Here  e = 14.88  in.  ; then 


w 


(14  88)^X15 
- 45200  = 


the  reduced  range ; opposite  the  velocity  1400  in  Table  X we 
find  1501,  and  adding  734.7  to  this,  we  have  2235.7,  opposite 
which,  in  the  same  table,  we  find  the  velocity  1215.8_^/-s,  which 
is  the  required  striking  velocity. 


THE  MOTION  OF  PROJECTILES. 


053 


Table  YIII  was  deduced  from  experiments  made  with  ogival- 
headed  shot  struck  with  a radius  of  diameters. 

For  high  initial  velocities  and  low  angles  of  projection,  ta- 
bles YIII  to  XI  may  be  used  to  find  approximately  the  time  of 
flight  and  trajectory  of  the  shot ; thus,  suppose  V the  initial 
velocity,  and  v the  velocity  when  the  shot  has  described  the 
space  01^'  (Fig-  369)  in  time  t,  the  effect  of  gravity  not  being 
considered;  then,  by  tables  YIII  to  XI,  it  is  possible  to  And 
OP'  and  t.  If  X,  y be  the  co-ordinates  of  P'  at  time  then 

X = OP'  cos  a \ 

y = OP'  sin  a — \gt'  j 

become  known  because  OP'  and  t are  known  approximately. 

Table  XII  will  be  useful  in  finding  the  values  of  \gf. 


The  Laav  of  Penetration  of  Projectiles.'^ 

1758.  A Commission,  appointed  by  the  French  Minister  of 
War,  carried  on  experiments  at  Metz,  in  1831  and  1835,  Avith  a 
vieAV  to  determine  the  hiAv  of  penetration  of  spherical  shot  into 
various  kinds  of  wood,  masonry,  and  earth.  Tlie  conclusions 
arrived  at  Avere,  first,  that  the  resistance  of  the  same  substance 
to  spherical  shot  of  different  diameters  Availed  as  the  square  of 
the  diameter  of  the  shot ; and,  secondly,  that  the  resistance  of 
diffrerent  substances  to  the  same  shot  varied  as  a -)-  /3  X (velo- 
city)“,  Avhere  a and  j3  Avere  constant  for  each  substance.  If,  there- 
fore, G be  the  diameter  of  the  shot  in  inches,  w its  Aveight  in 
pounds,  and  v its  velocity  in  feet  per  second,  then  the  resistance 
to  the  shot  Avill  be  expressed  by  (a  -|-  (id)  — {X  gv"),  and 

the  retarding  force  hj —d  {X gv'). 


The  following  are  the  values  of  A,  g,  and  — calculated  from 

the  values  a and  j3,  as  given  by  Didion,f  and  adapted  to  English 
measures. 


Baslifortli  On  the  Motion  of  Projectiles,  London,  1873,  p.  74. 
t Didion,  Traite,  pp.  301,  303,  and  304. 


654 


NAVAL  ORDNANCE  AND  GUNNERY. 


Substances. 

A 

Oak,  Beech,  and  Ash 

2329.4 

.004328 

734 

Elm 

1787.5 

.003322 

734 

Fir  and  Birch 

1296.0 

.002408 

734 

Poplar 

1217.7 

.002263 

734 

Sand,  mixed  with  Gravel 

486.0 

.009031 

232 

Eartli,  mixed  with  Sand  and  \ 
Gravel  ( 

670.3 

.012456 

232 

Clayey  soil 

1167.5 

.003799 

554 

Earth  from  an  old  Parapet 

782.0 

.004360 

424 

Dam])  Clay 

297.2 

.002209 

367 

Moistened  Clay 

102.4 

.000762 

367 

Masonry  of  good  quality 

6166.9 

.008595 

847 

Masonry  of  medium  quality 

4915.7 

.006851 

847 

Brickwork 

3530.4 

.004920 

847 

1759.  Suppose  that  is  the  striking  velocity  of  a spherical 
shot,  and  that  Avheii  it  has  penetrated  a distance  s,  its  veloci- 
ty is  V ; let  S denote  the  value  of  s when  the  shot  comes  to  rest, 
that  is,  when  v — 0. 


AVe  have 


(If 


vdv 

ds 


(ld_ 

w 


(A  -j-  /X  v)  ; 


or 


or 


w ^ f-,  , f 

'■  W’ 


S = 


^ wloge’“ 

-r— ^ — lo2r„ 


s= 


2ticg 

loo-  (1 

2/xcVlog,/ 


CHAPTER  XII. 


NAVAL  OPEKATIONS  ON  SHOKE.'^ 

Section  I — General  Considerations. 

1760.  Considerations. — Tlie  application  of  a naval  force  to 
tlie  purposes  of  littoral  warfare  can  only  be  considered  as  inci- 
dental to  the  general  purposes  for  Avhicli  the  navy  is  created,  and 
the  character  of  the  operations  is  necessarily  limited  by  the  char- 
acter and  strength  of  the  force.  The  squadrons  Avhich  the  navy 
might  collect  ivould  seldom  be  able  to  land  a sufficient  number 
of  men  to  cope  successfully  ivith  the  forts  or  troops  of  any  civi- 
lized nation  with  whom  ive  might  be  at  war.  When  they  have 
been  employed  by  foreign  nations  against  each  other,  or  against 
ns,  the  operations  have  been  desidtory  and  generally  attended 
Avith  deplorable  results. 

1761.  The  landing  of  seamen  would  rarely  be  resorted  to 
Avhen  opposed  by  good  infantry,  or  Avhen  the  object  to  be  attained 
Avould  take  them  very  far  from  their  base  of  operations.  It 
would  be  uuAvise,  generally  speaking,  to  expose  them  Amluntarily 
to  measure  force  in  the  held  Avith  disciplined  infantry  and  caval- 
ry. When  necessity  leads  to  such  a measure,  it  should  be  based 
on  the  unquestioned  superiority  of  the  sailors  and  marines,  both 
in  numbers  and  appointments.  Exceptional  cases  occur  Avhere 
the  strength  of  a ship  or  squadron  may  be  landed  Avith  impor- 
tant effect,  as  AA'hen  the  rights  of  the  ffag,  of  civilization,  or  of 
humanity  require  the  use  of  a naval  force  for  Avant  of  other 
means.  The  offences  of  savage  nations  or  islanders,  or  of  a pira- 
tical people,  may  be  instanced  as  cases  requh’ing  punishment  or 
intimida,tion. 

1762.  Should  it  be  judged  expedient,  hoAvever,  to  prosecute 
this  desultory  kind  of  Avarfare,  the  commanders  employed  in  it 
Avill  do  well  to  consider  that  a descent  ought  never  to  be  hazarded 


Compiled  by  Ijieutenant  J.  C.  Soley,  United  States  Navy. 


G36 


NAVAL  ORDNANCE  AND  GUNNERY. 


into  fin  enemy’s  country  vitliout  having  taken  proper  precau- 
tions to  secure  a retreat;  that  the  severest  discipline  ought  to  be 
preserved  during  all  the  operations  of  the  campaign  ; that  a 
commander  ought  never  to  disembark  but  on  a well-concerted 
plan,  nor  commence  his  military  operations  without  some  imme- 
diate point  or  object  in  vieAV  ; that  a re-embarkation  ought  never 
to  he  attempted,  except  from  a clear,  open  beach,  where  the  ap- 
proach of  an  enemy  may  be  seen  and  the  forces  covered  by  the 
fire  from  the  ships. 

1763.  The  Base. — In  all  naval  operations  on  shore,  the  first 
point  to  consider  and  fix  should  he  the  base  of  operations. 
Whenever  it  is  possible,  this  base  should  be  the  sipiadron  ; but 
Avhen  operating  in  shallow  waters,  the  largest  possible  ship  or 
ships,  whose  draught  will  admit  of  it,  should  accompany  the 
boats  and  keep  up  a constant  communication  with  the  forces  on 
shore,  so  as  to  be  ready  at  all  times  to  forward  with  dispatch 
supplies  both  of  provisions  and  ammunition,  and  to  send  for- 
ward reinforcements  if  required. 

1761.  Preparations. — Before  landing,  many  points  must  pre- 
sent themselves  for  the  consideration  of  the  commander-in-chief  : 
the  means  of  approach,  the  opportunities  for  landing,  the  nature 
of  the  ground,  the  possibility  of  maintaining  communications 
Avith  a suitable  base,  the  character  and  numbers  of  the  opposing 
force,  the  possibility  and  probability  of  accomplishing  the  ob- 
jects of  the  expedition,  and  the  safe  Avithdraival  of  the  forces. 

1765.  Taking  it  for  granted  that  all  the  preliminary  drills 
haAm  been  thoroughly  taught,  and  that  the  men  are  fully  acquain- 
ted Avith  the  manual  of  the  hoAvitzer  and  Avith  the  skirmish  drill, 
and  have  some  knoAvledge  of  battalion  drill,  the  first  consider- 
ation is  the  means  of  approach.  Every  care  should  be  taken  to 
keep  the  men  fresh  for  their  Avork  ; and  to  this  end,  the  boats 
containing  the  landing-force  should  be  tOAA’ed  to  the  place  of  dis- 
embarkation by  the  steam  launches  and  cutters  of  the  fleet. 

1766.  The  officer  in  command  of  the  landing-force  should  be 
furnished  Avith  accurate  information  of  the  depth  of  Avater  and 
the  dangers  of  naA'igation.  Care  must  be  taken  also  to  get  as 
much  knoAvledge  as  is  possible  of  the  character  of  the  ground  and 
the  opportunities  for  landing.  Generally  speaking,  an  open 
beach  Avhich  may  be  SAvept  by  the  fire  of  the  shipping  and  Avill 
offer  a firm  footing,  should  be  selected.  Judicious  means,  Iioaa-- 
ever,  must  be  used  to  get  the  force  landed  Avithont  opposition ; 
aAmiding  it  either  by  keeping  out  of  sight,  or,  if  seen,  1)a'  pulling 
rapidly  to  some  point  Avhich  may  be  more  readily  reached  bv  the 
boats  than  by  the  party  on  shore,  or  by  di\-idin'g  the  force  and 
making  false  attacks  upon  different  points. 


NAVAL  OPERATIONS  ON  SHORE. 


657 


1767.  If,  however,  such  attempts  are  unavailing,  then  it  only 
remains  to  land  promptly  in  the  face  of  the  enemy ; and  to  this 
end,  that  part  of  the  beach  must  be  selected  where  the  footing  is 
most  likely  to  be  firm,  the  bank  generally  shelving,  and  the  bot- 
tom freest  from  stones  and  mud,  least  exposed  to  tlie  surf,  and 
most  especially  where  no  cover  of  any  kind  for  the  enemy  exists 
within  some  hundreds  of  yards  from  the  shore.  It  is  also  of  the 
utmost  importance  to  keep  up  communication  with  the  base,  and 
for  this  purpose  some  vessels  should  be  stationed  to  cover  and 
protect  the  boats,  and  also  to  furnish  assistance  to  the  party  on 
shore  in  whatever  way  it  may  be  needed. 


Section  II — Landing. 

1768.  Details. — Before  landing,  the  station  of  each  boat 
should  be  fixed,  and  every  officer  should  be  made  acquainted  with 
ttie  details  of  the  organization,  and  particularly  with  his  position 
after  landing. 

The  small-arm  men  should  be  formed  into  companies  of  forty 
men,  with  four  petty  officers,  and  armed  Avith  breech-load- 
ing rifles  and  bayonets  ; each  company  to  be  commanded  by 
a lieutenant  and  two  other  officers.  The  howitzer  crews  should 
be  composed  of  twenty-one  men,  each  man  being  armed  with  a 
cutlass  and  breech-loading  pistol. 

1769.  Each  sliip  landing  two  companies  should  also  furnish 
twelve  pioneers  : four  with  a saw  and  axe  each,  four  with  a pick- 
axe and  spade  each,  four  with  small  crowbars  and  sledge-ham- 
mers each,  or  such  intrenching  or  other  tools  as  the  nature  of 
the  expedition  may  require  ; the  men  should  be  equipped  ivith 
those  tools  to  whose  use  they  are  most  accustomed : carpenters 
with  saws  and  axes,  firemen  with  intrenching-tools.  Vessels 
fumishing  a smaller  contingent  of  infantry  should  furnish  a pro- 
portionate number  of  pioneers.  An  armorer,  avIio  ivill  join  the 
pioneers,  should  be  sent  with  each  landing  party,  and  furnished 
with  cleaning-rods,  screiv-drivers,  and  gimlets.  The  ship’s 
bugler  and  the  drummer  and  lifer  should  be  sent  with  the  men. 

1770.  Every  man  in  the  command  should  liave  a canteen  and 
haversack,  and  a blanket,  folded  and  slung  over  his  shoulder. 

1771.  Each  division  of  boats  should  carry  a distinguishino- 
flag;  scaling-ladders,  intrenching-tools,  and  other  implements 
should  be  cariied  by  designated  boats. 

1772.  If  landing  in  a heavy  surf,  the  ammunition  should 
be  put  into  small  powder-tanks  ivitli  the  lids  ivell  screived  doivn. 


658 


NAVAL  ORDNANCE  AND  GUNNERY. 


and  the  howitzers  might  be  rafted  on  shore  if  they  could  not  be 
carried  safely  in  the  boats. 


Fig.  370. 


1773.  Landing. — Should  the  distance  to  the  point  of  landing 
be  considerable,  the  boats  should  be  towed  to  within  a suitable 
distance  of  the  beach,  being  careful  to  keep  out  of  range.  On  ar- 
riving opposite  the  place  of  disembarkation,  the  tow-ropes  should 
be  cast  off  and  the  line  fonned  preparatory  to  landing.  The 
boats  containing  the  heavy  howitzers  should  be  on  the  extreme 
flanks,  next  the  light  howitzers  which  are  to  be  landed,  and  the 
main  body  of  infantry  in  the  middle,  with  the  skirmishers  in  the 
centre.  There  should  be  a reserve  force  of  howitzers  and  infan- 
try ready  to  be  dii’ected  to  either  flank,  or  to  reinforce  any  par- 
ticular part  of  the  line.  The  howitzer  divisions  should  be  form- 
ed in  echelon,  so  as  to  deliver  a cross-fire  on  that  part  of  the 
beach  where  the  landing  is  to  be  made.  IVlien  all  these  disposi- 
tions have  been  made,  the  boats  should  pull  in  for  the  landing- 
place. 

177L  It  should  be  borne  in  mind  that  the  force  will  be  at  the 
greatest  disadvantage  when  disembarking  in  the  face  of  a strong 
opposition  ; for  in  using  all  the  celerity  that  is  practicable  with 


NAVAL  OPERATIONS  ON  SHORE, 


059 


trained  men,  there  must  be  a few  minutes  when  the  pieces  to  be 
put  ashore  must  be  inactive.  Therefore  it  is  necessary  that,  as 
soon  as  the  howitzer  fii-e  has  cleared  the  beach,  a strona;  body  of 
skirmishers  and  infantry  should  be  landed,  to  engage  the  enemy 
during  the  disembarkation  of  the  howitzers.  ISTo  gun  should  be 
landed  before  there  are  at  least  forty  men  on  the  beach. 

1775.  Meanwhile  the  fire  of  the  heavy  howitzers  should  be 
discontinued,  unless  they  can  safely  fire  shell  over  the  heads  of 
the  party  on  shore.  The  skirmishers  should  immediately  advance 
and  seize  the  nearest  cover,  while  the  main  body  of  infantry  will 
pull  in  and  land,  followed  by  the  howitzers.  Immediately  the 
main  body  of  infantry  has  landed  they  should  be  deployed  into 
line  of  battle,  with  a strong  skirmish  line  in  advance,  and  they 
should  take  up  the  strongest  position  possible,  the  howitzers  be- 
ing brought  into  position  as  fast  as  they  are  landed.  The  line 
should  be  formed  in  such  a manner  that  the  flanks  will  if  pos- 
sible be  protected  by  the  nature  of  the  ground,  or  by  the  fire 
from  the  ships. 

1776.  The  Boats  will  always  land  a boat’s  length  apart.  Be- 
fore leaving  the  ship,  four  boat-keepers  should  be  appointed  to 
each  boat  caiTying  a howitzer,  and  two  for  the  others,  with  an 
officer  in  charge  of  each  division  of  boats,  who  should  on  no 
account  leave  them.  The  boats  should  be  hauled  off  to  their 
anchors  with  a long  scope  of  cable,  and  a man  left  in  each  boat  to 
veer  in,  that  the  troops  may  be  readily  embarked.  The  officer 
left  in  charge  of  the  boats  should  be  careful  to  avoid  being  sur- 
prised, and,  if  circumstances  will  admit,  should  strengthen  his 
position  by  cutting  down  trees  and  throwing  up  small  breast- 
works a short  distance  in  front.  There  should  be  at  least  one 
boat  with  a full  crew  left  with  him,  to  enable  him  to  keep  up 
communication  with  his  base ; he  should  also  endeavor  to  keep 
up  communication  with  the  commander  of  the  forces  by  means 
of  signal-men. 

Section  III. — On  the  March. 

1777.  The  Advance. — If  the  force  has  landed  without  oppo- 
sition, the  first  duty  wdll  be  to  make  a reconnaissance,  in  order  to 
ascertain  the  position  of  the  enemy,  the  situation  of  the  nearest 
towns  and  villages,  the  direction  of  roads,  streams,  etc.,  and  to 
obtain  a general  idea  of  the  country.  If  it  becomes  necessary  to 
advance  into  the  country,  the  manner  of  advance  must  be  deter- 
mined by  the  commanding  officer.  If  the  country  be  open,  or 
if  no  opposition  be  met  with,  the  column  may  take  up  the  march 
in  close  order. 


660 


NAVAL  ORDNANCE  AND  GUNNERY. 


1778.  Advance-guards. — If,  on  the  other  hand,  the  line  of 
march  should  pass  over  hilly  country,  or  through  woods,  or  if 
there  are  any  indications  of  the  presence  of  an  enemy,  every 
precaution  should  he  taken  against  a sui’prise,  by  throwing  out 
advance-guards,  rear-guards,  and  flankers,  as  may  be  deemed 
necessary. 

1779.  The  object  of  these  guards  is  to  give  time  for  the  col- 
umn to  make  the  necessary  preparations  for  attack  or  retreat  in 
case  the  enemy  are  discovered. 

1780.  The  guards  should  each  consist  of  at  least  one  ofiicer. 


Rear  k Guard, 


0 Qfe,  Offizcr 


Aovance  a Guard. 


OpFiQta  Par  Off,  o 


Fig.  371. 


one  petty  oflicer,  and  twenty  men,  arranged  as  in  the  figure. 
Generally  speaking,  the  advance-guard  should  be  from  one-fifth 
to  one-tenth  of  the  whole  force,  and  should  be  accompanied  by  a 
detachment  of  signal-men  and  pioneers.  The  advance-guard 
may  be  increased  or  diminished  at  the  discretion  of  the  com- 
manding oflicer. 

1781.  When  tlie  column  halts,  the  advance-guard  does  the 
same,  but  the  men  at  the  head  should  occupy  the  neighboring 
heights,  if  there  be  any  within  four  or  five  hundred  yards. 
There  should  never  be  less  than  three  men  at  the  head,  and  dif- 
ferent divisions  shoidd  endeavor  to  keep  their  distance  from  the 
others.  On  coming  to  a wood,  the  men  at  the  head  should  be 
reinforced,  and  some  sent  through,  and  others  around  it,  the 
column  halting  until  the  wood  has  been  patrolled.  The  same 
rule  should  be  followed  on  coming  to  a Gllage.  They  should 
never  enter  a defile  without  previously  occupying  the  heights  on 
either  side  by  flanking-parties.  At  night  the  distances  should  be 
reduced,  and  communication  kept  up  with  a chain  of  men  just 
far  enough  apart  to  see  each  other.  Should  the  advance-guard 
be  attacked,  it  should  engage  with  spirit,  and  never  fall  back 
until  absolutely  obliged  to  do  so,  and  then  the  retreat  should 


NAVAL  OPERATIONS  ON  SHORE. 


661 


be  made  on  either  side  of  the  column,  and  never  on  the  column 
itself. 

1782.  Rear-gtjakds. — The  object  of  rear-guards  is  to  prevent 
the  enemy  from  approaching  the  column  unperceived,  and  the 
men  composing  it  should  be  picked  men.  Should  they  be  at- 
tacked, the  men  in  rear  should  be  reinforced  by  the  other  squads, 
aud  the  enemy  must  be  held  in  check.  If  they  retire,  the  same 
rules  apply  to  them  as  to  the  advance-guard.  Whenever  the 


-X- -X  — 

Com.  Off. 

X ! 

AIDES.  XXX 


Field  Officers. 


X 

X 

Company  Officers. 

X X 

X 

X 

X 

XX  X 

X 

X X 

X 

XX 

XX 

X X X X 

X X 

XX 

X 

XX 

XX 

XXX  X 

X X 

X 

X 

X 

X 

X 

X 

5 >«  X 

J>'X  X 

^XXx 
X X 


v. 


□ ^ 

D -^H 


Q-5. 
0 

Cooking  Places. 


D-^ 


Sinks. 


Fig.  372. 

Bivouac  of  a force  of 

1 Comp.  Pioneers. . ..70  '| 

10  Howitzers 220  i 

12  Companies 1008  f 

Officers 54  J 


1352  men. 


602 


NAVAL  ORDNANCE  AND  GUNNERY. 


column  halts,  the  rear-guard  should  face  to  the  rear.  Flankers 
are  placed  as  in  the  hgure,  on  either  or  both  flanks,  as  may  be 
necessary,  and  their  movements  are  governed  by  the  same  gen- 
eral rules  as  the  other  guards ; all  parties  so  thrown  out  should 
keep  themselves  concealed  as  much  as  possible. 

1783.  Bivouac. — In  selecting  a site  for  a bivouac,  wood  and 
water  are  the  great  requisites.  In  cold  weather,  woods  are  the 
warmest  places,  but  in  tropical  climates  it  is  better  to  bivouac  in 
the  open.  Dry  and  sheltered  positions  should  be  chosen.  If 
obliged  to  bivouac  where  one  may  have  to  engage,  it  is  better  to 
take  a position  in  advance  of  the  one  which  must  be  occupied  in 
fighting.  If  obliged  to  bivouac  near  a marsh,  there  should  be  some 
rising  ground  between  it  and  the  position  selected ; this  should 
be  done  if  possible  some  time  before  the  arrival  of  the  column. 

1781.  On  arriving  on  th^  ground  selected,  the  infantry  and 
howitzers  should  wheel  into  open  column  by  divisions,  crews  of 
howitzers  formed  to  the  rear  and  the  men  mustered,  absentees 
reported  to  the  commanding  officer,  and  arms  stacked.  The  men 
should  sleep  where  they  stand  in  ranks,  officers  sleeping  opposite 
the  flanks.  Cooking  places  should  be  made  on  the  other  flanks, 
and  sinks  dug  some  two  hundred  yards  off.  The  camp-guard 
should  be  immediafely  posted,  whose  duty  it  is  to  prevent  all 
persons  from  leaving,  except  officers  and  authorized  persons. 
The  advance-guard  and  rear-guard  should  be  relieved  in  the 
afternoon,  at  tlie  time  of  going  into  bivouac. 

1785.  Grand-guaed. — Besides  the  regular  camp-guard,  which 
is  charged  with  maintaining  order  and  discipline  in  the  camp, 
there  should  be  a grand-guard  thrown  out  in  the  dh’ection  of  the 

Sentinels. 


aqpoaapqp  ppppn^tnpnnpappcipap 

''J  jk  '1-'  Out':.:  Posts ''J  V M'  jF 

cncpcp  cpcpiziicincfaa 


PlCH.eTS. 


t:  n 


Grand-Guard. 
Fig.  373. 


NAVAL  OPERATIONS  ON  SHORE, 


663 


enemy.  This  should  consist  of  one  or  two  companies,  aecord- 
ino-  to  the  nature  oi  the  service  and  the  ground  to  be  covered. 
The  first  line  is  the  grand-guard,  one-haii  of  whom  may  rest 
six  hours,  and  the  otner  half  be  awake  and  ready  for  duty 
six  hours.  This  is  the  post  from  which  the  pickets,  outposts, 
and  sentinels  radiate.  The  picket-guards  compose  the  second 
line,  and  are  relieved  from  the  grand-guard  every  eight  hours ; 
one-half  to  be  under  arms  half  the  time,  the  other  half  to  rest 
half  the  time.  The  third  line  are  the  outposts,  consisting  of 
nine  men,  relieved  from  the  pickets  every  two  hours  : these  men 
should  be  always  watchful.  The  fourth  or  front  line  of  senti- 
nels are  to  be  relieved  from  the  outposts  every  hour : they 
patrol  constantly,  and  connect  with  one  another. 

1786.  The  ofiicer  commanding  the  grand-guard  should  be  sta- 
tioned at  the  first  line,  visiting  the  second  every  six  hours,  and 
generally  supervising.  The  other  officers  should  be  stationed 
with  the  pickets,  and  should  visit  the  outposts  and  sentinels  fre- 
quently. The  petty  officers  command  the  outposts.  It  is  not 
necessxry  that  the  line  should  be  straight,  but  the  general  princi- 
ples should  always  be  canned  out.  it  is  generally  advisable  to 
have  some  howitzers  with  the  grand-guard,  on  the  first  line, 
posted  so  as  to  command  the  approaches. 

1787.  When  attacked,  the  outposts  forming  as  skirmishers 
move  to  the  support  of  the  sentinels ; pickets  may  move  forward 
to  support  the  others,  or  all  may  retii'e  skirmishing  as  the  nature 
of  the  attack  may  suggest.  Should  the  attack  be  so  strong  that 
the  whole  grand-guard  is  compelled  to  retire,  then  each  line  will 
retire  fighting.  When  an  attack  commences,  a message  should 
be  instantly  sent  to  the  commanding  officer,  detailing  i s nature 
and  giving  any  necessary  information. 

Section  1 V. — Engaging. 

1788.  The  Attack. — Thisj^peration  must  be  considered  un- 
der two  phases : 1st.  The  column  has  halted  within  sufficiently 
easy  distance  of  the  enemy  to  make  a march  of  from  five  to  ten 
miles,  with  the  intention  of  attacking  as  soon  as  it  arrives.  2d.  It 
has  halted  at  too  great  a distance  for  that  purpose,  so  it  marches 
up  to  him,  and  bivouacs  for  the  night  to  attack  next  morning. 

1789.  If  the  column  has  been  closely  pursuing  the  enemy, 
with  the  advance-guard  continually  in  contact  with  the  enemy’s 
rear,  it  may  happen  that  the  retreating  force  m xy  be  suddenly 
found  drawn  up  to  receive  battle.  Under  su:‘h  circumstances,  it 
would  be  better  to  act  as  in  the  second  case,  particularly  if  it  oc- 
curs late  in  the  day,  in  which  case  all  preparations  for  attack 


661 


NAVAL  ORDNANCE  AND  GUNNERY. 


should  be  made  late  in  the  night ; hut  should  the  enemy  be  de- 
moralized from  previous  defeats  or  other  causes,  he  should  be 
attacked  when  he  turns  to  show  fight,  as  in  the  first  case. 

1790.  In  either  case,  the  nature  of  the  country  and  its  com- 
munications must  determine  the  mode  of  the  advance ; but  it 
should  resemble  closely  the  order  in  which  it  is  intended  to  fight, 
covered  by  swarms  of  skirmishers  as  an  advance-guard.  If  it  is 
impossible  to  advance  in  line  of  battle,  the  double  column  is  sug- 
gested as  being  the  easiest  to  deploy.  In  any  case,  the  column 
should  be  kept  closed  up  and  ready  to  he  deployed  into  line, 
followed  in  the  rear  by  the  reserve. 

Skirmish  Line — 3 Companies. 


12 


a 


SI 


10 

Q 


Line 

l~  ^ I \-  ^ \ ^ \ l|l 


22P  Line 


f 


7 


Reserve 


Fig.  374. — FoncE  deployed,  re.\dy  to  attack. 

Arrived  within  the  fire  of  the  enemy’s  guns,  the  position 
should  be  reconnoitred,  and  the  column  deployed  into  line  and 
placed  in  position. 

1791.  These  aiTangemcnts  should  be  made  under  cover  of  the 
advanced  line  of  skirmishers.  Having  decided  on  what  part  of 
the  enemy’s  line  to  make  his  false  and  real  attacks,  the  command- 
ing officer  should  attack  as  soon  as  possible,  if  the  chances  are  in 
his  favor  : delays  in  such  cases  are  very  dangerous.  The  artil- 
lery should  he  massed  opposite  that  part  of  the  enemy’s  line 
where  the  real  attack  is  to  he  made.  It  is  sometimes  necessary 
to  begin  an  action  with  all  the  guns  available  at  the  moment,  in 
order" to  keep  the  enemy  at  a distance  while  the  troops  are  get- 
ting into  position. 


NAVAL  OPERATIONS  ON  SHORE. 


665 


1792.  The  commanding  officer  must  decide  whether  the  as- 
sault is  to  be  made  in  line  or  in  column.  If  in  line,  it  must  be 
remembered  that  the  charge  must  occasion  much  disorder  in  the 
line,  which,  unless  supported  on  the  instant  of  its  first  success, 
is  sure  to  be  driven  hack  by  a counter-charge.  For  this  reason, 
a second  line  should  be  formed  and  placed  so  as  to  cover  the 
assault. 

1793.  Taking  it  for  granted  that  it  was  decided  to  attack  the 
enemy’s  left,  the  disposition  would  be  as  in  the  figure.  Of 


Fm.  375. — Force  attacking  Enemy’s  Left  Flank. 

course,  before  the  advance,  all  the  available  guns  should  be 
brought  to  bear  on  the  left.  When  it  was  considered  that  the 
artillery  fire  had  told  sufficiently,  the  attacking-party  should  ad- 
vance. As  soon  as  they  become  engaged  a partial  advance  of 
the  whole  line  should  take  place.  The  advance  should  be  closely 
covered  by  skh’raishers,  who  should  push  on  as  near  to  the  ener 
my’s  lines  as  possible. 

1794.  If,  however,  during  the  march  the  enemy  should  be 
unexpectedly  found  in  position,  or  when  called  upon  to  act  as 
in  the  first  case,  more  time  will  be  required  to  deploy  and  to 
make  arrangements  for  attacking.  The  advance-guard  should 
take  up  some  defensive  position,  and  strengthen  it  if  possible. 
The  commander  should  hasten  to  the  front  and  reconnoitre  the 


606 


NAVAL  ORDNANCE  AND  GUNNERY. 


ground.  Having  done  so,  orders  must  be  sent  to  the  command- 
ers of  the  several  divisions,  telling  them  where  to  deplbv,  etc. 
These  dispositions  must  depend  entirely  on  whether  it  is  intend- 
ed to  await  the  enemy’s  attack  or  to  attack  first,  and  in  the  latter 
case,  on  what  part  of  the  enemy’s  line  the  attack  is  to  be  made. 

1795.  The  Skirmishers. — Specially  instructed  men  are  ne- 
cessary for  this  work.  In  covering  a line  or  a column  advanc- 
ing to  attack  an  enemy,  their  numbers  should  be  increased 
according  as  the  nature  of  the  ground  to  be  moved  over 
affords  cover ; every  skirmisher  of  the  enemy  should  be  wiped 
out  by  them  from  the  front  of  the  attacking-liue,  and  a con- 
tinued fire  maintained  up  to  the  last  moment,  as  this  will  serve 
to  screen  the  advance  and  to  steady  the  men.  They  should 
move  forward  quickly  as  soon  as  the  advance  commences,  keep- 
ing about  150  yards  ahead,  and  under  cover  as  much  as  they 
can,  and  press  as  close  to  the  enemy’s  line  as  possible,  even  up 
to  150  yards.  Too  much  care  cannot  be  taken  in  guarding 
against  a waste  of  ammunition  ; the  firing  should  be  deliberate 
and  careful  in  the  extreme,  and  not  a shot  thrown  away.  Ean- 
doni  filing  only  encourages  and  gives  confidence  to  the  enemy, 
vdiile  it  depletes  one’s  own  resources. 

1796.  The  Infantry. — In  advancing  the  main  body  of  the 
infantry  to  the  attack,  they  should  be  distributed  in  two  lines, 
as  above  shown  (Fig.  375).  The  lines  should  advance  together  at 
a steady  quick  march  to  within  150  yards  of  the  enemy,  when 
the  order  will  be  given  to  the  first  line,  “ Prepare  to  charge.” 
If  the  skirmishers  have  pushed  up  close  to  the  enemy,  they  will 
lie  down,  and  the  first  line  passing  over  them  Avill  commence 
their  charge  as  they  do  so.  The  second  line  should  continue  the 
movement  in  qnick-step.  At  the  order  ‘‘Charge,”  let  the  men 
cheer  with  a will,  and  take  up  the  run  with  their  pieces  at  a trail, 
seizing  them  with  the  left  hand  as  they  close  with  the  enemy. 

1797.  The  Artillery. — The  ground  in  the  vicinity  of  the 
point  to  be  attacked  must  be  swept  by  a heavy  cannonade  be- 
fore the  attacking-force  is  launched  forward.  The  heaviest  pos- 
sible fire  should  be  maintained  up  to  the  last  moment,  and  when 
the  attacking-force  has  advanced  into  such  a position  as  to 
impede  the  nre,  the  howitzers  should,  if  possible,  be  advanced 
into  such  a position  that  they  can  reopen. 

1798.  After  the  charge  commences,  they  should  devote 
themselves  to  the  other  part  of  the  line,  or  be  placed  in  such  a 
position  as  best  to  repel  a counter-charge,  or  they  may  be  used 
as  circumstances  dictate,  being  careful  to  keep  some  companies 
with  them.  The  skirmishers,  after  the  charge  has  commenced, 
should  form  on  the  artillery 


NATAL  OPERATIONS  ON  SHORE. 


667 


1799.  The  guns  should  always  be  massed  Avhen  it  is  possible, 
as  the  moral  eliect  is  much  greater  than  when  they  are  scat- 
tered, and  their  lire  should  he  directed  to  the  enemy’s  men 
rather  than  to  Ins  guns.  They  should  always  be  supported  by 
infantry  on  one  or  both  flanks,  but  never  in  rear. 

1800.  The  Defence. — Great  care  is  necessary  in  the  selection 
of  a position  where  a defence  is  to  be  made.  It  shoidd  afford  a 
depth  of  live  or  six  hundred  yards  on  which  to  manoeuvre,  with 
free  communication  from  right  to  left,  and  with  roads  in  rear 
by  which  to  retreat.  The  protection  of  the  flanks  is  a serious 
consideration  ; one  at  least  ought  to  rest  on  some  impassable 
obstacle.  Tlie  general  line  of  positions  must  either  curve  con- 
vexly  or  concavely  towards  the  enemy,  or  there  must  be  a mix- 
ture of  both.  If  the  flanks  are  strong  and  not  easily  ap- 
proached or  turnecl,  the  concave  is  the  stronger.  If,  on  the 
contrary,  the  spots  where  the  flanks  rest  present  no  feature  of 
strength,  it  is  better  to  have  them  retired,  thus  forming  a con- 
vex front  to  the  enemy. 

1801.  An  obstacle,  not  actually  an  impassable  one,  running 
somewhat  parallel  to  the  general  line  of  the  position  and  about 
two  or  three  hundred  yards  in  front  of  it,  adds  greatly  to  its 
strength  ; but  such  obstacles  as  high  banks,  hedges,  etc.,  which 
would  afford  any  cover,  are  most  dangerous.  Obstacles  that 
cut  up  one’s  own  lines  are  to  be  avoided,  and  also  positions  with 
wooded  ground  in  front  of  them.  If  there  is  but  one  road  to 
retreat  by,  it  should  run  from  near  the  centre. 

1802.  The  Infantry. — In  distributing  the  troops  along  a 
chosen  position,  some  parts  of  it  will  require  to  be  held  by  a 
much  greater  number  than  others,  and  the  commander  must 
decide  which  is  the  impoi’tant  point  or  key,  and  that  point 
should  be  occupied  in  force,  with  the  reserves  near  at  hand. 
He  should  then  set  to  work  to  strengthen  himself  artificially. 
The  formation  of  the  command  into  two  lines  instead  of  one 
has  many  advantages,  as  it  keeps  it  more  compact  and  renders 
it  easier  to  support  any  particular  point  of  the  line ; but  the 
second  line  should  be  used  very  sparingly,  and  only  when  the 
necessity  is  urgent. 

1803.  The  front  of  the  infantry  will  always  be  covered  by 
skirmishers,  so  that  no  fire  can  be  delivered  till  they' have  been 
driven  in : when  the  front  has  been  cleared  and  the  enemy  is 
advancing,  it  is  time  for  the  infantry  to  open  fire,  kneeling  and 
with  volleys,  hy  word  of  command.  File-firing  should  not  be 
used  at  such  a time,  as  it  is  so  difficult  to  stop  it.  It  will  be  for 
the  commander  to  decide  when  it  shall  stop,  and  then  the  order 
should  be  given,  “ Prepare  to  charge,”  and  let  them  go  in  with 


668 


NAVAL  ORDNANCE  AND  GUNNERY, 


a cheer.  An  advancing  enemy  shonlcl  never  be  awaited  in  tlie 
open  plain  : in  all  such  attacks  there  is  a moment  when  the 
defendant  must  charge.  Immediately  after  charging  the  men 
should  be  reformed  and  led  back  to  their  original  position  with- 
out being  allowed  to  go  too  far  in  their  broken  state. 

1804.  The  Artillery. — In  defence,  as  in  attack,  it  is  the 
duty  of  the  artillery  to  devote  itself  to  the  enemy's  men,  and  it 
should  be  placed  on  that  flank  which  occupies  the  strongest  posi- 
tion. When  neither  flank  has  any  natural  supports,  the  guns 
should  be  massed  in  the  centre.  These  rules  can  be  adhered  to 
when  the  front  does  not  exceed  1200  yards ; beyond  that,  bat- 
teries must  occupy  several  parts  of  the  position. 

180.5.  Squares  to  resist  cavalry  should  only  be  formed  when 
absolutely  necessary,  as  the  square  is  a mark  for  every  descrip- 
tion of  tire.  In  forming  them,  advantage  should  be  taken  of 
any  favorable  ground.  If  there  is  an  obstacle,  such  as  a small 
hedge,  ditch,  or  fence,  it  is  better  to  form  at  about  twenty  yards 
from  it  than  to  hug  it  closely. 


Section  V. — Held  Fortification. 

1806.  Definitions. — When  an  armed  force  is  constrained  to 

act  on  the  defensive,  from  disparity  of  numbers  or  strength,  it 
should  endeavor  to  counterbalance  this  disparity  by  selecting  a 
position  on  which  to  receive  battle  Avhich  will  atford  everv 
military  advantage  to  itself  and  prove,  in  a corresponding 
degree,  unfavorable  to  the  assailant  Such  a position  should 
present  natural  obstructions  to  the  advance  of  an  assailant ; it 
should  screen  the  assailed  from  tire ; it  should  command  the 
ground  over  which  the  assailant  must  advance  ; it  should  com- 
mand the  lines  of  approach  by  a front  and  cross  tire  ; it  should 
offer  no  obstructions  to  the  free  movements  of  the  assailed ; it 
should  have  natural  points  of  support  both  on  the  flanks  and  in 
the  rear ; and  its  lines  of  retreat  should  be  ample  and  secure. 
As  natural  defensive  positions  may  rarely  possess  the  most  essen- 
tial of  these  advantages,  their  defects  must  be  remedied  by 
artiticial  means.  These  means  are  fortifications. 

1807.  Fortification  may  therefore  be  detined  as  the  art  of  so 
arranging  a position  selected  for  defence  that  an  inferior  force 
shall  be  able  to  resist  with  advantage  the  assaults  of  one  supe- 
rior to  it. 

The  covering  mass  is  termed  a Parapet  when  it  shelters  tlie 
assailed  from  the  view  and  tire  of  the  assailant,  and  affords  a 
sweeping  fire  over  the  lines  of  approach. 


NAVAL  OPERATIONS  ON  SHORE. 


669 


1808.  The  Profile  is  the  vertical  section  showing  the  thick- 
ness and  height  of  the  parapet  and  the  slopes  in  front  and  rear. 


ABMN,  Ground  line.  EF,  Superior  Slope.  JK,  Counterscarp. 

BO,  Banquette  Slope.  FO,  Exterior  Slope.  HIJK,  Ditch. 

CB,  Banquette.  OH,  Berm.  LM,  Glacis. 

BE,  Interior  Slope.  HI,  Scarp. 

The  most  nsnal  obstruction  to  impede  the  enemy’s  approach 
is  the  Ditch,,  which  is  placed  in  front  of  the  parapet,  for  which 
it  furnishes  the  material. 

Any  little  ditch  made  behind  a breastwork  for  the  men  to 
stand  in  for  cover  is  called  a Trench.  The  excavation  of  this 
also  furnishes  material  for  the  parapet. 

1809.  A Banquette  is  a step  on  which  men  stand  to  fire  over 
the  parapet.  It  should  generally  be  about  4-  feet  6 inches  below 
the  top. 

1810.  A Bermi?,  a narrow  strip  left  between  the  parapet  and 
the  ditch  to  prevent  the  earth  from  falling  into  the  ditch. 

1811.  The  top  of  the  parapet  is  termed  the  Superior  Slope; 
the  interior  face,  when  arranged  for  infantry,  is  termed  the 
Interior  Slope  ; when  for  artillery,  the  Ge7iouilleTe  ; theextej’ior 
face  is  the  Exterior  Slope. 

1812.  The  side  of  the  ditch  adjacent  to  the  parapet  is  called 
the  Scarp  ; the  side  opposite,  the  Counterscarp. 

1813.  A mound  of  earth  placed  in  front  of  the  counterscarp, 
with  a gentle  slope  outwards,  is  called  a Glacis. 

1811.  All  Abattis  is  an  obstacle  formed  by  felling  trees  and 
laying  them  side  by  side,  with  the  branches  pointed  and  turned 
towards  the  enemy. 

1815.  A Traverse  is  any  mass  Avhich  is  intei-posed  to  protect 
the  men  from  fire  which  comes  in  any  direction  except  the 
front. 

1816.  A Revetment  consists  of  a facing  of  stone,  wood,  or 
sods,  or  any  other  material  to  sustain  an  embankment  when  it 
receives  a slope  steeper  than  is  natural.  They  are  used  only  for 
the  interior  slope  of  the  parapet,  and  for  the  scarp. 

1817.  Relief  the  height  of  the  crest  of  the  parapet  above 
the  bottom  of  the  ditch. 


670, 


NAVAL  ORDNANCE  AND  GUNNERY. 


1818.  Command  is  its  height  above  the  level  of  the  surround- 
ing country. 

1819.  In  order  to  establish  mutual  defensive  relations  between 

all  the  parts,  certain  parts  may  be  thrown  forward  towards  the 
enemy,  and  tliey  are  denominated  advanced  parts  j other  yjor- 
tions,  denominated  are  withdrawn  from  the  enemy 

and  protected  from  their  fire  by  the  advanced  parts. 


and  TJ  VW,  Advanced  Parts.  QT,  jSF".  Lines  of  Defence. 
liSTU,  Retired  Parts.  PQR.UVW,  Salient  An<rles. 

PQ,  QR,  UV,  VW,  Faces.  RST,  STU,  Re-entering  Angles. 

RS,  TV,  Flanks.  VA,  QB,  Capitals. 

S2’,  Curtain. 

1820.  This  arrangement  naturally  indicates  that  the  general 
outline  of  the  plan  must  present  an  angular  system — some  of 
the  angular  points,  denominated  saUoits,  being  towards  the 
enemy,  and  otliers,  called  re-enterings,,  being  towards  the  assailed. 
When  such  a disposition  is  made  it  is  termed  a flank  'disposi- 
tion, because  the  enemy’s  flank  is  attained  by  the  fire  of  the 
retired  parts  when  he  is  advancing  upon  the  salients.  No  salient 


Fig.  377. — Indented  Line. 


NAVAL  OPERATIONS  ON  SHORE. 


671 


should  be  less  than  60°.  A line  of  defence  should  not  exceed 
300  yards. 

1821.  Plans. — The  simplest  line  that  can  he  used,  where  the 
front  to  be  defended  is  of  limited  extent  and  the  flanks  and 
rear  are  secure,  is  a rkjlit  line.  But  from  this  line  only  a 
direct  fire  can  be  obtained  ; and  for  extended  forms  a combina- 
tion of  front  and  flank  fire  may  be  obtained  by  using  the  in- 
dented line.  (Fig.  377.) 

1822.  The  plan  of  works  for 
positions  which  have  the  rear  se- 
cure, but  are  assailable  in  the 
front  and  on  the  flanks,  admits 
of  great  variety.  The  simplest 
is  a work  of  two  faces  only,  the 
salient  being  towards  the  ene- 
my’s line  of  approach.  This  is 
termed  a Bedan  (Fig.  378).  Its 
faces  should  receive  such  a direc- 
tion as  to  sweep  the  approaches 
to  the  flanks  ; from  the  angular 
point,  however,  only  a single  line 
of  direct  tire  can  be  brought  to  bear  on  the  section  in  ad 

vance  of  it ; to  remedy  this  a 
portion  of  the  salient  is  filled 
in  so  as  to  form  a short  defen- 
sive line,  ]ierpendicular  to  the 
capital.  This  is  termed  a Pan- 
coxopee. 

1823.  When  the  faces  of  the 

redan  cannot  be  placed  so  as  to 

„ „ „ „ sweep  the  flank 

Fig.  379. — Plan  of  the  Priest-cap.  vi  i • 

without  making 

angle  too  acute,  the  plan  may  be  what  is  termed  a Priest- 
cap  or  Swallow-tail  (Fig.  379), 
in  which  the  two  main  faces 
sweep  the  flank  approaches,  and 
instead  of  the  pan-coupee,  a 
broken  line  forming  a re-enter- 
ing angle  is  placed  in  the  salient, 
and  aflords  a cross-fire  on  the 
ground  in  front. 

1821r.  When  the  flank  ap- 
proaches extend  to  the  rear,  a 
flank  (Fig.  380)  is  added  to  each 
face  of  the  redan,  and  receives  Fig.  380. — Plan  op  the  Lunette. 
such  a direction  as  to  sweep  that  bG,  CD,  Faces.  AB,  BE,  Flanks. 


approaches 
the  salient 


E 


Fig.  378. — Plan  of  the  Redan. 
AB,  CD,  Faces.  AD,  Gorge. 
BG,  Pan-coupee. 


T 


672 


NAVAL  ORDNANCE  AND  GUNNERY. 


portiou  of  tlie  flank  approach,  which  cannot  he  reached  hy  the 
faces  except  by  a very  oblique  fire.  This  is  tenned  a Lunette. 

1826.  Such  works  as  are  assailable  on  all 
sides  must  present  an  unbroken  line  to  the 
assault,  and  are  termed  enclosed  worhs. 
They  are  generally  of  three  classes : re- 
doubts, star  forts,  and  bastioned  forts. 

1826.  A liedouht  may  be  a polygonal  fig- 
ure of  any  number  of  sides  (Fig.  381).  That 
most  usually  taken  is  the  square. 

1827.  A Star 
consists  of  a 

polygon  having 
alternate  salients 
and  re-enterings 


(Fig.  382).  It  is 


Fig.  381. 

Plan  of  a Square  Re- 
doubt, witli  one  angle 
indented  and  the  other 
arranged  with  a pan- 
coupee. 

generally  planned  by  placing  redans 
on  the  middle  of  the  faces  of  a square 
redoubt.  The  star  fort  is  but  little,  if 
at  all,  superior  to  the  square  redoubt, 
as  its  flanking  dispositions  are  imper- 
fect, and  it  presents  a much  longer 
line  to  be  defended.  It  would  only 
be  useful  on  broken  ground  or  irregu- 


Fig.  383. 

Plan  of  a Star  Fort,  with  the 
faces  of  two  redans  prolonged 
inwards. 


lar  sites. 

1828.  The  Bastioned  Fort  has  been  designed  to  remedy  the 
defects  in  the  two  preceding  classes.  It  may  consist  of  a po- 
lygon of  any  number  of  sides,  but  for  field  forts  the  square 
and  pentagon  are  generally  prefei’red.  To  plan  a work  of  this 
kind,  a square  or  pentagon  is  first  laid  out  (Fig.  383),  and  the 

sides  bisected  by  perpendicu- 

Jk M.i — -„.F  lars.  III ; a distance,  GI,  of 

one-eighth  of  a side  in  a square 
(one-seventh  in  a pentagon)  is 
set  off  on  the  perpendiculars  ; 
from  the  angular  points  of  the 
polygon,  lines  DA.  CF,  are 
drawn  through  the  points  thus 
set  off  ; these  lines  give  the  di- 
rection of  the  lines  of  defence; 
from  the  salients  of  the  poly- 
gon, distances  equal  to  two-se- 
v^enths  of  a side  are  set  off  on 
the  directions  of  the  lines  of 
I'lG.  383.— Plan  of  a Bastioned  Fort  cou-  defence,  which  give  the  faces; 

structed  on  a square.  from  the  extremities  of  the 


NAVAL  OPERATIONS  ON  SHORE. 


673 


faces  the  flanks  are  drawn  perpendicular  to,  or  making  an  angle 
of  110°  with,  the  lines  of  defence ; the  extremities  of  the  flanks 
are  connected  by  curtains,  CD. 

1829.  In  deciding  on  the  general  plan  to  be  carried  out, 
the  following  considerations  require  attention : the  object  the 
work  is  expected  to  fulfil,  and  its  situation  with  respect  to 
the  enemy  ; whether  it  is  likely  to  be  attacked  by  overwhelm- 
ing forces;  whether  artillery  is  likely  to  he  brought  against 
it,  or  infantry;  and  whether  it  can  be  surrounded;  the  num- 
ber of  men  there  will  be  for  its  defence,  observing  that  it  is 
better  to  have  a force  concentrated,  and  that  it  is  therefore  in- 
judicious to  make  works  of  a greater  extent  than  can  be  well 
manned  and  vigorously  defended.  Another  consideration  that 
must  not  be  omitted  is  the  number  of  men  that  can  be  collected 
for  working,  whether  they  are  one’s  own  men  or  inhabitants, 
and  wliether  there  are  tools  enough  and  time  enough  to  do  it. 

1830.  Profiles. — Having  decided  on  what  is  the  best  plan  of 
the  works,  the  next  consideration  is  the  profile.  This  will  also 
depend  on  much  the  same  considerations  as  the  general  plan, 
particularly  on  the  time  in  which  the  work  is  to  be  done  and 
the  number  of  men  there  are  for  work.  A general  idea  may 
be  formed  of  the  quantity  of  work  that  may  be  performed  in  a 
given  time,  and  of  the  proportion  of  cover  that  may  be  obtained 
in  that  time,  by  adopting  different  sections  and  referring  to  the 
annexed  figures  and  cori-esponding  estimates. 

183 1.  In  ordinary  soils,  a man  can  excavate  one  cubic  yard  per 
hour  for  8 hours ; in  stiff  clay,  he  would  only  do  half  as 
much ; and  in  dry,  light  soils,  three  times  as  much.  Each  man 
should  have  6 feet  in  length  to  execute,  which  distance  enables 
him  to  use  his  tools  with  freedom ; but  when  only  improving 
the  natural  advantages  offered  by  banks,  fences,  etc.,  the  work- 
ing-parties might  be  distributed  at  much  wider  intervals  than  6 
feet ; for  instance,  a man  might  convert  20  or  30  feet  of  hedge 
into  a good  breastwork  in  three  hours,  when  he  could  not  exe- 
cute 6 feet  in  length  equally  defensible  on  a level  field. 

1832.  Fig.  384  rep- 
resents the  section  of  a 
small  trench  and  the 
parapet  that  has  been 
formed  by  throwing 
the  earth  up  in  front. 

The  trench  is  2^  feet 
deep  and  the  same 
width,  having  a rough  step  1 foot  broad  in  rear.  The  earth 
thrown  out  will  make  a parapet  of  a height  nearly  equal  to  the 


674 


NAVAL  ORDNANCE  AND  GUNNERY. 


depth  of  the  trench  without  taking  any  precautions  to  make  it 
stand  at  a steeper  slope  than  is  natural ; we  will  assume  that  is 
2 feet  high,  which  will  make  a total  of  4|-  feet  from  the  bottom 
of  the  trench.  A man,  therefore,  though  he  can  fire  over  the 
parapet,  has  to  stoop  to  be  concealed  by  it,  and  it  tlierefore 
affords  about  the  least  amount  of  protection  that  should  be 
considered.  The  solid  contents  of  the  excavation,  from  which 
the  probable  time  to  execute  it  may  be  determined,  is  found  by 
multiplying  the  depth  and  breadth  of  the  trench  together,  and 
that  product  by  the  length  each  man  has  to  do — 

Trench,  2^^  X 2-^  X 6 = 3T|-  c.  feet. 

Step,  lXlX6=G  “ 

Earth  to  be  removed  = 48-J-  “ 

Divide  this  sum  by  the  amount  excavated  in  one  hour  by  one 
man,  27  c.  feet,  and  it  will  be,  found  that  it  will  take  a little 
over  one  hour  and  a half  to  throw  up  this  parapet  on  level 
ground. 

1833.  Fig.  3S5  affords  more  cover,  for  the  top  of  the  'parapet 


is  6 feet  from  the  bottom  of  the  trench.  The  best  way  to  exe- 
cute it  would  be  to  sink  a trench  3 feet  deep  and  3 feet  wide, 
and  to  throw  the  earth  about  2 feet  in  front  of  it ; so  that,  in 
the  progress  of  the  work,  when  the  trench  became  too  deep  to 
stand  in  and  fire  over  the  parapet,  a little  step  might  be  cut  out 
of  the  solid  left  in  front  for  a bancpiette  ; another  step  in  the 
rear  would  complete  it.  The  steps  might  be  IS  inches  wide  and 
deep.  To  find  the  time  it  will  take  to  execute 

The  Trench,  3x3  X 6 = 54  c.  feet. 

Steps,  X li'  X 2 X 6 = 27  “ 

C.  feet  removed  by  one  man  per  hour,  27  )8i  “ 

It  will  require  3 hours. 

But  it  offers  no  impediment  to  an  enemy,  and  men  could  only 
he  drawn  up  in  single  file  for  its  defence. 

1834.  A trench  of  the  dimensions  shown  in  Fig.  386  might  be 
completed  in  five  hours  on  the  presumed  data,  and  being  roomy 
enough  to  dispose  men  in  double  files  for  its  defence,  and  high 


NAVAL  OPERATIONS  ON  SHORE. 


67.5 


Fig.  386. 


enoiigli  to  screen  and  cover  them,  may  be  considered  as  large  as 
is  necessary  for  merely  fulfilling  these  conditions. 

1835.  Fig.  387  is  a form  of  breastwork  that  might  be  adopted 


for  obtaining  cover  in  rocky  or  marshy  situations,  where  a ditch 
or  trench  could  not  be  made  deeper  than  two  feet ; the  men  might 
be  set  to  work  in  two  lines,  the  interior  slope  revetted  by  stakes 
or  sods,  and  it  could  be  accomplished  in  from  two  to  three 
hours. 

1836.  If  more  time  could  be  devoted  to  strengthening  a post, 
or  if  other  circumstances  were  favorable,  it  would  become  a 
consideration  whether  some  other  profile  of  a diffei’ent  form 
could  not  be  substituted  with  advantage  for  such  as  only  afford 
cover  without  opposing  an  obstacle  to  the  advance  of  an  hostile 
force,  and  this  would  properly  be  accomplished  by  excavating  a 
ditch  in  front  of  the  parapet  instead  of  making  a trench  in  rear. 

1837.  Fig.  388  shows  the  general  profile  which  such  a work 


might  have.  The  dimensions  of  the  parapet  are  determined  by  the 
following  considerations : The  height,  by  the  cover  required. 


670 


NAVAL  OEDNANCE  AND  GUNNERY. 


and  the  position  of  the  enemy  ; the  thickness,  he,  by  the  pene- 
trating power  of  the  projectiles  likely  to  be  brought  against  it. 
For  field  artillery,  15  feet  is  required ; for  rifles,  4 feet.  The  ban- 
quette, ef,  should  be  3 feet  wide,  if  for  single  rank ; 4^  feet  for 
double  rank.  In  eg,  the  banquette  slope,  the  height  is  equal  to 
lialf  the  base ; the  interior  slope,  af,  is  4|-  feet  and  steeply 
revetted  ; the  superior  slope,  ah,  is  sufflciently  sloped  to  enable 
the  lire  over  it  to  defend  the  edge  of  the  counterscarp  ; the  ex- 
terior slope,  hh,  is  left  at  the  natural  slope  at  which  unramined 
earth  will  support  itself ; the  berm.  Id,  is  made  sufflciently 
wide  to  prevent  the  earth  of  the  parapet  from  slipping  into  the 
ditch  ; the  counterscarp,  pn,  is  made  as  steep  as  the  soil  will 
permit,  and  from  6 to  12  feet  deep  ; the  scaiq),  Im,  is  not  made 
so  steep  because  it  has  to  support  the  weight  of  the  parapet : but 
both  should  be  as  steep  as  possible  to  resist  escalade.  The  ditch 
is  first  excavated  in  steps,  as  represented  in  the  figure,  which 
are  subsequently  cut  away.  The  breadth  of  the  ditch  is  thus 
determined  by  calculation : 

1838.  If  = 8 feet ; 5c  = 15  feet ; ef=  3 feet ; in  the  slope 
eg,  the  base  = height  X 2 ; in  slope  af,  the  base  = — ; in 


slope  hh,  the  base  — height ; in  the  scaiq)  Im,  the  base  = ; 

in  the  counterscaiq),  y>?^,  the  base  = — ^ — ; and  if  the  ditch  is 
to  be  10  feet  deep. 


44  + 114 

the  area,  gfoh,  X 3-|-  = 28  sq.  feet. 


aof : 


4iX  H- 


aheh  = X 15  = lOU  “ 


hek  = 


2 

X H 


= 15i  « 


Area  of  profile  of  parapet  or  ditch  = 147|-  “ 
1471 


Mean  breadth  of  ditch  = 


10 


= 14.775  feet.  Breadth  at  top 


or  bottom  of  ditch  = 14.775  ^ = 18.9  or  10.6  feet. 

^ 


NAVAL  OPERATIONS  ON  SHORE. 


677 


14:7A 

Time  required  to  execute  X 6 = nearly  33  hours.  To 

throw  up  a length  of  parapet  of  100  yards  would  require  a 
working-party  of  100  men : 50  diggers,  3d  shovellers,  16  ram- 


mers. 

1839.  Having  selected  a position  on  which  a field-work  is  to  be 
thrown  up,  and  determined  its  dimensions,  it  is  to  be  remem- 
bered that  the  salient  angles  should  be  directed  towards  points 
that  are  difficult  of  access ; the  faces  of  the  wmrk  are  then 
marked  out  by  small  pickets,  and  traced 
with  a piece  of  tape  and  the  arigles  set  off. 
To  guide  the  workmen  in  the  construc- 
tion, right  profiles  (Fig.  389),  made  with 
slips  of  board,  are  constructed  along  every  face,  about  10  yards 
apart. 

1810.  Experience  has  shown  that,  in  ordinary  soils,  a man  with 
a pick  can  furnish  employment  to  two  men  with  shovels,  and 
that,  not  to  be  in  each  other’s  way,  they  should  be  from  to  6 
feet  apart,  and,  finally,  that  a shovelful  of  earth  can  be  pitched 
by  a man  12  feet  horizontally  or  6 feet  vertically. 

1841.  To  distribute  the  workmen,  the  counterscarp  crest  is 
divided  into  lengths  of  12  feet  and  the  scarp  crest  into  lengths 
of  9 feet,  the  points  being  marked  by  pickets.  In  each  area 
thus  marked  out,  a working-party  is  arranged,  consisting  of  a 
pick  with  two  shovels  near  the  counterscarp,  two  shovels  near 
the  scarp,  and  one  man  to  spread  and  one  to  ram  the  earth  for 
two  parties.  The  pick  commences  by  breaking  ground  so  far 
from  the  counterscarp  crest,  that  by  digging  vertically  3 feet, 
he  will  arrive  at  the  position  of  the  counterscarp.  This  is 
carried  on  at  the  same  depth  of  3 feet  advancing  towards  the 
scarp,  where  the  same  precaution  is  observed.  The  earth  is 
thrown  forward  and  evenly  spread  and  rammed.  If  the  ditch  is 
deeper  than  6 feet,  an  offset,  about  4 feet  broad,  should  be  left 
at  the  scarp  at  mid-depth  of  the  ditch,  to  place  a relay  of 
shovels.  W hen  the  ditch  has  been  excavated  to  the  bottom,  the 
offsets  are  cut  away,  and  the  proper  slope  given  to  the  sides. 
The  earth  furnished  by  the  offsets,  if  not  required  to  complete 
the  parapet,  may  be  formed  into  a small  glacis.  Care  should  be 
taken  not  to  have  any  pebbles  on  top  of  the  parapet,  and  also  to 
have  a drain  to  take  the  water  off  without  letting  it  run  down 
the  scarp. 

1842.  Artillery  in  Field-works. — The  proper  positions  for 
artillery  are  on  the  flanks  and  salients  of  a work,  and  the  guns 
should  be  collected  at  these  points  in  batteries  of  several  pieces. 
The  term  battery  is  used  of  a collection  of  several  guns,  and  it 
is  named  according  as  the  parapet  is  arranged  for  firing  over  or 


Fig.  389. 


678 


NAVAL  ORDNANCE  AND  GUNNERY. 


tlirongh  it;  in  firing  over.it  is  called  a larbette  battery  - in 
firing  throngli,  an  emJjrasure  hattery. 

18d3.  The  barbette  consists  of  a mound  of  earth  thrown  up 
against  the  interior  slope ; the  upper  surface  is  level  and  1 foot 
8 inches  below  the  interior  crest ; the  earth  at  the  sides  and 
rear  receives  the  natural  slope.  To  ascend  the  barbette  a con- 
struction termed  a rainj?  is  made  of  earth  ; it  should  be  5 feet 
wide  on  top,  and  the  slope  is  G feet  of  base  to  1 of  perpen- 
dicular. It  should  be  at  some  convenient  point  in  rear,  and 
take  up  as  little  I’oom  as  possible. 

1841.  An  embrasure  is  an  opening  made  in  the  parapet  for  a 
gun  to  hre  through.  The  bottom  of  the  embrasure  is  tei'ined 
the  sole,  and  should  be  1 foot  8 inches  above  the  ground,  and 
should  slope  outward.  The  interior  opening  is  termed  the 
mouth ; it  should  be  18  inches  wide.  The  embrasure  opens 
outwards  ; the  sides  of  it  are  called  cheehs. 

1845.  Defence  of  WxVlls. — Walls  are  readily  made  available 
for  purposes  of  defence  by  loop-holing  them,  the  mode  of  doing 
it  varying  with  their  height  and  situation.  It  is  a general  rule  that 


F G.  390. — Defence  of  Walls.  6. 


loop-holes  must  be  so  placed  that  an  enemy,  if  he  succeeds  in 
rushing  up,  shall  not  be  able  to  make  use  of  them.  To  prevent 
this  they  should  be  8 or  9 feet  above  the  ground  on  the 
outside  (Fig.  390,  a),  but  on  the  inside  (Fig.  390,  V)  the 
banquette  from  which  the  defenders  are  to  lire  should  not  be 
more  than  about  4 feet  6 inches  below  them.  A portion  of 
the  wall  not  less  than  18  inches  high  should  be  left  above  the 
loop-holes  to  screen  the  men’s  heads  when  firing. 

1846.  These  points  are  attainable  in  several  ways  ; if  the  walls 
are  high,  the  loop-holes  may  be  made  near  the  top,  and  a tem- 
porary stage  or  earthen  banquette  might  be  placed  inside;  if  the 
wall  is  not  over  6 feet  high,  the  loop-holes  may  be  made  at 
4 feet  6 inches  above  the  inside  level,  and  a ditch  made  out- 


KAVAL  OPERATIONS  ON  SHORE. 


G79 


side.  The  quickest  way  of  making  a loop-hole  is  to  break  the 
wall  down  from  the  top  for  about  2 feet  (Fig.  390,  a\  and  then 
to  till  it  up  at  the  top  with  a stone  or  sand-bag.  If  the  wall 
should  be  low,  a piece  of  timber  supported  on  a couple  of  stones 
would  be  a ready  expedient.  If  exposed  to  the  tire  of  artillery, 
a wall  will  not  afford  good  cover,  but  it  may  be  improved  by 
sinking  a trench  in  rear  and  throwing  the  earth  against  the  wall, 
or  by  digging  a ditch  in  front  and  throwing  the  earth  over  the 
wall. 

1817.  Defence  of  a Building. — The  great  art  of  making  a 
defensible  post  out  of  a building  and  the  adjoining  outhouses 
and  walls,  consists  in  selecting  from  all  the  objects  in  view  only 
what  will  be  useful  in  strengthening  the  work,  and  in  sacriticing 
everything  else,  making  use  of  the  materials  for  fortifying. 

ISIS.  A building  proper  for  defensive  purposes  should  be  in  a 
commanding  position  ; it  should  be  substantial,  and  of  a nature 
to  furnish  materials  for  placing  it  in  a state  of  defence  ; it  should 
be  of  an  extent  proportioned  to  the  number  of  defenders,  and 
only  require  the  time  and  means  that  can  be  devoted  to  complet- 
ing it ; it  should  have  walls  and  projections  that  mutually  tiank 
each  other ; it  should  be  ditiicult  of  access,  and  yet  have  a safe 
retreat ; and  the  walls  should  be  of  moderate  thickness.  Brick 
houses  or  walls  are  to  be  preferred  to  those  of  stone  or  Avood. 

1 819.  The  number  of  men  necessary  for  defence  may  be  rough- 
ly estimated  by  alloAving  1 man  to  every  4 feet  on  the  loAver 
tioor,  1 to  every  6 on  the  next,  and  1 to  every  8 on  the  next. 

1850.  To  put  a building  in  condition  to  rep  1 an  immediate 
attack,  certain  points  AV'ould  naturally  claim  primary  attention, 
and  they  should  be  attended  to  in  the  order  in  Avhich  they  are 
given. 

1st.  To  collect  material  and  barricade  the  doors  and  windows 
on  the  ground  floor,  to  make  loop-holes  in  them,  and  to  level 
any  obstruction  outside  that  Avould  give  cover  to  an  enemy.  2d. 
To  sink  ditches  opposite  the  doors  on  the  outside,  and  to  arrange 
loop-holes  in  the  Avindows  of  the  upper  story.  3d.  To  loop- 
hole the  Avails,  generally  attending  first  to  the  most  exposed 
parts,  and  to  make  communications  through  all  the  Avails.  4th. 
To  place  abattis  or  any  feasible  obstructions  on  the  outside. 
5th.  To  place  out-buildings  and  garden  Avails  in  a state  of  de- 
fence, and  to  establish  communications  betAveen  them 

1851.  Defence  of  aTillage. — In  arranging  the  general  plan, 
some  substantial  buildings  Avithin  musket-range  of  each  other 
should  be  selected  for  the  prominent  or  salient  points  of  the 
line.  These,  Avith  the  intervening  Avails,  hedges,  or  open  spaces, 
will  be  prepared  for  defence  as  has  been  already  explained,  so 
as  to  completely  enclose  the  position.  Care  should  be  taken  not 


Fio.  ;{01. — Tiiic  Dfkknce  of  a 


NAVAL  OPERATIONS  ON  SHORE. 


68L 


to  attempt  to  enclose  a larger  space  than  can  be  manned  and  de- 
fended bj  the  available  force.  Anything  ■which  would  afford 
cover  to  an  enemy  outside  of  the  lines  should  he  destroyed, 
burning  houses,  filling  ditches,  throwing  down  fences,  etc.  The 
roads  by  which  an  enemy  can  approach  should  be  cut  across  by 
trenches.  All  obstructions  on  the  inside  which  are  perpendicu- 
lar to  the  line  of  defence  should  be  removed  so  as  to  admit  of 
manoeuvring.  All  streets  and  roads  open  to  attack  should  be 


barricaded,  or  breastworks  should  be  thrown  up.  If  several  bar- 
ricades are  to  be  disputed  in  succession,  the  means  of  retreat 
through  them  must  be  preserved,  and  communications  should  be 
made  from  house  to  house  on  each  side  of  the  street. 

1852.  Some  strong  building  or  buildings  should  be  selected  in 
a central  position,  commandiTig  the  principal  roads  and  streets, 
which  should  be  strengthened  and  made  to  serve  as  rallying- 
points  in  case  the  assailants  penetrate  the  outer  defences.  A 
reserve  force  should  always  be  kept  ready  to  reinforce  any  part 
of  the  walls. 


682 


NAVAL  ORDNANCE  AND  GUNNERY. 


1853.  Defence  of  a Bridge. — If  a body  of  troops  had  to  re- 
tire over  a bridge  in  the  presence  of  a superior  force,  works- 
would  naturally  be  thrown  up  in  front  of  it  for  covering  the  re- 
treat and  ensuring  its  being  held  until  the  passage  was  effected, 
and  others  might  be  placed  in  rear  for  giving  support  and  pro- 
longing the  resistance.  If  the  protection  of  the  bridge  were  the 
object,  the  same  plan  would  be  followed  ; but  if  it  were  merely 
for  disputing  the  passage  in  order  to  cover  a line  of  operations 


or  a flank  march,  works  might  be  placed  in  rear,  whicb  is  the 
proper  position  for  defensive  purposes.  The  annexed  Fig.  (393) 
may  serve  as  an  example  of  temporary  works  in  front  as  well  as 
in  rear  of  a bridge  for  guarding  and  disputing  the  passage  with 
a force  of  600  men  available  for  work  and  defence.  The  first 
consideration  should  be  the  distribution  of  the  men.  Three- 
fourths  of  them  should  be  placed  in  advance,  and  one-fourth  as 
a reserve  in  rear,  and  a small  proportion  of  the  former  number 


NAVAL  OPERATIONS  ON  SHORE. 


683 


as  a support  close  to  the  front  of  the  bridge.  A file  of  men 
should  be  allowed  to  every  yard  of  parapet  in  front,  and  the 
main  reserve  in  other  works  in  rear,  which  should  be  large 
enough  to  receive  two-thirds  of  the  whole  number,  if  the  force 
is  obliged  to  fall  back. 

1854.  This  arrangement  would  give  400  men  on  the  outer  line 
in  front,  50  men  in  rear  of  the  outer  line  as  a support,  and  150 
men  partially  occupying  the  works  in  rear  as  a reserve.  This 
would  require  200  yards  on  the  outer  line,  25  yards  for  the  sup- 
port; in  all,  225  yards  in  front. 

1855.  The  next  point  to  decide  would  be  the  plan;  and  a 
simple  and  serviceable  one  would  be  the  one  shown  in  Fig.  393, 
a priest-cap  with  a redan  on  each  face.  A ready  way  of  laying 
this  out  would  be,  first  of  all,  to  trace  a rough  semicircle  with 
pickets  about  one-sixth  less  in  running  length  than  the  required 
breastwork.  This  could  be  done  with  a radius  of  64  yards.  The 
salient  angles  being  fixed  in  the  outline  of  the  work  so  traced, 
and  their  lengths  being  disposed  within  the  semicircle  so  as 
to  flank  each  other,  the  total  length,  though  it  may  vary  with 
the  figure  adopted,  will  be  near  enough  the  required  extent  for 
practice. 

In  rear  of  the  bridge  about  200  yards  more  would  be  required, 
but  so  disposed  as  to  protect  the  men  from  enfilade. 

1856.  At  a convenient  distance  in  front,  varying  from  20  to  50 
yards,  an  abattis  or  other  obstruction  should  be  placed  parallel 
to  the  general  contour  of  the  works,  and  extending  to  the  river 
on  either  side.  This  aiTangeinent  of  the  works  would  require 
212  men  to  throw  up  the  parapet ; the  rest  might  be  emplojmd  in 
making  the  abattis,  in  throwing  down  the  parapet  walls  of  the 
bridge,  blocking  up  the  roads,  etc. 

1857.  If  the  force  be  very  ranch  smaller  the  Avorks  should 
be  executed  of  an  extent  to  correspond  ; a good  breastwork  with 
an  abattis  before  it  might  be  made  across  the  front  of  the  bridge, 
a barricade  in  the  middle,  and  another  one  in  rear  flanked  by 
strong  breastworks. 

1858.  Attack  of  Works. — Having  considered  the  various 
means  of  putting  positions  in  a state  of  defence,  it  is  in  order 
to  consider  the  various  methods  of  attacking  and  defending 
such  posts.  An  attack  should  either  be  by  surprise  or  by  open 
force. 

1859.  Surprise. — In  the  first  case  the  strictest  secrecy  should 
be  observed  as  to  the  intent : the  enemy  should  be  deceived  by 
false  manoeuvres,  and  the  troops  should  be  kept  in  ignorance  of 
the  movement  until  they  are  assembled  for  the  attack.  The 
most  favorable  moment  for  a surprise  is  about  two  hours  before 


684 


NAVAL  ORDNANCE  AND  GUNNERY. 


dayliglit.  The  troops  should  be  divided  into  a storming-party 
and  reserve,  and  the  storming-party  should  consist  of  an  ad- 
vance-party and  a support.  Several  columns  of  attack  should 
be  formed,  some  for  false  and  some  for  real  attack,  hut  the 
columns  formed  for  false  attack  should  he  strong  enough  to 
take  advantage  of  any  success. 

1860.  Pioneers  should  accompany  each  storming-party  to 
remove  obstacles,  and  they  should  be  provided  with  hags  of 
powder  with  fuses  attached  for  blowing  down  gates,  doors,  or 
other  obstructions.  All  operations  should  be  carried  on  with 
des]iatch  and  in  silence.  The  advance-party  should  he  provided 
with  ladders,  ]danks,  brush,  or  anything  which  would  be  ser- 
viceable in  tilling  up  ditches  or  crossing  them,  and  the  charges 
should  generally  be  made  in  column  through  whatever  force 
was  formed  for  the  defence  of  the  parapet.  A strong  reserve 
should  be  kept  ready  to  follow  up  any  successful  attack. 

1861.  Open  Ati'ack. — The  general  arrangements  for  an  open 
assault  comprehend  the  operations  to  gain  possession  of  the 
works,  the  measures  for  maintaining  possession,  and  the  precau- 
tions to  be  observed  in  case  of  repulse.  The  troops  should  be 
drawn  up  in  a sheltered  position  out  of  range  of  the  assailed, 
and  a heavy  fire  opened  from  the  howitzers  in  the  most  favor- 
able positions  to  enfilade  the  faces  and  destroy  all  visible  obsta- 
cles. When  the  fire  of  the  works  is  silenced,  the  troops  are 
thrown  foi’ward  and  demonstrations  made  on  several  points,  to 
divert  the  attention  of  the  assailed  fi-om  the  true  point  of 
attack,  and  to  prevent  him  from  concentrating  his  forces  there. 

1862.  The  disposition  of  the  troops  making  an  assault  will 
depend  very  much  on  circumstances;  generally,  the  parties 
should  be  arranged  as  in  the  preceding  case  ; the  troops  to  sup- 
port and,  if  necessary,  to  reinforce  the  storming-parties,  should 
advance  in  one  or  two  lines,  with  the  artillery  on  the  flanks, 
disposed  to  repel  sorties.  When  the  assailed  are  driven  from 
their  main  works  the  storming-party  should  press  them  closely, 
and  endeavor  to  enter  the  interior  works  with  them,  leaving  to 
the  troops  which  follow  the  duty  of  retaining  possession  of  the 
works  already  gained.  If  tlie  storming-party  has  to  retreat,  its 
retreat  should  be  covered  by  a strong  body  of  infantry  and 
artillery. 

1863.  Defence. — The  essential  point  in  defence  is  to  have 
every  part  of  the  works  guarded  by  a sufficient  number  of 
troops  to  resist  an  attack  on  all  sides;  this  is  of  importance,  not 
onlv  in  isolated  works,  but  in  continued  lines.  At  least  two 
ranks  should  be  drawn  up  on  the  banquette  throughout  the 
entire  extent  of  the  line,  with  supports  and  a reserve  proper- 


NAVAL  OPERATIONS  ON  SHORE. 


635 


tioned  to  the  importance  of  the  work.  The  strictest  vigilance 
should  be  exerted  to  guard  against  a surprise ; sentries  should 
be  posted  on  all  the  commanding  points  of  the  works,  and  on 
the  outside  patrols  should  be  posted  to  watch  the  enemy’s 
movements,  and  to  give  notice  of  his  approach. 

1864.  At  night  the  number  of  sentries  should  be  increased, 
and  redoubled  vigilance  should  be  used,  especially  after  mid- 
night. The  reserve  should  be  posted  in  the  most  convenient 
position  to  afford  prompt  assistance  to  any  point  in  danger  of 
being  forced.  If  the  enemy  opens  his  attack  by  a warm  can- 
nonade, the  men  should  not  be  exposed  to  it  if  they  can  be 
sheltered  at  the  posts  they  are  to  occupy  when  the  columns  of 
attack  approach.  The  men  should  be  instructed  to  reserve  their 
lire  until  the  enemy  arrives  at  certain  points  mai’ked  in  front, 
which  should  not  be  more  than  400  yards  from  the  parapet. 
Should  the  enemy  succeed  in  forcing  his  way  in,  the  reserve 
should  attack  with  the  bayonet  before  he  has  time  to  form ; but 
the  only  well-grounded  prospect  that  the  assailed  can  have  of 
repelling  the  assault,  when  tlie  enemy  has  gained  the  top  of  the 
scai’p,  is  to  meet  him  offensively  with  bayonet  on  top  of  the 
parapet.  Large  stones,  heavy  round  logs,  and  hand-grenades 
should  be  in  readiness  to  roll  over  on  the  enemy  when  he  is  in 
the  ditch. 

1865.  Sorties. — If  it  should  seem  desirable,  and  the  garrison 
is  sufficiently  strong  to  make  a sortie,  it  is  essential  that  it  should 
be  well  timed  and  vigorously  executed,  and  be  in  sufficient 
force  to  make  some  impression,  either  as  a diversion  in  favor  of 
tlie  defenders  of  the  parapet,  or  to  drive  the  assailants  back 
beyond  the  obstacles  thev  may  have  already  surmounted.  The 
party  should  be  selected  from  the  reserve,  leaving  the  parapets 
fully  manned.  The  men  for  the  sortie  shovdd  be  drawn  up 
at  the  point  where  they  are  to  go  out,  and  at  the  critical 
moment  when  the  speed  of  the  assailants  has  been  checked  by 
the  opposition  they  have  met  with  in  front,  a furious  onset 
with  the  bayonet  should  be  made  on  one  or  both  flanks,  and 
when  the  object  is  effected,  the  troops  should  immediately 
retire  within  the  works.  The  firing  from  the  defences  should 
cease  when  they  come  out,  and  be  resumed  the  moment  the 
front  is  clear  again. 

Section  VI. — The  Retreat. 

1866.  Rear-guards. — After  having  accomplished  the  objects 
of  the  expedition,  or  if  the  forces  have  been  defeated  or  re- 
pulsed, it  becomes  necessary  to  get  them  on  board  ship  as 


G86 


NAVAL  ORDNANCE  AND  GUNNERY. 


quickly  as  possible.  If  the  forces  are  at  a cousiclerable  distance 
from  the  boats,  the  retreat  will  be  a matter  requiring  great  care 
and  judgment,  particularly  if  the  rear  is  closely  pressed  by  the 
enemy  in  force.  In  this  case,  everything  will  depend  on  the 
rear-guard,  which  should  be  formed  from  the  freshest  men,  and 
should  number  at  least  one-fifth  or  oiie-sixth  of  the  whole  force, 
including  some  howitzers. 

1867.  The  great  art  of  rear-guards  is  that  of  being  able  con- 
stantly to  force  an  enemy  to  deploy  and  to  attack,  and  then  to  get 
away  safely  without  any  serious  fighting : its  pui-pose  is  more 
fulfilled  by  threatening  to  fight  than  by  fighting.  If  the  pursuing 
enemy  should  become  reckless  and  push  on  to  attack  with  an 
insufficient  force,  it  will  then  be  for  the  rear-guard  to  pounce 
suddenly  on  him  with  all  his  available  force,  and  having  struck 
a severe  blow,  to  at  once  resume  the  retreat. 

1868.  The  officer  commanding  the  main  body  should,  from 
time  to  time,  send  to  the  commander  of  the  rear-guard  infor- 
mation as  to  the  condition  of  the  road,  bridges,  etc.,  to  be 
passed,  and  every  position  suitable  for  the  rear-guard  to  defend 
itself  in  should  be  especially  noted. 

1869.  The  distance  that  the  rear-guard  should  be  from  the 
main  body  depends  upon  the  nature  of  the  country,  its  num- 
bers, and  the  manner  in  which  the  pursuit  is  conducted.  It 
should  not  be  more  than  a few  hours’  march,  and  under  all  cir- 
cumstances communication  should  be  kept  up  with  the  main 
body.  The  actual  rear  of  the  rear-guard  should  be  a line  of 
skirmishers. 

1870.  All  villages  on  the  line  of  retreat  and  all  supplies  of 
provision  should  be  destroyed ; everything,  in  fact,  on  which 
the  pursuers  might  subsist.  If  the  country  is  so  enclosed  that 
the  pursuers  must  travel  on  the  roads,  every  thing  should  be 
done  to  retard  their  progress  ; setting  fire  to  houses  or  villages 
on  the  line  of  march,  felling  trees  across  the  road,  destroying 
bridges,  should  never  be  omitted  when  it  can  be  dons. 

1871.  Destruction  of  Bridges. — Bridges  may  be  destroyed 
by  burning,  if  there  is  time ; if  not,  it  would  be  sufficient  to 
bore  a hole  in  the  main  braces  or  lower  chords  of  truss-bridges 
and  put  in  a charge  of  powder  with  a fuze.  To  destroy  a bridge 
of  masonry,  sink  a shaft  in  the  roadway  near  the  centre  arcJi, 
down  to  tiie  haunch,  with  a short  gallery  ending  in  a chamber, 
so  as  to  lodge  the  powder  in  the  middle  of  the  width  of  the 
bridge  under  the  roadway.  Five  or  six  hom-s'  labor  and  a 
charge  of  from  50  to  100  lbs.  will  probably  be  sufficient.  If 
there  is  not  time  to  sink  a deep  shaft,  a hole  may  be  sunk  across 
the  crown  of  the  arch,  and  a charge  of  250  or  300  lbs.  of  pow- 


KAVAL  OPERATION'S  ON  SHORE. 


687 


der,  placed  over  the  crown  and  covered  with  stones,  will  answer 
the  purpose. 

1872.  Passage  of  a Defile. — In  case  it  becomes  necessary 
for  the  retreating  forces  to  pass  through  a detile,  troops  from 
the  main  body  should  be  posted  on  the  heights  on  eitlier  side 
and  deployed  as  skirmishers  while  the  main  body  is  passing 
through.  As  soon  as  the  rear-guard  is  in  position  and  the 
enemy  has  deployed,  the  supports  should  enter  the  detile,  and 
the  rear-guard  should  fall  back,  maintaining  a heavy  tire  along 
the  line.  The  skirmish-line  of  the  rear-guard  should,  if  possible, 
retire  along  the  heights  as  well  as  by  the  detile  ; if  that  is  not  pos- 
sible, they  should  dispute  every  inch  of  ground  in  the  detile  while 
the  line  of  battle  is  being  formed  on  the  other  side,  howitzers 
being  posted  so  as  to  entilade  the  pass,  and  troops  ready  to 
attack  the  advance  of  the  enemy  as  they  emerge.  After  having 
given  the  enemy  a serious  check,  the  line  of  march  should  be 
resumed,  the  rear-guard  resuming  their  original  duties. 

1873.  The  Embarkation. — On  arriving  at  the  boats,  if  there 
is  no  enemy  present  or  near,  the  troops  and  howitzers  might  all 
be  embarked  at  once,  and  return  to  their  ships.  But  if  the 
enemy  is  pressing  closely,  the  breastworks  wliich  have  been 
prepared  by  the  officer  in  charge  of  the  boats  should  be  manned, 
retaining  some  howitzers  to  keep  the  enemy  at  a distance.  The 
main  portion  of  the  howitzers  should  be  embarked,  and  the 
boats  hauled  into  such  a position  that,  by  their  cross-fire,  they 
can  sweep  the  approaches  and  cover  the  embarkation  of  the 
infantry,  which  should  be  proceeded  with  as  expeditiously  as 
possible,  being  careful  to  get  all  the  howitzers  embarked  while 
there  is  still  a large  number  of  infantry  on  shore.  The  last 
who  are.  on  the  beach  should  retire  in  skirmishing  order,  keep- 
ing up  a vigorous  fire  until  the  last  moment,  when  they  should 
lose  no  time  in  getting  to  their  boats,  the  howitzers,  boats,  and 
vessels  keeping  up  a continuous  fire  to  prevent  the  enemy  from 
making  a sudden  rush  and  capturing  them. 


TABLES. 


I COEFFICIENTS  FOE  THE  CUBIC  LAW  OF 
EESISTANCE. 

ELONGATED  PROJECTILES  WITH  OGIVAL  HEADS. 


Reprinted  from  Professor  Fe.\kcis  Bashportii’ s Motion  of  Projectiles. 


V 

Kv 

K, 

s 

Log 

<y 

& 

V 

Ev 

K, 

cr 

0 

Log^A 

§ 

f-s 

900 

64.4 

2,001 

.3012 

f-s 

1300 

107.9 

3.352 

.5253 

gio 

64.8 

2.014 

.3041 

1310 

107.7 

3.345 

.5244 

920 

65-3 

2.029 

.3073 

1320 

107.4 

3.337 

.5234 

930 

65.9 

2.047 

.3111 

1330 

107.  r 

3.328 

.5222 

940 

66.6 

2.069 

.3158 

1340 

ro6.8 

3.317 

.3207 

950 

67.4 

2.094 

.3210 

1350 

106.4 

3 . 305 

.5192 

960 

68.4 

2.125 

.3274 

1360 

106.0 

3.293 

.5176 

970 

69.6 

2.162 

.3349 

1370 

105.6 

3.2S0 

.5159 

980 

71.0 

2.206 

.3436 

13S0 

105  . I 

3.265 

.5139 

990 

72.8 

2.262 

.3545 

1390 

104.6 

3.249 

.5118 

1000 

75.0 

2.330 

.3674 

1400 

104.0 

3.231 

.5093 

1010 

'77-5 

2.408 

.3817 

1410 

103.4 

3.212 

.5068 

1020 

80.4 

2.498 

.3976 

1420 

102.8 

3.193 

• S042 

1030 

83.9 

2.606 

.4160 

1430 

102.2 

3.175 

.5017 

1040 

88.2 

2.740 

.4378 

1440 

101.6 

3.155 

.4990 

1050 

92.8 

2.883 

.4598 

1450 

100.9 

3.134 

.4961 

1060 

97.2 

3.019 

.4799 

1460 

100.2 

3.112 

.4930 

1070 

100. 8 

3.131 

.4957 

1470 

99.4 

3.089 

.4898 

1080 

103.4 

3.212 

.5068 

1480 

98.7 

3.065 

.4864 

1090 

105. 1 

3.265 

.5139 

1490 

97.9 

3.041 

.4830. 

1100 

106.0 

3.293 

.5176 

1500 

97.2 

3.018 

.4797- 

mo 

io5.6 

3.312 

. 5201 

1510 

96.4 

2.994 

.4763 

1120 

107.  I 

3.327 

.5221 

1520 

95.5 

2.968 

.4725 

1130 

107.5 

3.339 

.5236 

1530 

94.7 

2.942 

.4686 

1140 

107.9 

3.351 

.5252 

1540 

93.8 

2.915 

- . 4646 

1150 

108.2 

3.361 

.5265 

1550 

93.0 

2.889 

.4607 

1160 

108.5 

3.371 

.5278 

1560 

92.2 

2.864 

.4570 

1170 

108.7 

3.377 

.5285 

1570 

91.4 

2.839 

.4533 

1180 

loS  9 

3.381 

.5290 

1580 

90.6 

2.814 

.4493 

1 190 

108.9 

3.383 

.5293 

1590 

89.8 

2.790 

.4456 

1200 

108.9 

3.383 

.5293 

1600 

89.0 

2.765 

.4417 

12x0 

108.9 

3.383 

.5293 

i6ro 

88.2 

2.740 

.4378 

1220 

108.9 

3.382 

.5292 

1620 

87.4 

2.715 

.4338 

1230 

108.8 

3.381 

.5290 

1630 

86.7 

2.693- 

.4302 

1240 

108.8 

3.380 

.5289 

1640 

86.0 

2.672 

.4268 

1250 

108.7 

3.378 

.5287 

1650 

85.4 

2.654 

.4239 

1260 

ic8.6 

3.375 

.5283 

1660 

85.0 

2.640 

.4216. 

1270 

108.5 

3.370. 

.5276 

1670 

84.6 

2.628 

.4196 

1280 

108.3 

3.364 

.5269 

1680 

84.3 

2.619 

.4181 

1290 

108. 1 

3.358 

.5261 

1690 

8.,.! 

2.613 

.4171 

1300 

107.9 

3.352 

.5253 

1700 

83.9 

2.606 

.4160 

1 


II.  COEFFICIENTS  FOE  THE  CUBIC  LAW  OF 
EESISTANCE. 

SPHERICAL  PROJECTILES. 


V 

K. 

g 

T U, 

Log 

g 

V 

K, 

Kv 

g 

L 

iLog  — 

! s 

f-s 

850 

138.4 

4.299 

• 6334 

f-S 

1250 

I5I.I 

4.694 

.6715 

860 

138.3 

4.296 

• 6331 

1260 

150.5 

4.674 

.6697 

870 

138.3 

4 

294 

.6329 

1270 

149.8 

4.654 

.6678 

880 

138.2 

4 

293 

.6328 

1280 

149.1 

4.632 

.6659 

890 

138.2 

4 

293 

.6328 

1290 

148.4 

4.611 

.6638 

goo 

138.2 

4 

294 

.6329 

1300 

147.8 

4.591 

.6619 

910 

138.3 

4 

296 

• 6331 

1310 

147.2 

4.572 

.6601 

920 

138.4 

4 

299 

.6334 

1320 

146.5 

4.552 

.6582 

930 

138.5 

4 

302 

• 6337 

1330 

145.9 

4.533 

.6564 

940 

138.6 

4 

306 

• 6341 

1340 

145.3 

4.514 

.6546 

950 

138.8 

4 

312 

■ 6347 

1350 

144.7 

4.495 

.6527 

960 

139-1 

4 

322 

• 6357 

1360 

144.1 

4.475 

.6508 

970 

139.5 

4 

334 

.6369 

1370 

143.4 

4.455 

.6489 

980 

139.9 

4 

346 

.6381 

1380 

142.7 

4.433 

.6467 

990 

140.4 

4 

362 

• 6397 

1390 

142.0 

4.410 

.6444 

1000 

I4I  . I 

4 

383 

.6418 

1400 

141.3 

4.388 

.6423 

1010 

141.9 

4 

408 

.6442 

1410 

140.6 

4.366 

.6401 

1020 

142.8 

4 

436 

.6470 

1420 

139.8 

4.343 

.6373 

1030 

143.8 

4 

467 

.6500 

1430 

139. 1 

4.320 

•6355 

1040 

144.9 

4 

501 

• 6533 

1440 

138.4 

4.299 

•6334 

1050 

146.1 

4 

539 

.6570 

1450 

137.7 

4.277 

.6311 

1060 

147.3 

4 

576 

.6605 

1460 

137.0 

4.254 

.6288 

1070 

148.5 

4 

613 

.6640 

1470 

136.2 

4.231 

.6264 

1080 

149.6 

4 

647 

.6672 

1480 

135.5 

4.209 

.6242 

1090 

150.6 

4 

677 

.6700 

1490 

134.8 

4. 188 

.6220 

noo 

151.4 

4 

703 

.6724 

1500 

134.1 

4.166 

■6197 

IIIO 

152.1 

4 

725 

-6744 

1510 

133.5 

4.146 

.6176 

1120 

152.7 

4 

744 

.6762 

1520 

132.8 

4.125 

•6154 

,1130 

153.1 

4 

757 

.6773 

1530 

132.1 

4.105 

.6133 

1140 

153.4 

4 

766 

.6782 

1540 

131.5 

4.0S5 

.6112 

1150 

153.6 

4 

772 

.6787 

1550 

130.8 

4.064 

.6090 

-1 160 

153.7 

4 

774 

.6789 

1560 

130.1 

4.043 

.6067 

1 1 70 

153.7 

4 

775 

.6790 

1570 

129.5 

4.023 

.6046 

1180 

153.7 

4 

774 

.6789 

1580 

12S.8 

4.003 

.6024 

JI9O 

153.6 

4 

771 

.6786 

1590 

128.2 

3.983 

.6002 

II 200 

153.4 

4 

765 

.6781 

1600 

127.5 

3.961 

•5978 

1210 

153.1 

4 

756 

.6772 

i6io 

126.8 

3.940 

-5955 

1220 

152.7 

4 

744 

.6762 

1620 

126.2 

3.920 

-5933 

1I23O 

152.2 

4 

728 

.6747 

1630  : 

125.5 

3.899 

.5910 

1240 

151.7 

4 

*712 

.6732 

1640 

124.8 

3.877 

.5885 

II25O 

151.1 

4 

694 

.6715 

1650  1 

124.  I 

3.856 

.5861 

2 


V 

K. 

g 

Log  _I 

s 

V 

K. 

g 

Log  ^ 
g 

f-S 

1650 

124.  I 

3.856 

.5861 

f-S 

1900 

108.7 

3.377 

.5285 

1660 

123.5 

3.836 

• 5839 

1910 

108.2 

3.361 

• 5265 

1670 

. 122.8 

3.815 

• 5815 

1920 

107.7 

3.346 

• 5245 

1680 

122. 1 

3.793 

• 5790 

1930 

107.3 

3.332 

• 5227 

1690 

I2I.4 

3.772 

.5766 

1940 

106.8 

3.317 

.5208 

17CX1 

120.8 

3.752 

.5743 

1950 

106.3 

3.302 

.5188 

1710 

120.  r 

3.731 

.5718 

i960 

105.8 

3.287 

.5168 

1720 

119.4 

3.710 

.5694 

1970 

105.3 

3.272 

.5148 

1730 

118.8 

3.689 

.5669 

I9S0 

104.9 

3.258 

.5130 

1740 

118.1 

3.669 

.5646 

1990 

104.4 

3.243 

.5110 

1750 

117.4 

3.648 

.5621 

2000 

103.9 

3.228 

.5089 

1760 

116.8 

3.628 

• 5597 

2010 

103.4 

3.212 

.5068 

1770 

116.1 

3.608 

• 5573 

2020 

102,9 

3.197 

• 5047 

1780 

115.5 

3.588 

• 5549 

2030 

102,5 

3.183 

.5028 

1790 

114.9 

3.568 

• 5524 

2040 

102.0 

3.169 

.5009 

i8oo 

1 14. 2 

3.548 

• 5500 

2050 

101.5 

3.154 

.4989 

1810 

113.6 

3.529 

•5477 

2060 

lOI . I 

3.140 

.4969 

1820 

113.0 

3.511 

•5454 

2070 

100.6 

3.125 

•4949 

1830 

112.5 

3.494 

•5433 

2080 

100. 1 

3. no 

.4928 

1840 

111,9 

3.476 

• 5411 

2090 

99.7 

3.096 

.490S 

1850 

III. 3 

3.459 

•5390 

2100 

99.2 

3.081 

.4887 

i860 

no. 8 

3.442 

• 5363 

2110 

98.7 

3.066 

.4866 

1870 

no. 3 

3.425 

• 5347 

2120 

98.3 

3.053 

.4847 

1880 

log. 7 

3.408 

• 5325 

2130 

97.8 

3.039 

.4827 

1890 

109.2 

3.392 

• 5305 

2140 

97.4 

3.025 

.4807 

1900 

108.7 

3.377 

• 52S5 

2150 

96.9 

3.010 

.4786 

III.  Log  V(p  = Log  (3  tan  <p  tan  ^(f). 


Log 

Log 

LogP^ 

LogP^ 

0 

0 

1 

0 

I 

8.71909 

r6 

9.94636 

31 

0.30525 

46 

0.62501 

2 

9.02038 

17 

9-97579 

32 

0.32605 

47 

0.64839 

3 

9.19691 

18 

0.00392 

33 

0.34676 

48 

0.67226 

4 

9.32247 

19 

0.03093 

34 

0.36743 

49 

0.69666 

5 

9.42018 

20 

0.05695 

35 

0.38809 

50 

0.72164 

6 

9-50034 

21 

0.08212 

36 

0.40S77 

51 

0.74725 

7 

9.56844 

22 

0. 10654 

37 

0.42952 

52 

0.77355 

8 

9.62777 

23 

0.  i-^o'io 

38 

0.45037 

53 

0.80059 

9 

9.68045 

24 

0.15349 

39 

0.47135 

54 

0.S2S44 

10 

9.72792 

25 

0. 17618 

40 

0.49250 

55 

0.85717 

II 

9.77121 

26 

0. 19844 

41 

0.51385 

56 

0.886S5 

12 

9.81109 

27 

0.22033 

42 

0.53545 

57 

0.91755 

13 

9.84813 

28 

0.2^191 

43 

0.55732 

58 

0.94937 

14 

9.8S280 

29 

0.26322 

44 

0.57951 

59 

0.98239 

15 

9-91545 

30 

0.28432 

45 

0.60206 

60 

1.01671 

3 


lY.  VALUES  OF  X,  y & T FOE  IXTEEYALS  OF  0°2. 


y 

= 0.00 

r = 

O.OI 

9 

X 

Y 

T 

X 

Y 

T 

0 

6o.o 

1.73205 

I . 50000 

1.73205 

0 

60.0 

1.77949 

I . 55885 

I - 75552 

59-8 

1.71818 

I . 47606 

1.71818 

59-8 

1-76457 

1-53311 

I. 741 12 

59-6 

I . 70446 

1-45259 

I . 70446 

59-6 

1.74984 

I . 50791 

I . 72691 

59-4 

1.69091 

1.42959 

1.69091 

59-4 

1-73530 

1.48323 

1.71288 

59-2 

1.67752 

1.40703 

1.67752 

59-2 

I . 72096 

1.45906 

I . 69902 

59-0 

1.66428 

1.38492 

1.66428 

59-0 

I . 70679 

1-43539 

1.68533 

58.8 

1.65120 

1.36322 

1.65120 

58.8 

1.69281 

I.4I22I 

1.67180 

58.6 

1.63826 

I -34195 

1.63826 

58.6 

1.67899 

1.38949 

1.65843 

58.4 

1.62548 

I. 32109 

1.62548 

58.4 

1.66535 

1.36723 

1.64523 

58.2 

1.61283 

I . 30062 

1.61283 

58.2 

1.65188 

I • 34542 

1.63218 

58.0 

I . 60033 

1.28054 

1.60033 

58.0 

1-63857 

I . 32404 

1.61928 

57.8 

1-58797 

I . 26083 

1-5S797 

57.8 

1-62543 

I . 3030S 

1.60653 

57-6 

1-57575 

I. 24149 

1-57575 

57-6 

1.61244 

1.28253 

1-59393 

57-4 

I . 56366 

I. 22251 

1.56366 

57-4 

I . 59960 

1.26238 

1-58147 

57.2 

1-55170 

1.20388 

1-55170 

57-2 

1.58691 

I . 24262 

1.56915 

57-0 

1-53987 

1.18559 

1-53987 

57-0 

1-57437 

1.22324 

1-55697 

56.8 

1.52816 

I . 16764 

I . 52816 

56.8 

1.56198 

1.20423 

1-54493 

56.6 

1.51658 

I. I 5001 

1.51658 

56.6 

I • 54973 

1.1855S 

1.53302 

56.4 

I. 50512 

I . 13270 

I. 50512 

56.4 

1.53762 

1.16728 

I. 52124 

56.2 

1.49378 

I .11569 

1.49378 

56.2 

1-52564 

I. 14932 

1.50958 

56.0 

1.48256 

1.09899 

1.48256 

56.0 

1.51380 

1.13170 

I .49806 

55-8 

1.47146 

1.08259 

1.47146 

55-8 

I . 50209 

I. I 1440 

1.48665 

55-6 

I . 46046 

I . 06648 

I . 46046 

55-6 

1.49051 

1.09742 

I -47537 

55-4 

1.44958 

1.05065 

1.44958 

55-4 

1.47905 

1.0S075 

1.46420 

55-2 

1.43881 

1.03509 

1.43881 

55-2 

1.46772 

1.06438 

I-45315 

55-0 

I .42815 

1.01980 

1.42815 

55-0 

1.45651 

1.04831 

1.44222 

54-8 

I. 41759 

1.00478 

1-41759 

54.8 

I -44541 

1.03253 

1-43140 

54.6 

I -40714 

. 99002 

I. 40714 

54-6 

1-43444 

I. 01 703 

1.42068 

5f4 

1.39679 

-97550 

1.39679 

54-4 

1.42357 

i.ooiSo 

1.4100S 

54-2 

1-38653 

.^6124 

1-38653 

54-2 

I .41282 

.98684 

1-39958 

54-0 

1-37638 

.94722 

1-37638 

54-0 

I .40219 

-97214 

1.38919 

53-8 

I - 36633 

•93343 

1.36633 

53'- 8 

1.39165 

•95770 

1.37S90 

53-6 

1-35637 

.91987 

1.35637 

53-6 

1.38123 

•94351 

1.36871 

53-4 

1.34650 

•90653 

1-34650 

53-4 

I. 37091 

.92956 

1.35862 

53-2 

1-33673 

.89342 

1-33673 

53-2 

I . 36069 

•91585 

1-34863 

53-0 

I .32704 

.88052 

1.32704 

53-0 

1-35058 

.9023S 

1-33873 

52-8 

I -31745 

.86783 

1-31745 

52.8 

1.34056 

.88914 

1.32891 

52.6 

1-30795 

•85536 

1-30795 

52.6 

1.33064 

.87612 

1.31921 

52-4 

1.29853 

.84309 

1.29853 

52.4 

1.32071 

.86332 

1.30959 

52.2 

1.28919 

.83102 

1.28919 

52.2 

1.31108 

•85073 

1.30007 

52.0 

1.27994 

.81913 

1.27994 

52.0 

I. 30144 

•83834 

I . 29063 

51-8 

1.27077 

•80743 

1.27077 

51.8 

1.29189 

.82616 

1.28127 

51-6 

1.26169 

•79592 

1.26169 

51-6 

1.28243 

.81418 

1.27200 

51-4 

1.25268 

.78460 

1.2526S 

51-4 

I . 27306 

. 80240 

1.26282 

51.2 

1 

1-24375 

•77346 

1-24375 

51-2 

1.2637S 

.790S1 

1.25371 

4 


y = 0.02 


Y = 0.03 


9 

X 

Y 

T 

X 

Y 

T 

U 

60.0 

1.83254 

1.62567 

1.78117 

0 

60.0 

1 1.89266 

I . 70264 

1.80950 

59.8 

1.81636 

1-59774 

1.76618 

59-8 

1.87490 

1.67200 

1.79380 

59-6 

I . 80041 

1.57045 

1-75139 

59-6 

! 1-85743 

1.64211 

1.77832 

59-4 

I . 78468 

1.54376 

1.73680 

59-4 

1.84025 

1.61294 

I . 76306 

59-2 

1.76919 

1.51766 

1-72239 

59-2 

1-82334 

I . 58447 

I . 74802 

59.0 

I-7539I 

I. 49213 

1.70817 

59-0 

1.80671 

1-55667 

1.73318 

58.8 

1.73885 

1.46716 

1-69413 

58.8 

1-79033 

1-52952 

1.71854 

58.6 

1.72399 

1-44273 

1.68027 

58.6 

I. 77421 

I . 50301 

I . 70410 

58.4 

1.70934 

1.41882 

1.66658 

58.4 

1-75833 

I. 47710 

1.68985 

58.2 

1.69488 

I. 39541 

1.65306 

58.2 

I . 74270 

1.45178 

1.67579 

58.0 

I .6S062 

1.37250 

1.63971 

58.0 

1.72729 

1.42703 

1.66191 

57-S 

1.66655 

1-35007 

1.62652 

57.8 

I . 7I2II 

I. 40283 

1.64822 

57-6 

1.65266 

1.32S10 

1.61349 

57.6 

1.69716 

I. 37917 

1-63469 

57-4 

1.63896 

1.30658 

I . 60062 

57.4 

1.68241 

1.35603 

1.62134 

57-2 

1.62542 

1.28550 

1.58790 

57-2 

1.66788 

1-33339 

1.60S15 

57-0 

1.61206 

1.26485 

1.57533 

57.0 

1-65355 

.1-31123 

I -59513 

56.8 

1.59S87 

I .24461 

1.56290 

56.8 

1.63941 

1-28955 

1.58227 

56.6 

1.58584 

1.22478 

1.55062 

56.6 

1.62547 

1.26833 

1.56956 

56-4 

1.67298 

1-20534 

1-53847 

56.4 

1.61172 

1-24755 

I -55701 

56.2 

I . 56027 

1.18628 

I . 52647 

56.2 

1-59815 

I. 22721 

I . 54461 

56.0 

I -54771 

1.16759 

1.51460 

56.0 

1.58476 

1.20728 

I - 53235 

55-8 

1-53530 

I. 14927 

1.50286 

55.8 

I -57154 

1.18776 

1.52023 

55.6 

1.52304 

1.13130 

I. 49125 

55.6 

1-55850 

I . 16864 

1.50S26 

55-4 

1-51093 

1.11367 

1-47977 

55.4 

1.54562 

I . r46go 

I . 49642 

55-2 

1.49895 

1.09638 

1.46841 

55-2 

1.53291 

1-13154 

1.48472 

55-0 

1.48712 

I. 07941 

1-45718 

55-0 

1-52035 

1-11354 

I -47315 

54-8 

1-47542 

1.06276 

I . 44607 

54.8 

1-50795 

1.09589 

1.46171 

54-6 

1-46385 

I . 04642 

1.43507 

54.6 

1.49570 

1.07859 

1-45039 

54-4 

I. 45241 

1.03038 

I. 42419 

54.4 

1.48360 

1.06163 

I .43920 

54-2 

I. 44109 

1.01464 

I. 41342 

54-2 

1.47164 

1.04499 

1.42813 

54-0 

1.42991 

.99918 

1.40276 

54-0 

1.45983 

1.02867 

1.41718 

53.8 

1.41884 

.98401 

I. 39221 

53-8 

1.44815 

1.01266 

1.40634 

53-6 

1 1.40785 

.96911 

1.38177 

53-6 

1.43661 

-99694 

1.39562 

53-4 

I - 39706 

.95447 

1.37143 

53-4 

1.42521 

-98153 

1.3S501 

53-2 

1.38635 

.94010 

1.36120 

53-2 

I -41393 

. . 96640 

1-37452 

53-0 

1-37575 

.92598 

1-35107 

53-0 

1.40278 

-95155 

1-36413 

52.8 

1.36526 

.91211 

I -34104 

52.8 

I. 39175 

.93697 

1-353S5 

52.6 

! 1-35488 

.89848 

1.33111 

52.6 

1.38085 

.92266 

1-34367 

52.4 

I . 34460 

.88509 

1 .32127 

52.4 

1.37007 

.90860 

I - 33359 

52.2 

1-33442 

.87192 

1.31152 

52.2 

1-35940 

.89480 

1.32361 

52.0 

1-32435 

.85898 

1.30187 

52.0 

1-34885 

.88125 

1-31372 

51.8 

1.31438 

.84627 

I. 29231 

‘51-8 

1-33841 

.86794 

1-30393 

51.6 

1-30451 

-83378 

I. 28284 

51-6 

1.32S08 

.85486 

I . 29424 

51-4 

I . 29474 

.82149 

1.27346 

51-4 

1.31786 

.84201 

1.28465 

51-2 

1.28506 

. 80941 

1.26416 

51-2 

1-30774 

.82938 

1-27515 

51.0 

1.27548 

.79753 

1.25494 

51-0 

1.29773 

.81697 

1.26574 

50.8 

1.26598 

-78585 

I . 24581 

50.8 

1.28782 

-80477 

1.25642 

50.6 

1.25658 

-77436 

1.23676 

50.6 

1.27801 
i , 

.7927S 

1.24718 

5 


y = 

= 0.04 

7 = 

0.05 

^ 1 

X 

Y 

T 

X 

Y 1 

i 

m 

X 

0 

6o.o 

1.96194 

1.79302 

1.84116 

“ i 
60.0 

2.04361 

I .90178 

1.87718 

59-8 

1.94216 

1.75889 

1-82459 

59.8 

2.02II2 

1.86297 

1.85951 

59-6 

1.92275 

1.72568 

I . 80828 

59-6 

I -99913 

1-82535 

1.84215 

59-4 

1.90372 

1.69336 

1.79222 

59-4 

1.97764 

1.78886 

1.82509 

59-2 

1.88503 

I .66189 

I . 77640 

59-2  [ 

1.95662 

1-75346 

1.80831 

59-0 

I . 86669 

1.63124 

1.76082 

59-0 

1.93605 

1.71908 

I . 79181 

58.8 

1.84867 

I .60138 

I . 74546 

58.8 

1.91591 

1.68569 

1-77557 

58.6 

1.83097 

1.57227 

1-73033 

58-6  ! 

1.89618 

1.65325 

1.75960 

58.4 

1.81358 

1.54388 

I. 71543 

58-4 

1.87685 

1.62170 

1.74388 

58.2 

I . 79648 

1.51620 

I . 70072 

58.2 

1.85790 

1. 59102 

1.72S40 

58.0 

1.77967 

1.48920 

1.68623 

58.0 

1.83932 

1.56116 

1.71316 

57-8 

1.76314 

1.46284 

1.67193 

57-8 

1.82108 

I. 53210 

1.69814 

57-6 

I . 74688 

I. 43712 

1-65783 

57-6 

1.70619 

1-50379 

1.68336 

57-4 

1.73088 

I.412OI 

1.64392 

57-4 

1-7S563 

1.47622 

1.66878 

57-2 

1.71513 

1.38748 

1.63020 

57-2 

1.76S38 

1 - 44935 

1.65442 

57-0 

1.69963 

1-36351 

I .61666 

57-0 

I- 75143 

1.42316 

I . 64026 

56.8 

1.68437 

I. 34010 

I .60329 

56.8 

1-73478 

1.39762 

I . 62630 

56.6 

1.66933 

1.31721 

I. 59010 

56.6 

1.71842 

1.37270 

1-61253 

56.4 

I- 6545 3 

1.29484 

I -57707 

56-4 

1 1.70233 

1-34839 

I . 59S95 

56.2 

1.63994 

1.27292 

I . 56421 

56-2 

1.68650 

I . 32466 

1.58556 

56.0 

1.62556 

1-25157 

1-55151 

56.0 

1.67003 

I. 301 50 

1-57234 

55.8 

1.61139 

I . 23064 

1-53897 

55-8 

1.65562 

1.27887 

1-55930 

55-6 

I . 59742 

I.2IOI7 

1-52657 

55-6 

1.64054 

1.25677 

I • 54643 

55-4 

1-58365 

1-19013 

I -51433 

55-4 

1.62570 

1-23517 

1-53372 

55-2 

1.57007 

1.17051 

1.50224 

55-2 

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I. 2 1407 

1.52117 

55-0 

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1.15130 

1.49029 

55-0 

1.59669 

I - 19344 

1.50S78 

54-8 

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I. 13250 

1-47847 

54-8 

1 1.58251 

1-17326 

1-49655 

54-6 

1.53042 

I . 1140S 

I .46680 

54-6 

1 1-56854 

1-15353 

1 . 48-146 

54-4 

1-51755 

I . 09604 

1.45526 

54-4 

1 1-55477 

I -13423 

1-47253 

54-2 

1.50485 

1-07837 

1-44385 

54-2 

j I- 54120 

1-11534 

1.46073 

54-0 

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I 1.52782 

1.096S6 

1.44908 

53.8 

1.47994 

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I .42141 

53-8 

1-51463 

1.07877 

1 .43756 

53-6 

1.46772 

1.02744 

1.41038 

53-6 

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1.06105 

1.42617 

53-4 

1-45565 

I.OIII3 

I . 39946 

53-4 

1 1.48S7S 

1.04370 

I. 41492 

53-2 

1-44373 

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53-2 

1 1.47612 

1.02671 

1.403S0 

53-0 

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1-37799 

53-0 

j 1.46362 

1.01007 

1.392S0 

52.8 

1.42032 

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1.36743 

52-8 

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52.6 

I .40SS2 

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1-35698 

52.6 

1.43911 

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1.37116 

52.4 

I . 39746 

-93417 

I . 34664 

52-4 

1.42709 

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1.36052 

52.2 

1.38624 

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1.33640 

52.2 

I. 41522 

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1-34999 

52.0 

1-37514 

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1.32626 

52.0 

I -40351 

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1-33953 

51.8 

1-36417 

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1.31623 

51-8 

I. 39194 

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1.3292S 

51.6 

1-35332 

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1.30630 

51.6 

1.38051 

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, I -31909 

51.4 

I .34260 

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I . 29647 

51-4 

1.36921 

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I. 30901 

51-2 

I. 33199 

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1.2S674 

51-2 

1.35S04 

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, 1.29903 

51.0 

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1.27711 

51.0 

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; 1.2S914 

50.8 

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1.26757 

50.8 

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1 1-27935 

50.6 

1.30085 

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1.25812 

1 50-6 

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1 1.26966 

6 


y — o.o6  I y=  0.07 


9 

X 

Y 

T 

X 

Y 

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0 

60.0 

i 

2.14308 

2.03739 

1.91913 

0 

60.0 

2.27039 

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1.96977 

59-8 

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1.89999 

59-8 

2.23783 

2.15980 

1.94851 

59-6 

2.09106 

1.94799 

1.88124 

59-6 

2.20652 

2.10621 

1.92779 

59-4 

2.06613 

1.90568 

1.86386 

59-4 

2.17634 

2 . 05498 

1-90757 

59-2 

2.04187 

1.86482 

I . 84484 

59-2 

2.14722 

2.C0594 

1.8S782 

59-0 

2.01825 

I. 82534 

1.82716 

59.0 

2.11908 

1.95891 

1.86852 

58.8 

1.99522 

1.78717 

I . 80980 

58.8 

2.09184 

1.91376 

I . 84964 

58.6 

1.97276 

1.75023 

I . 79276 

58.6 

2.06545 

1.87036 

1.83117 

58.4 

1.95084 

I- 71445 

1.77601 

58.4 

2.03986 

1.82859 

1.81308 

58.2 

1.92943 

1.67979 

1-75956 

58.2 

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1.78835 

1-79535 

58.0 

1.90851 

1.64619 

1 • 74339 

58.0 

1.99085 

r- 74955 

1.77798 

57-8 

1.88806 

1.61359 

1.72749 

57-8 

1.96736 

I. 71209 

I . 76093 

57-6 

1.86806 

1.58194 

1.71186 

57-6 

1.94448 

1.67591 

I- 74421 

57-4 

I . 84848 

1.55121 

1.69647 

57-4 

1.92220 

I . 64092 

1.72780 

57-2 

1.82931 

1-52135 

1.68133 

57-2 

I . 90046 

1.60707 

I . 71167 

57-0 

1.81053 

1-49233 

I . 66642 

57-0 

1.87926 

1-57430 

1.69584 

56.8 

I. 79213 

I .46410 

1-65175 

56.8 

1.85856 

1.54254 

1.68027 

56.6 

1.77409 

1.43663 

1.63729 

56.6 

1-83833 

1-51175 

I .66497 

56.4 

1-75639 

1.40990 

1.62306 

56.4 

I .81857 

I .4S188 

1.64991 

56.2 

I • 73903 

1.38386 

I . 60902 

56.2 

I . 79923 

1.45289 

1.63511 

56.0 

I. 72199 

1-35850 

1.59520 

56.0 

1.78031 

1-42473 

1.62054 

55.8 

1.70526 

1-33379 

1.58156 

55-8 

1.76179 

1-39733 

1.60620 

55-6 

1.68883 

I . 30970 

1.56812 

55-6 

I . 74365 

I . 37078 

1.59207 

55-4 

1.67268 

I . 2S621 

1-55487 

55-4 

1.72587 

I . 34491 

1.57816 

55-2 

1.65682 

1.26330 

1.54180 

55-2 

I . 70S44 

1-31974 

I . 56446 

55-oj 

1.64122 

I . 24094 

1.52890 

55-0 

1-69135 

1.29524 

1.55096 

54-8 

1.62588 

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1.51617 

54-8 

1-67458 

1.27138 

1-53766 

54-6 

1.61079 

I . 19780 

1.50361 

54-6 

1.65812 

1.24813 

1-52454 

54-4 

1-59595 

1.17699 

I .49122 

54-4 

1.64196 

1.22548 

I. 51161 

54-2 

1.58134 

1.15666 

1.47898 

54-2 

1.62609 

1.20339 

1.49885 

54-0 

1.56696 

r. 13679 

I . 46690 

54-0 

1.61049 

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1.48627 

53-8 

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53-8 

i-595y 

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1.47386 

53-6 

1-53885 

1.09839 

1.44318 

53-6 

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I. 14032 

1.46161 

53-4 

1.52512 

1.07983 

1-43154 

53-4 

1.56529 

I . 12030 

r- 44952 

53-1 

1.51158 

1.06167 

1.42004 

53-2 

1-55071 

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1-43758 

53-0 

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1.04390 

1.40867 

53-0 

1-53638 

I .0S165 

1.42580 

52.8 

I .48509 

1.02652 

1-39744 

52-8 

I . 52227 

I .06299 

1.41417 

52.6 

1-47213 

1.00950 

1.38634 

52-6 

1.50838 

1.04475 

1.40268 

52.4 

1-45935 

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1-37537 

52-4 

1.49470 

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52.2 

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1.38011 

52.0 

I. 43431 

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1-35379 

52.0 

1.46794 

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I . 36902 

51.8 

1.42204 

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1.45486 

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51-6 

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51-6 

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50.8 

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1.29186 

50.8 

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50.6 

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50.6 

1.38018 

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I . 29497 

7 


y — 0.08 


y = 0.09 


X 

Y 

T 

1 ^ 

X 

Y 

1 T 

0 

60.0 

2.44854 

2.47491 

2.03488 

u 

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1.96302 

58.4 

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2.18144 

I. 91249 

59-2 

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58.2 

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1.89013 

59-0 

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2.13716 

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58.0 

2.22605 

2.05726 

1.86850 

58.8 

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58.4 

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1-97579 

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57-4 

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1.80738 

58.2 

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1.83767 

57-2 

j 2.09316 

1.84775 

1.78812 

58.0 

2.09255 

1.88037 

1.81862 

57-0 

2.06336 

I. 80168 

1-76934 

57-8 

2.06455 

1-83573 

I . 80002 

56.8 

2.03470 

1-75770 

1.75102 

57-6 

2.03749 

I . 79292 

1.78183 

56.6 

2.00707 

1.71564 

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57-4 

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1-75182 

I . 76404 

56.4 

1 . 98040 

1-67535 

1.71566 

57-2 

1.98594 

1-71231 

I . 74662 

56.2 

1.95462 

1.63670 

1.69856 

57-0 

1.96134 

1.67428 

1.72956 

56.0 

1.92967 

1.59956 

1.68182 

56.8 

1-93745 

1.63764 

1.71284 

55-8 

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1.56384 

1.66544 

56.6 

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1.60230 

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55-6 

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56.4 

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56.2 

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S 


y — O.  lO 


y — o.  1 1 


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X 

Y 

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9 

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0 

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1.39921 

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1.27493 

48.4  i 

I .36616 

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1.23746 

49.2 

1.38607 

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1.26454 

48.2  I 

I. 35319 

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1.22734 

49.0 

1.37315 

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48.0 

I . 34042 

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1.21734 

48.8 

I . 36042 

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I . 24414 

■ 47.8 

1.32785 

.78737 

I . 20746 

48.6 

1.34788 

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1.23412 

47.6 

1.31547 

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1.19769 

9 


7=0.  12  I 7=0.  13 


9 \ 

X 

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56.0 

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2.16734 

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54-8 

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1.75868 

55-6 

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1.71201 

55-2 

2.17357 

1.86719 

I . 74020 

54-2 

2.13441 

1.77922 

1 . 69040 

55-0 

2.I32IO 

1-80775 

1. 71917 

54-0 

2.09231 

I .72105 

1-66973 

54-8 

2.09331 

1.75256 

1.69894 

53.8 

2.05309 

1.66727 

1 . 64987 

54-6 

2.05683 

1.70103 

1.67941 

53-6  [ 

2.01633 

1.61722 

1.63074 

54-4 

2.02237 

1.65271 

1.66052 

53-4  1 

1.98169 

1-57041 

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54-2 

1.98967 

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1.56419 

I . 62444 

53-0 

I. 91777 

1-48495 

1 • 57699 

53-8 

1.92882 

1.52344 

1.60715 

52.8 

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1-44571 

I . 56011 

53-6 

1.90037 

1.48471 

1 . 59032 

52.6 

1.85972 

1 . 40846 

1-54369 

53-4 

1.87307 

1.44781 

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52.4 

1.83253 

1-37303 

1-52769 

53-2 

1.84682 

1.41260 

1-55789 

52.2 

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I . 30698 

1.49683 

52.8 

I. 79714 

1 . 34666 

1 . 52694 

51.8 

1.75708 

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1.48193 

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52.4 

1.75074 

1.28596 

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1.42538 

51.8 

1.68634 

1.20322 

1.45504 

50.8 

; 1-64734 

1.13903 

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51-6 

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1.64637 

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1.08318 

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1.55238 

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1.34821 

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1.36482 

49-4 

1-51763 

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1.01981 

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49-0 

1-48445 

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1.50506 

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48. S 

; 1.46840 

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49.6 

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1.31764 

48.6 

; 1.45269 

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1 .27828 

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48.4 

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48.6 

1.41403 

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1.26234 

47-6 

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I.2244S 

48.4 

1.39985 

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47-4 

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48.2 

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1.35106 

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1 . 20395 

48.0 

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1-33759 

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1.35880 

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46.8 

i 1-32435 

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45.6 

1 - 24939 

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1 . 12666 

10 


y 

= 0,14 

y = 

0.15 

9 

X 

Y 

T 

9 

X 

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0 

54-0 

2.30632 

1.98239 

1.73297 

U 

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2 . 24268 

1.89511 

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1.79555 

1.65629 

53-6 

2.18662 

1.81878 

I . 68405 

52.6 

2.13738 

I. 72197 

1.63321 

53-4 

2.13627 

1.75073 

1.66177 

52.4 

2.09724 

1.65662 

1.61148 

53-2 

2.09040 

1.68919 

1.64059 

52.2 

2.04169 

1.59768 

1 . 59086 

53-0 

2.04816 

1.63293 

I .62037 

52.0 

1.99983 

I. 54391 

1.57118 

52.8 

2.00893 

1.58106 

I . 60097 

51.8 

1.96103 

1.49442 

1.55232 

52.6 

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1.53290 

1.58230 

51.6 

1.92480 

1.44854 

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1.48795 

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51.4 

I . 89076 

1.40575 

1.51667 

52.2 

1.90516 

1.44578 

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1.85864 

1.36565 

1.49973 

52.0 

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1.82819 

I. 32791 

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51.8 

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1.51350 

50.8 

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1.29226 

1.46737 

51.6 

1.81672, 

1.33295 

1.49752 

50.6 

1.77157 

1.25849 

1.45186 

51.4 

1.78982 

I. 29913 

1.48195 

50.4 

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I . 22640 

1.43675 

51.2 

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1.73918 

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1.69536 

1.16667 

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50.8 

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1.43746 

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49.4 

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1.38250 

49.0 

1.58558 

1.03806 

1.34024 

49.8 

1.60706 

1.07632 

1.36943 

48.8 

1.56566 

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1.32756 

49.6 

1.58734 

1.05306 

1.35660 

48.6 

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47.8  j 

1.47397 

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I . 30660 

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1.32920 

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I . 16720 

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45.0 

I . 26697 

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45.8  ; 

1.2S945 

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1.25421 

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44.6 

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45.4  ! 

I . 26409 

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1.12873 

44.4 

1.22935 

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44.2 

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1.08457 

45.0 

1.23959 

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1.11015 

44.0 

I. 20531 

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1-07558 

44.8  i 

1.22765 

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43.8 

1.19358 

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1 .06669 

44.6 

1.21588 

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1.05790 

11 


y = 

= 0. 16 

r = 

0.17 

9 

X 

Y 

T 

9 

X 

l 

Y 

T 

0 

52.0 

2.20019 

1.77260 

1.62859 

0 

51.0 

2.13564 

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I - 57577 

51.8 

2.13736 

1.69247 

I . 60460 

50.8 

2.07535 

1-58739 

I - 55277 

51.6 

2.08241 

1.62287 

1.58225 

50.6 

2.02246 

1.52276 

I -53132 

51-4 

2.03328 

1. 56111 

1.56122 

50.4 

1.97508 

1.46529 

I.5IIII 

51.2 

1.98869 

1.50545 

I. 54127 

50.2 

I. 93201 

I. 41340 

1.49191 

51.0 

1.94773 

1.45469 

1.52223 

50.0 

I . 89240 

1.36603 

I -47358 

50.8 

1.90978 

1 . 40798 

1.50398 

49.8 

1.85566 

1.32239 

1.45600 

50.6 

1-87434 

1.36468 

I . 48642 

49.6 

1.82133 

1.28191 

1.43908 

50.4 

1.84107 

I. 32431 

1.46947 

49-4 

I . 78907 

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1.42274 

50.2 

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1.45308 

49-2 

1.75860 

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50.0 

1.77989 

1.25088 

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49.0 

I. 72971 

1.17536 

1-39159 

49-8 

1.75158 

I. 21725 

1.42176 

48.8 

1.70222 

1.14385 

1.37668 

49-6 

1.72456 

1-18539 

1.40674 

48.6 

1-67597 

1-11397 

1.36218 

49‘4 

1.69871 

1-15512 

1.39211 

48.4 

1.65085 

1-08557 

1.34805 

49-2 

1.67391 

I . 12629 

1.37785 

48.2 

1.62674 

1.05852 

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49-0 

1.65007 

1.09878 

1.36392 

48.0 

1.60356 

1.03268 

I . 32079 

48.8 

1.62712 

1.07246 

I . 35030 

47-8 

1.58123 

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1.30762 

48.6 

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1.04725 

1.33698 

47-6 

1.55968 

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1.29473 

48.4 

1.58356 

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1.54278 

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46.8 

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1.43367 

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1 1.39282 

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46.6 

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1 1.36086 

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1.38508 

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1-34543 

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1.17419 

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1.33968 

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44-6 

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1.31097 

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1.27311 

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44.6 

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1.07900 

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1-09559 

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1.20758 

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1.06064 

44.0 

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I .08632 

43-0 

1.19518 

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1.05163 

43-8 

1.21872 

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42.8 

1.18299 

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43-6 

I . 20646 

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42.6 

I . 171OO 

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1.03392 

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43-2 

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I . 14760 

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1 1.170S2 

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1-04137 

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I .ooSii 

42.8 

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1.03292 

1 41 -8 

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42.6 

j 1.1479S 

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1.02437 

j 41  -6 

1.113S7 

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12 


y 

= 0.18 

y = 

0. 19 

X 

Y 

T 

1 ^ 

X 

Y 

T 

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50.0 

2.06533 

1-54956 

I . 52292 

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49.8 

2 . 00860 

I .48218 

I. 50107 

48.8 

1-93855 

1-37858 

1-44975 

49.6 

1-95852 

I. 42312 

1.48063 

48.6 

1.89175 

1-32530 

1.4303S 

49.4 

1.91346 

1.37036 

1.46132 

48.4 

1.84937 

1.27740 

I .41203 

49.2 

1-87235 

1.32256 

1.44295 

48.2 

1.81053 

1.23380 

1-39452 

49.0 

1-83445 

1.27881 

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I. 7992 I 

1.23841 

1.40851 

47.8 

I . 74107 

1.15665 

1.36162 

48.6 

1.76624 

1.20087 

1.39226 

47-6 

I . 70963 

I . 12209 

1.34605 

48.4 

1.73520 

1.16579 

1.37655 

47-4 

1.67997 

I .08972 

I • 33099 

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1.705S6 

1.13285 

1-36134 

47-2 

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1.05928 

1.31639 

48.0 

1.67800 

1.10181 

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47.0 

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1-03053 

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1.65146 

1.07244 

I. 33221 

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1 1-59969 

1.00330 

I . 28840 

47.6 

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1-04457 

1.31824 

46.6 

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1-27495 

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1.60182 

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1.30461 

46.4 

1-55194 

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1.26183 

47.2 

1-57850 

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1.52948 

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1.55606 

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1.27830 

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46.4 

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1.44730 

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46.2 

1-47379 

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1.42839 

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45.8 

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1.39223 

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1.41852 

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17.4 

.47224 

.085752 

•38095 

15.4 

. 41009 

.065125 

•33307 

17.2 

.46199 

■.082559 

.37468 

15.2 

.40045 

.062488 

.32706 

17.0 

.45205 

.079501 

.36852 

15.0 

.39111 

•059967 

.32114 

16.8 

.44240 

.076569 

.36246 

14. 8 

.38204 

.057554 

•31532 

16.6 

.43302 

.073754 

•35648 

14.6 

•37323 

.055242 

.30958 

16.4 

.42389 

.071050 

.35060 

14.4 

. 36465 

.053024 

•30393 

16.2 

.41499 

.068450 

.34479 

14.2 

•35630 

.030894 

.29836 

16.0 

.40632 

.065947 

. 33906 

14.0 

•34815 

.048848 

.29286 

15.8 

. 397S6 

.063537 

•33341 

13.8 

.34020 

.046881 

•28743 

15-6 

.38960 

.061213 

•32783 

13.6 

•33244 

. 044989 

. 28208 

15-4 

.38152 

.058972 

.32232 

13.4 

•32485 

.043167 

.27678 

15.2 

.37361 

.056810 

.31688 

13.2 

•31743 

.041412 

•27155 

15-0 

.36587 

.054722 

•31149 

13.0 

.31016 

.039721 

.26638 

14.8 

.35829 

.052705 

.30617 

12.8 

•30305 

.038091 

.26127 

14.6 

.35087 

.050756 

.30091 

12.6 

.29607 

.036518 

.25621 

14.4 

.34358 

.048872 

.29570 

12.4 

.28923 

.035001 

.25120 

14.2 

.33643 

.047050 

.29054 

12.2 

.28251 

•033537 

.24625 

14.0 

.32942 

.045287 

.28544 

12.0 

•27592 

.032124 

.24134 

13.8 

.32252 

.043581 

.28039 

II. 8 

. 26945 

.030760 

. 23648 

13.6 

.31575 

.041929 

•27538 

II  .6 

.26308 

.029442 

.23167 

13-4 

.30909 

.040330 

.27042 

II. 4 

.25683 

.028170 

.22690 

13-2 

.30254 

.038782 

.26551 

II  .2 

.25068 

.026940 

. 22218 

13.0 

.29609 

.037282 

. 26064 

II. 0 

.24462 

.025753 

.21749 

12.8 

.2S974 

.035829 

.25581 

10.8 

.23866 

.024606 

.21285 

12,6 

.28349 

.034421 

.25102 

10.6 

.23279 

•023497 

.20825 

12.4 

.27734 

.033057 

.24627 

10.4 

.22701 

.022426 

. 2036S 

12.2 

.27128 

.031735 

.24156 

10.2 

.22132 

.021391 

.19914 

12.0 

.26531 

.030454 

.23690 

10. 0 

.21571 

.020391 

. 19464 

II. 8 

.25942 

.029213 

.23227 

9.8 

.21018 

.019425 

. 1901S 

II. 6 

.25361 

.028010 

.22767 

9.6 

.20472 

.018492 

•18575 

II. 4 

.24788 

.026844 

. 22310 

9-4 

. 19934 

.017591 

•18135 

II. 2 

. 24222 

.025713 

.21856 

9.2 

• 19403 

.016721 

.17699 

17 


= 1.0 


7=1.1 


X 

Y 

T 

X 

Y 

T 

u 

17.0 

•59414 

. 116140 

.41265 

0 

15.4 

.51899 

.090241 

•36756 

16.8 

•56934 

. 108606 

•40293 

15-2 

.49780 

•084445 

.35864 

16.6 

•54752 

. 102059 

.39382 

15-0 

.47885 

•079331 

.35022 

16,4 

•52792 

.096251 

•38519 

14.8 

.46163 

.074748 

•34219 

16.2 

.51004 

.091024 

•37696 

14.6 

•44578 

.070591 

•33451 

16.0 

•49357 

.086268 

.36907 

14.4 

.43108 

.066788 

.32711 

15-8 

.47824 

.081903 

•36147 

14.2 

•41732 

.063282 

•31996 

15-6 

.46389 

.077869 

.35412 

14.0 

.40438 

.060032 

.31302 

15-4 

•45037 

.074119 

• 34699 

13.8 

•39215 

.057004 

. 30629 

15.2 

•43758 

.070618 

.34006 

13.6 

•38053 

•054171 

•29974 

15.0 

42541 

.067336 

•33331 

13-4 

•36945 

.051512 

•29334 

14.8 

.41381 

.064249 

.32672 

13.2 

.35886 

.049008 

.28709 

14.6 

.40271 

.061337 

.32029 

13.0 

•34871 

.046645 

.28098 

14.4 

.39206 

.058582 

•31399 

12.8 

•33895 

.044409 

•27499 

14.2 

.38182 

•055972 

.30782 

12.6 

•32954 

.042291 

.26912 

14.0 

•37195 

•653493 

•30177 

12.4 

.32047 

.040279 

.26336 

13-8 

.36242 

•051134 

.29583 

12.2 

.31169 

.038366 

•25769 

13.6 

•35320 

.048887 

.28999 

12.0 

.30320 

•036544 

.25212 

13.4 

•34427 

•046744 

.28425 

II. 8 

. 29496 

.034807 

. 24664 

13.2 

•33561 

. 044696 

.27860 

II. 6 

.28695 

.033150 

.24124 

13.0 

.32720 

.04273S 

•27303 

II. 4 

•27917 

•031567 

.23592 

12.8 

.31902 

. 040864 

•26755 

II. 2 

.27160 

.030053 

.23068 

12.6 

•31105 

. 039069 

.26214 

II  .0 

.26422 

.028605 

.22551 

12.4 

.30329 

•037348 

.25681 

10.8 

.25702 

.027219 

.22040 

12.2 

.29571 

.035696 

•25155 

10.6 

.24999 

.025891 

.21536 

12.0 

.28832 

.034111 

.24635 

10.4 

.24313 

.02461S 

.21039 

11.8 

. 28109 

.032588 

.24122  I 

10.2 

.23641 

.023398 

•20547 

II  .6 

.27403 

.031125 

•23615 

10. 0 

.22985 

.022228 

.20060 

II. 4 

.26711 

.029718 

•23113 

9.8 

.22341 

.021105* 

•19579 

II . 2 

.26034 

.028365 

.22618 

9.6 

.21711 

. 020028 

. 19103 

II  .0 

•25371 

.027063 

.22127 

9.4 

.21093 

.01S994 

.18632 

10.8 

.24720 

.025G11 

.21642 

9.2 

.20487 

.oiSooi 

. 1S166 

10.6 

. 240S2 

.024605 

.21162 

9.0 

. I9S92 

.017049 

.17704 

10.4 

•23456 

.023444 

. 206S6 

8.8 

. 19308 

.016134 

.17247 

10.2 

.22841 

.022326 

.20215 

8.6 

•18734 

•015255 

• 16794 

10. 0 

.22236 

.021249 

•19749 

8.4 

. 18170 

.014412 

.16346 

9.8 

.21642 

.020212 

. 192S6 

8.2 

.17615 

.013603 

.15901 

9.6 

.21058 

.019213 

.1SS2S 

8.0 

. 17069 

.012S26 

. 15460 

9.4 

.20483 

.01G252 

•1S374 

7.8 

.16532 

.012080 

.15023 

9.2 

. 19918 

.017325 

.17924 

7.6 

. 16003 

.011365 

•14589 

9.0 

.19361 

.016433 

•17477 

7.4 

.15482 

.0106S0 

.14159 

8.8 

.18812 

•015574 

.17034 

7.2 

• 14969 

.010022 

• 13733 

8.6 

. 18271 

•014747 

.16594 

7.0 

•14463 

.009392 

•13309 

8.4 

•17738 

.013951 

.16158 

6.8 

•13965 

.00^57^^ 

.12388 

8.2 

.17213 

.013185 

.15726 

6.6 

•13473 

.00S210 

.12471 

8.0 

. 16696 

.012447 

.15297 

6.4 

. I298S 

•007657 

.12057 

7.8 

.16185 

.011738 

.14871 

6.2 

.12509 

.007129 

.11646 

7.6 

.156S1 

.011056 

•14448 

6.0 

i .12037 

.006625 

.11233 

IS 


Y 

= 1.2 

y = 

= 1-3 

9 

X 

Y 

T 

9 

X 

Y 

1 T 

0 

14-6 

.52776 

.089263 

•35707 

0 

13.4 

.46665 

.071208 

. 32266 

14-4 

•49953 

.081960 

•34683 

13.2 

•44277 

.065561 

■31329 

14.2 

.47586 

.075927 

•33745 

13.0 

.42223 

.060781 

•30459 

14-0 

■45528 

•070755 

•32871 

12.8 

.40407 

.056621 

■ 29643 

13-8 

.43694 

.066215 

.32047 

12.6 

.38770 

.052932 

.28868 

13-6 

.42031 

.062161 

.31263 

12.4 

•37274 

.049614 

.28128 

13-4 

•40505 

.058497 

•30512 

12.2 

•35892 

. 046600 

.27417 

13-2 

.39091 

•055153 

.29790 

12.0 

.34604 

.043839 

.26731 

13.0 

•37770 

.052079 

•29093 

II. 8 

•33396 

.041294 

.26068 

12.8 

.36528 

.049236 

.28418 

II. 6 

.32258 

.038936 

•25424 

12.6 

•35355 

.046592 

.27762 

II. 4 

.31178 

.036740 

■24797 

12.4 

•34242 

.044125 

.27123 

II . 2 

.30152 

.034688 

.24187 

12,2 

.33182 

.041813 

.26501 

II  .0 

.29172 

.032765 

•23591 

12,0 

.32169 

.039641 

.25892 

10.8 

.28233 

.030958 

.23008 

II. 8 

.31198 

.037595 

.25297 

10.6 

•27333 

.029256 

.22458 

II. 6 

.30265 

.035663 

.24715 

10.4 

. 26466 

.027650 

.21878 

II. 4 

.29367 

.033835 

•24143 

10.2 

.25630 

.026131 

.21329 

II. 2 

.28500 

.032103 

.23582 

■ 10. 0 

.24823 

.024693 

.20790 

II. 0 

.27662 

.030459 

.23031 

9.8 

. 24041 

.023329 

. 2C200 

10.8 

.26851 

.028897 

.22489 

9-6  ! 

.23284 

.022034 

•19738 

10.6 

.26065 

.027411 

.21956 

9-4 

.22549 

.020804 

.19224 

10,4 

.25301 

.025995 

.21431 

9.2 

.21835 

.019635 

. 1S718 

10.2 

•24559 

. 024646 

.20913 

9.0 

.21141 

.018522 

. 1S220 

10. 0 

.23836 

.023359 

• 20403 

8.8 

. 20464 

.017462 

.17728 

9.8 

.23132 

.022130 

.19900 

8.6 

. 19804 

•016453 

.17242 

9.6 

.22446 

.020957 

• 19404 

8.4 

. 19160 

.015491 

.16763 

9-4 

.21776 

.019836 

.18913 

8.2 

•18532 

•014573 

. 16290 

9.2 

.21121 

.018764 

.18429 

8.0 

.17917 

.013699 

.15S22 

9.0 

.20481 

.017738 

•17950 

7.8 

.17316 

.012865 

•15359 

8.8 

•19855 

.016758 

•17477 

7.6 

.16728 

.012069 

. 14902 

8.6 

.19242 

.015819 

. 17009 

7-4 

.16151 

.011310 

.14449 

8.4 

. 18641 

.014922 

. 16546 

7.2 

.15586 

.010586 

. 14002 

8.2 

.18052 

.014062 

. 16088 

7.0 

.15032 

.009896 

•13558 

8.0 

•17474 

.013240 

•15635 

6.8 

• 14489 

.009238 

. I312O 

7.8 

. i6go8 

.012454 

.15186 

6.6 

•13955 

.008611 

.12685 

7.6 

•16351 

.011701 

• 14741 

6.4 

•13430 

.008013 

.12254 

7.4 

.15804 

.010981 

.14300 

6.2 

.12915 

.007444 

. 11828 

7.2 

.15267 

.010293 

.13864 

6.0 

. 12408 

. 006903 

.11405 

7.0 

•14738 

.009634 

•13431 

5.8 

.11910 

.006387 

.10985 

6.8 

.14218 

. 009005 

.13002 

5.6 

.11419 

.005898 

.10570 

6.6 

.13706 

. 008404 

.12576 

5-4 

• 10937 

•005433 

.10157 

6.4 

.13203 

.007830 

•12154 

5-2 

. 10461 

.004992 

.09748 

6.2 

.12706 

.007282 

•I1735 

5-0 

•09993 

.004574 

•09342 

6.0 

.12218 

.006760 

,11320 

4.8 

•09532 

.0041 78 

. 08939 

5.8 

.11736 

.006262 

. 10908 

4.6 

■09077 

.003S04 

08539 

5.6 

.11261 

.005788 

. 10499 

4.4 

.08628 

.003451 

.08142 

5.4 

• 10793 

•005337 

.10093 

4.2 

.0S1S5 

.003118 

.07748 

5.2 

.10331 

. 004908 

. 09689 

4.0 

.07748 

.002805 

•07357 

19 


y 

= 1.4 

r = 

1-5 

1 

^ 1 

Y 

T 

i 

Y 

T 

0 

12.2 

. 40049 

.054244 

.28670 

u 

II. 4 

•37183 

.046879 

. 26693 

12.0 

.38169 

.050213 

.27842 

II. 2 

•35357 

.043229 

•25879 

II. 8 

•36495 

.046685 

.27061 

II  .0 

•33734 

. 040046 

.25112 

II. 6 

• 34979 

•043544 

.26318 

10.8 

.32267 

.037220 

.24384 

II. 4 

•33588 

.040714 

.25607 

10.6 

.30923 

•034679 

.23687 

II. 2 

.32299 

.038138 

.24923  . 

10.4 

.29678 

•032373 

.23016 

II  .0 

•31095 

•035777 

. 24262 

10.2 

.28517 

.030263 

.22360 

10.8 

. 29964 

•033599 

.23623 

10. 0 

.27427 

.028320 

•21743 

10.6 

.28896 

.031580 

.23001 

9-8 

.26398 

.026524 

.21134 

10.4 

.27882 

.029701 

. 22396 

9.6 

•25421 

.024855 

.20542 

10.2 

.26917 

.027946 

.21806 

9-4 

.24492 

.023299 

• 19964 

lO.O 

•23994 

.026303 

.21230 

9.2 

.23604 

.021845 

. 194C0 

9.8 

.25110 

.024760 

. 20666 

9.0 

•22753 

.020482 

.18848 

9.6 

. 24260 

.023307 

.20113 

8.8 

.21936 

.019202 

. 18308 

9.4 

• 23442 

.021938 

•19572 

8.6 

•21149 

.017998 

• 17777 

9.2 

.22653 

. 020646 

. 19040 

8.4 

. 20390 

.016S64 

•17257 

9.0 

.21890 

.019424 

.18517 

8.2 

•19657 

•015794 

• 16746 

8.8 

.21152 

.018267 

. 18003 

8.0 

. 18946 

.014783 

. 16243 

8.6 

•20435 

.017171 

•17497 

7.8 

.18258 

.013S27 

•15748 

8.4 

.19740 

.016131 

. 16999 

7.6 

•17590 

.012924 

.15260 

8.2 

. 19064 

•015145 

. 16508 

7-4 

. 16940 

.012068 

. 147S0 

8.0 

. 18405 

.014209 

. 16024 

7.2 

. 16308 

.OII25S 

.14306 

7-S 

.17764 

.013319 

•15546 

7.0 

•15692 

.010491 

• 131*39 

7.6 

•17139 

•012474 

.15075 

6.8 

.15091 

.009764 

•1337S 

7-4 

. 16529 

.011670 

. 14610 

6.6 

• 14505 

.009075 

. 12922 

7.2 

•15933 

.010906 

.14150 

6.4 

•13932 

.008422 

. 12472 

7.0 

•15350 

.010180 

•13695 

6.2 

•13372 

. C07S03 

. 1202S 

6.8 

•14779 

.009489 

.13246 

6.0 

.12824 

.007218 

. 115SS 

6.6 

. 14221 

.008S33 

.12801 

5.8 

.12288 

.006663 

•11153 

6.4 

•13673 

.00S209 

. 12361 

5.6 

I .11762 

.006139 

.10722 

6.2 

•13137 

.007617 

.11926 

5-4 

.11247 

.005642 

. 10296 

6.0 

. 12610 

.007054 

.11495 

5-2 

. 10741 

•005173 

.09S74 

5.8 

. 12094 

.006520 

. 1106S 

5-0 

.10245 

.004731 

•09457 

5.6 

.11586 

.006014 

• 10643 

4.8 

•09758 

.004313 

.09043 

5.4 

.11088 

•005534 

. 10226 

4.6 

•09279 

.003919 

.0S633 

5-2 

.10598 

.005080 

.09810 

4-4 

.08809 

.003549 

.08226 

5-0 

. 10116 

.004650 

.09399 

4.2 

•0S347 

.003201 

.07S23 

4.8 

.09642 

.004244 

.0S990 

4.0 

.07S91 

.002875 

.07423 

4.6 

.09176 

.003860 

.0S5S5 

3.8 

•07443 

.002569 

.07027 

4-4 

08716 

•003499 

.08184 

3-6 

.07002 

.0022S4 

.06634 

4.2 

.08264 

.00315S 

•077S5 

3-4 

.06568 

.002018 

.06244 

4.0 

.07818 

.002S39 

.07390 

3-2 

.06139 

.001771 

.05856 

3.8 

•07379 

•002539 

.06997 

3-0 

.05717 

.001543 

.05472 

3-6 

.06946 

.002259 

. 06607 

2.8 

.05301 

.001332 

.05090 

3-4 

.06519 

.001998 

.06220 

2.6 

1 .04891 

.00113S 

.04711 

3-2 

.06098 

•001755 

.05836 

2.4 

•04487 

.000961 

• 04335 

3-0 

.05681 

.001530 

•05455 

2.2 

.04088 

.oooSoi 

.03962 

2.8 

.05270 

.001322 

.05076 

2.0 

.03693 

.000657 

•03591 

20 


Y 

= 1.6 

r = 

1.7 

9 

X 

Y 

T 

X 

Y 

T 

0 

10.8 

.042866 

.23411 

0 

10.2 

•33774 

.038251 

•23987 

10.6 

.33811 

.039244 

•24577 

ro.o 

.31860 

.034841 

•23157 

10-4 

.32135 

.036137 

•23799 

9.8 

.30198 

•031938 

•22384 

10.2 

.30635 

•033411 

.23064 

g.6 

.28718 

.029407 

.21655 

10. 0 

.29272 

.030982 

.22363 

9.4 

• 27377 

.027162 

.20961 

9.8 

.2S018 

.028793 

.21691 

9.2 

.26146 

•025147 

.20297 

9.6 

.26853 

.026803 

.21045 

9.0 

.25006 

.023321 

.19658 

9-4 

.25764 

.024980 

.20419 

8.8 

.23942 

.021653 

. I904I 

9.2 

.24740 

.023302 

.19813 

8.6 

,22941 

.020122 

• 18444 

9.0 

.23770 

.021749 

. 19224 

8.4 

.21996 

.018710 

.17863 

8.8 

.22850 

,020307 

. 18650 

8.2 

.21099 

.017401 

.17297 

8.6 

.21972 

.018964 

. 18091 

8.0 

. 20245 

.016185 

. 16746 

8.4 

.21133 

.017709 

•17543 

7.8 

• 19429 

.015052 

' . 16207 

8.2 

.20328 

•016535 

. 1700S 

7.6 

. 18646 

.013994 

.15679 

8.0 

.19554 

•015433 

. 16483 

7-4 

.17894 

.013004 

.15163 

7.8 

. 1880S 

.014398 

.15968 

7.2 

.17170 

.012077 

. 14656 

7.6 

. 18088 

.013425 

.15462 

7.0 

.16472 

.011206 

.14158 

7-4 

.17392 

.012509 

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6.8 

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.010389 

.I3C69 

7.2 

.16718 

.011645 

•14473 

6.6 

- 1 5 142 

.009621 

.13188 

7.0 

. 16064 

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•13994 

6.4 

. 14503 

.008898 

.12715 

6.8 

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•13519 

6.2 

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6.6 

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6.0 

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.007578 

.11788 

6.4 

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5.8 

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6.2  1 

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5-6 

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. 006409 

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6.0 

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5-4 

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. i04-;6 

5.8 

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5-2 

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5-6 

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4.6 

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4-4 

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4.8 

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4.2 

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4.6 

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4.0 

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4.4 

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3.8 

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4.2 

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3-6 

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3.8 

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3.6 

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3-0 

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3.4 

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2.8 

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3.2 

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2.6 

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3.0 

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2.4 

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2.8 

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2.2 

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2.6 

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2.0 

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2.4 

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1.8 

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2.2 

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1.6 

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2.0 

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r.4 

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1.8 

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r.2 

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1.6 

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I.O 

.01800 

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1.4 

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0.8 

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.000101 

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21 


r 

= 1.8 

y- 

1.9 

9 

X 

Y 

T 

9 

X 

Y 

T 

0 

9-6 

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.22453 

0 

9.0 

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.20836 

9-4 

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8.8 

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. 20065 

g.2 

.27994 

.027634 

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8.6 

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• 19342 

9-0 

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.025369 

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8.4 

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8.8 

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.023361 

•19503 

8.2 

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8.6 

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.18854 

8.0 

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.018142 

•17377 

8.4 

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.019926 

.18230 

7.8 

. 20969 

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•16773 

8.2 

.22008 

.018437 

.17627 

7.6 

. 20007 

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8.0 

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.017071 

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7-4 

. 19100 

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.15620 

7.8 

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.015813 

• 16474 

7.2 

. 18242 

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.15068 

7.6 

. 19281 

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7.0 

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7-4 

. 18460 

.013569 

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6.8 

. 16647 

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. 14005 

7.2 

. 17676 

.012564 

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6.6 

. 15902 

.010287 

• 13492 

7.0 

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• 14338 

6.4 

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.12989 

6.8 

. 16202 

.010754 

.13832 

6.2 

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. 12496 

6.6 

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6.0 

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. I20I2 

6.4 

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.009171 

. 12848 

5.8 

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6.2 

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5-6 

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6.0 

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.007781 

.11897 

5-4 

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.006144 

. io6og 

5-8 

. 12946 

.007151 

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5-2 

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.003603 

.10157 

5-6 

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.006559 

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5-0 

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5-4 

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' 4.8 

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5-2 

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. 10082 

4.6 

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5.0 

. 10670 

.004997 

.09643 

4.4 

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.003773 

.08408 

4.8 

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.004540 

.09210 

4.2 

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.003389 

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4.6 

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.004112 

.08783 

4.0 

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.003032 

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4.4 

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.003712 

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3-8 

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4.2 

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.003338 

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3-6 

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4.0 

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.002989 

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3-4 

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.002106 

.06340 

3-8 

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3-2 

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3-6 

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3-0 

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3-4 

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2.8 

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3-2 

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2.6 

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.001174 

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3-0 

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.001585 

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2.4 

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2.2 

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• .03997 

2.6 

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2.0 

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2.4 

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.04368 

1.8 

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2.2 

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.000816 

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1.6 

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.000421 

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2.0 

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1.4 

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.000319 

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1.8 

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1.2 

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1.6 

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I.O 

.01S07 

.000160 

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1.4 

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0.8 

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.000102 

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1 . 2 

.02179 

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0.6 

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I.O 

.01803 

.000159 

.01774 

0.4 

. 00708 

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0.8 

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.000101 

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+ .2 

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.000006 

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0.6 

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.01058 

0.0 

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0.4 

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. 000024 

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1 .000006 

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0.2 

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.000006 

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0.4 

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j .000024 

I .00694 

I 

22 


y 

= 2.0 

y = 

= 2.  I 

X 

Y 

T 

X 

Y 

T 

0 

8.6 

.27661 

.026059 

. 19960 

0 

8.2 

1 

; .26354 

.023632 

. 19013 

8.4 

.25962 

.023518 

.19182 

8.0 

I . 24666 

.021250 

.18243 

8.2 

.24482 

.021358 

•18455 

7.8 

; .23203 

.019219 

.17522 

8.0 

.23162 

.019478 

.17769 

7.6 

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. 16842 

7.8 

.21964 

.017816 

.17117 

7-4 

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.015908 

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7.6 

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. 16491 

7.2 

. 19644 

j .014525 

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7-4 

. 19843 

.014985 

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7.0 

. 18644 

1 .013279 

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7.2 

. 18S90 

.013763 

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6.8 

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1 .012149 

. 14406 

7.0 

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.012646 

• 14744 

6.6 

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6.8 

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6.4 

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6.6 

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6^2 

i .15220 

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6.4 

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6.0 

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6.2 

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5.8 

: .13736 

.007769 

.11764 

6.0 

. 14140 

.008242 

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5-6 

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.007085 

.11273 

5-8 

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.007544 

.11647 

5-4 

j .12412 

.006451 

.10791 

5-6 

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5-2 

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5-4 

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5-2 

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4.8 

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5-0 

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4.6 

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4.8 

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4.4 

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4.6 

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4.2 

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4-4 

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4.0 

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4.2 

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3-8 

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4.0 

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3-6 

1 

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3.8 

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3.4 

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3.6 

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3-2 

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3-4 

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3-0 

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3.2 

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2.8 

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3.0 

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2.6 

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2.8 

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2.4 

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2.6 

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2.2 

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2.4 

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2.0 

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2.2 

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1.8 

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2.0 

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1.6 

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1.8 

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1.4 

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1.6 

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1.2 

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1.4 

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1 .0 

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1.2 

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0.8 

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0,6 

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0.8 

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0.4 

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0.6 

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+ .2 

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0.4 

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0.8 

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0.6 

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I.O 

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0.8 

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1.2 

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23 


y 

= 2.2 

y = 

2.3 

X 

Y 

T 

X 

Y 

T 

0 

8.0 

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0 : 
7-6  j 

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7-4 

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7.6 

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7.2 

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7-4 

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7.0 

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7.2 

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6.8 

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7.0 

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6.6 

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6.8 

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6.4 

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6.6 

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6.4 

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6.0 

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6.2 

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. 12940 

5-8 

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6.0 

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5.6 

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5-8 

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5-4 

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5-6 

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5-2 

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5-4 

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5-2 

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4.8 

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4.6 

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4.8 

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4.6 

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4.2 

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4.4 

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4.0 

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4.0 

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3-8 

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3-2 

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3-4 

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3-0 

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3-2 

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2.8 

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2.6 

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2.8 

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1.8 

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1.6 

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1.4 

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1.6 

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0.8 

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0.6 

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r 

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y = 

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7-4 

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0 

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3.8  I 

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3-4 

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3.C 

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r.4 

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1.6 

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2.0 

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2.4 

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25 


r 

= 2.6 

r = 

2.7 

^ i 

X i 

Y 

T 

. 

(p  i 

X 

Y i 

T 

u 

6.6 

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1.8 

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2.2 

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2.4 

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2.6 

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2.6 

1 .04092 

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2.8 

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2.8 

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3.0 

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26 


i 

i 


i 


y 

— 2.8 

y = 

r 2.9 

f 

X 

Y 

T 

9 

X 

Y 

T 

0 

6.2 

.19970 

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i ^ 

I 

.19388 

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6.0 

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5.8 

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5.8 

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5-6 

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5-6 

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5-4 

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5.2 

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5-2 

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5-0 

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5-0 

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4.8 

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4.8 

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4.6 

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4.6 

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4.4 

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4-4 

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4.2 

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4-0 

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4.0 

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3.8 

j .08618 

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3-8 

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3-6 

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3-6 

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3-2 

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3-2 

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3-0 

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2.2 

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2.0 

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1.8 

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1.6 

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1.4 

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1-4. 

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1.2 

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1.2 

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I.O 

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I.O 

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0.8 

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0.8 

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0.6 

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0.4 

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0.4 

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1.2 

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1.6 

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3-0 

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3-2 

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3-2 

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3-4 

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27 


y 

= 3-0 

y = 

3-1 

^ 1 

Y 

T 

9 

X 

Y 

T 

(J 

5.6 

. 17062 

.010218 

.12684 

0 

5.6 

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5-4 

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5-4 

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5.2 

. 14506 

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5^2 

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5-0 

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5-0 

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4.8  [ 

.12510 

. 006050 

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4.8 

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4.6 

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4.6 

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4-4 

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4-4 

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4.2 

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4.2 

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4.0 

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4.0 

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3-8 

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3-8 

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3-6 

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3-6 

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3-4 

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3.4  ' 

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3-2 

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3.2 

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3-0 

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3-0 

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2.8 

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2.8 

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2.6 

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2.6  j 

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2.4 

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2.4 

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2.2 

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2,2 

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2.0 

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2.0 

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1.8 

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1.8 

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1 .0 

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0.8 

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1.2 

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1.6 

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2.2 

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2.2 

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2.4 

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2.4 

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2.6 

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2.6 

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2.8 

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2.8 

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3-0 

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3-0 

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3-2 

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3-2 

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3-4 

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3-4 

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3-6 

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3-6 

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3-8 

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3.8 

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28 


y 

= 3-2 

r = 

3-3 

9 \ 

X 

Y 

T 

9 i 

X 

Y 

T 

u 

5-2 

.15612 

.008631 

.11704 

U 

5-2 

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5-0 

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5-0 

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4.8 

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4.8 

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4.6 

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4.6 

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4.4 

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4-4 

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4.2 

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4.2 

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4.0 

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4.0 

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3-8 

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3-8 

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3-6 

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3-6 

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3-4 

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3-4 

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3-2 

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3-2 

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3-0 

. 06400 

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3-0 

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2.8 

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2.8 

. 06002 

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2.6 

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.04959 

2.6 

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.04976 

2.4 

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2.4 

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2.2 

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.04128 

2.2 

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2.0 

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2.0 

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1.8 

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1.8 

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1.6 

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. 000446 

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1.6 

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. 000448 

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1-4 

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1.4 

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1.2 

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1.2 

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1 .0 

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0.8 

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0.8 

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0.6 

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0.6 

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0.4 

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0.4 

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+ •2 

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0.4 

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0.4 

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0.6 

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0.6 

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0.8 

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■ .000092 

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I.O 

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1.2 

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1.4 

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1.6 

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1.6 

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• .02999 

2.0 

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2.0 

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2.2 

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2.2 

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2.4 

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2.4 

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. 000749 

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2.6 

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2.6 

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2.8 

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2.8 

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3-0 

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3-0 

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. 04869 

3-2 

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3-2 

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3-4 

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3-4 

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3-6 

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3-6 

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3-8 

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3.8 

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4.0 

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4-0 

.05808 

.001912 

.06365 

4.2 

.06082 

.002102 

.06675 

4-2 

.06053 

.002088 

.06658 

29 


y 

= 3-4 

y = 

3-5 

X 

Y 

T 

i X 

'Y 

T 

u 

5-0 

•15467 

.008315 

.11392 

u 

4.8 

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.007473 

.10854 

4.8 

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. 10685 

4.6 

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.006369 

. 10167 

4.6 

. 12845 

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4-4 

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4.4 

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4.2 

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4.2 

. 10869 

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4.0 

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4.0 

. 10023 

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3.8 

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3-8 

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3-6 

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3-6 

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3-4 

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3-4 

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3-2 

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3-2 

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3-0 

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3-0 

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2.8 

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2.8 

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2.6 

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2.6 

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2.4 

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2.4 

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2.2 

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2.2 

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2.0 

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2.0 

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1.8 

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1.8 

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1.6 

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1.6 

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1.4 

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1.4 

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1 . 2 

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1 . 2 

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I.O 

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1 .0 

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0.8 

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0.8 

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0.6 

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0.6 

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0.4 

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0.4 

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3-2 

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3-4 

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3-4 

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3.6 

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4.0 

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4.2 

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4-4 

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4.4 

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4.6 

j . 06469 

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30 


r = I r = 3-7 


f 

X 

Y 

T 

<P 

X 

Y 

T 

0 

4.6 

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u 

4.6 

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4-4 

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2.6 

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2.2 

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2.0 

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1.8 

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4.8 

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4-8 

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31 


7 

= 3.8 

j 

7 = 

3-9 

X 

Y 

ip  !i 

X I 

Y 

m 

± 

0 

4-4 

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0 1 
4-4 

1 

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4.2  ; 

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3.8  j 

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3-6 

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3-4 

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3-4  1 

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4.0 

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4.4 

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4.6 

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4.6 

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4.8 

1 .06600 

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4.8 

1 .06569 

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5-0 

■ .06824 

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5-0 

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32 


y 

= 4-0 

y = 

4-1 

X 

Y 

T 

X 

Y 

T 

0 

4.2 

.12735 

.005704 

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0 

4.2 

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4.0 

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4.0 

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3-8 

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. 004008 

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3.8 

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3-6 

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3-6 

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3-4 

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3-4 

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3-2 

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3-2 

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3-0 

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3-0 

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2.8 

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2.8 

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2.6 

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2.6 

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2.4 

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2.4 

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2.2 

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. ;422i 

2.2 

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2.0 

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2.0 

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1.8 

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1.8 

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1.6 

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1.6 

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1.4 

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1-4 

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1.2 

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1.2 

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1,0 

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I.O 

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0.8 

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0.8 

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0.6 

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0.6 

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0.4 

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0.4 

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0.6 

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.000052 

.01026 

0.8 

.01325 

.000091 

.01360 

0.8 

.01324 

.000091 

.01360 

I.O 

.01636 

.000140 

.01690 

I.O 

.01634 

.000139 

.01689 

1.2 

.01941 

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.02016 

T.2 

•01937 

.000198 

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1.4 

.02238 

. 000266 

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1.4 

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.000265 

.02336 

1.6 

.02529 

.000342 

.02657 

1.6 

.02523 

.000341 

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1.8 

.02814 

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1.8 

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2.0 

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.03284 

2.0 

.03085 

. 0005 I 7 

.03281 

2.2 

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. 000620 

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2.2 

•03358 

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2.4 

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.000728 

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2.4 

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2.6 

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.000843 

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2.6 

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.000839 

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2.8 

.04160 

.000965 

.04506 

2.8 

.04146 

.000961 

•04499 

3-0 

•04415 

.001094 

.04805 

3-0 

.04399 

.001089 

•04797 

3-2 

. 04666 

.001229 

.05101 

3-2 

.04649 

.001224 

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3.4 

.04913 

.001371 

•05395 

3-4 

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3-6 

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3-6 

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,001512 

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3.8 

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.001675 

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3-8 

.05372 

.001666 

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4.0 

.05629 

.001836 

.06263 

4.0 

.05605 

.001825 

.06250 

4.2 

.05860 

.002002 

.06548 

4.2 

.05835 

.001990 

•06534 

4.4 

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.002174 

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4.4 

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.002160 

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4.6 

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.002351 

.07112 

4.6 

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.002336 

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4.8 

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.07392 

4.8 

.06506 

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5-0 

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5-0 

.06723 

.002704 

.07651 

5-2 

.06973 

.002915 

.07946 

52 

.06938 

.002896 

.07926 

33 


/ 


y 

= 4-2 

4-3 

f 

X 

Y 

T 

f 

X 

Y 

T 

0 

4.0 

. 12122 

.005169 

,09032 

0 

4.0 

. 12561 

.005431 

.09165 

3-8 

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.004276 

•08355 

3.8 

. IIT03 

•004435 

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3-6 

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•003573 

.07738 

3-6 

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.003677 

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3-4 

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.002998 

.07165 

3-4 

.08938 

.003069 

.07220 

3-2 

.07953 

.002517 

.06624 

3-2 

.08067 

.002566 

.06667 

3-0 

.07199 

.002109 

.06110 

3-0 

.07286 

.002143  1 

.06144 

2.8 

.06509 

.001759 

.05619 

2.8 

•06575 

.001783 

.05646 

2.6 

.05870 

.001457 

.05146 

2.6 

.05921 

.001474 

.05167 

2.4 

•05273 

.001197 

.04689 

2.4 

.05312 

.001209 

. 04706 

2.2 

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2.2 

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.000980 

.04260 

2.0 

.04185 

.000778 

.03817 

2.0 

.04207 

.000783 

.03827 

1.8 

.03683 

.000611 

.03398 

1.8 

.03700 

.000615 

.03406 

1.6 

.03205 

. 000469 

.02990 

1.6 

.03218 

-.000472 

. 02996 

1.4 

.02749 

.000350 

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1-4  ' 

.02758 

.000351 

.02595 

1,2 

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1.2  1 

.02318 

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1,0 

.01892 

.000170 

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I.O 

.01896 

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0.8 

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0.8 

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.000106 

.01442 

0.6 

.01097 

.000059 

.01072 

0.6 

.01098 

.000059 

.01072 

0.4 

.00720 

.000026 

.00709 

0.4 

.00720 

.000025 

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+.2 

•00354 

.000006 

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+ .2 

•00354 

.000006 

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0.0 

. 00000 

. 000000 

. 00000 

0.0 

.00000 

.000000 

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— .2 

.00344 

.000006 

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— .2 

•00344 

.000006 

•00347 

0.4 

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. 000024 

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0.4 

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.000023 

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0.6 

.01004 

.000052 

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0.6 

.01004 

.000052 

.01025 

0.8 

.01322 

.000091 

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0.8 

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.000090 

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1 .0 

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I.O 

.01629 

.000139 

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1.2 

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1.2 

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1-4 

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1.4 

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.000263 

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1.6 

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1.6 

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1.8 

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1.8 

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02961 

2.0 

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2.0 

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2.2 

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2.2 

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2.4 

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2.4 

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2.6 

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2.6 

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2.8 

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2.8 

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3-0 

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3-0 

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3-2 

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3-2 

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3-4 

.04874 

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3-4 

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3-6 

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3-6 

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3.8 

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3-8 

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4.0 

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4.0 

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4.2 

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4.2 

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4.4 

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4-4 

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4.6 

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4.6 

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4.8 

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4.8 

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5.0 

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5.0 

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5.2 

. 06904 

.002877 

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5-2 

1 . o6S6g 

.002S59 

.07SS5 

5-4 

.07114 

.003072 

.0S17S 

1 5-4 

i .07077 

.003052 

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3i 


• 

y 

= 4-4 

r = 

= 4.5 

9 

X 

Y 

T 

9 

X 

Y 

T 

0 

3-8 

.11434 

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0 

3.8 

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3-6 

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3-6 

. 10409 

.003923 

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3-4 

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.003147 

.07278 

3-4 

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3-2 

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.002620 

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3-2 

.08317 

.002676 

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3-0 

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3-0 

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2.8 

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2.8 

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2.6 

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2.6 

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.05212 

2-4 

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2.4 

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.001234 

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2.2 

.04775 

.000989 

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2,2 

.04807 

. 000998 

.04287 

2.0 

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2.0 

•04255 

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.03848 

1.8 

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1.8 

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.000623 

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1.6 

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1.6 

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1-4 

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1.4 

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1.2 

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1.2 

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I.O 

.01900 

.000171 

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I.O 

.01904 

.000171 

.01823 

0.8 

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0.8 

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0.6 

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0.6 

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.000059 

.01074 

0.4 

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0.4 

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+ ■2 

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0.0 

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0.0 

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0.4 

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0.4 

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0.6 

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0.6 

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0.8 

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0.8 

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I.O 

.01626 

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I.O 

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1.2 

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1.2 

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1.4 

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1.4 

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1.6 

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.02645 

1.6 

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1.8 

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1.8 

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2.0 

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2.0 

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2.2 

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2.2 

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2.4 

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2.4 

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2.6 

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2.6 

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2.8 

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2.8 

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3-0 

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3-0 

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3-2 

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3-2 

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3-4 

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•05353 

3-4 

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3-6 

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3-6 

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3.8 

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3.8 

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4.0 

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4.0 

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4.2 

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4.2 

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4-4 

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4-4 

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4.6 

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4.6 

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.002281 

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4.8 

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4.8 

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5.0 

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5-0 

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5.2 

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5-2 

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5.4 

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5-4 

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.003014 

.08114 

5.6 

1 .07247 

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. 0S402 

5-6 

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.003208 

.08381 

35 


y 

= 4.6 

r = 

4.7 

9 

X 

Y 

T 

X 

Y 

T 

0 

3-8 

. 12268 

.005092 

.08803 

0 

3-6 

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. 004240 

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3-6 

. 10690 

. 004070 

. 08060 

3-4 

.09679 

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3-4 

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3-2 

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3-2 

.08454 

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3-0 

.07682 

.002304 

.06295 

3-0 

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.002260 

.06255 

2.8 

.06873 

.001894 

•05763 

2.8 

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.001864 

.05732 

2.6 

.06146 

.001551 

*05258 

2.6 

.06087 

.001531 

•05235 

2.4 

•05483 

.001262 

•04777 

2.4 

•05439 

.001248 

•04759 

2.2 

.04872 

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2.2 

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2.0 

•04304 

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2.0 

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1.8 

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1.8 

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1.6 

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1.6 

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1.4 

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1-4 

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1.2 

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1.2 

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I.O 

.01912 

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I.O 

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0.8 

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0.8 

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0.6' 

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0.6 

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0.4 

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+ .2 

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0.0 

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1.2 

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1.4 

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1.6 

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2.6 

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2.8 

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2.8 

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3-0 

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3-0 

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3-2 

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3-2 

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3.4 

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3-4 

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3-6 

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3-8 

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3-8 

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4.0 

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4.6 

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4.6 

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4.8 

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4.8 

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5-0 

1 .06534 

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5-2 

, .06738 

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5-2 

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5.4 

' .06939 

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5-4 

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5-6 

; .0713S 

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*0833^ 

5-6 

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.003185 

•0S359  / 

5-8 

! .07334 

1 

.003362 

.08601 

36 


y 

= 4.8 

y ^ 

4-9 

9 

X 

Y 

T 

9 

X 

Y 

T 

0 

3-6 

.11380 

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.08269 

0 

3.6 

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. 004679 

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3-4 

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.003539 

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3.4 

. 10171 

.003667 

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3-2 

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3-2 

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3-0 

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3-0 

•07915 

. 002400 

.06380 

2.8 

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2.8 

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2.6 

.06207 

.001572 

.05282 

2.6 

.06272 

.001595 

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2.4 

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2.4 

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2.2 

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2.2 

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2.0 

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2.0 

.04356 

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1.8 

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1.8 

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.000640 

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1,6 

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.000485 

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1.6 

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1.4 

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1.4 

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1.2 

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1.2 

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I.O 

.01916 

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I.O 

.01921 

.000173 

.01831 

0.8 

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.000108 

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0.8 

.01505 

.000108 

.01449 

0.6 

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0.6 

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.000059 

.01076 

0.4 

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0.4 

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. 000026 

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+ •2 

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0.4 

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0.6 

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0.6 

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0.8 

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0.8 

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I.O 

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I.O 

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1.2 

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1.2 

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1-4 

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1.4 

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1.6 

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1.6 

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I.s 

'.02761 

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1.8 

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2.0 

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2.0 

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2.2 

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•03554 

2.2 

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2.4 

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.000706 

.03854 

2.4 

•03541 

.000703 

•03849 

2.6 

.03804 

.000816 

.04151 

2.6 

.03792 

.000813 

.04145 

2.8 

.04052 

.000933 

. 04446 

2.8 

.04039 

.000929 

.04439 

3-0 

.04294 

.001056 

.04737 

3.0 

.04280 

.001051 

•04730 

3-2 

.04533 

.001185 

.05026 

3.2 

. .04517 

.001179 

.05018 

3-4 

.04767 

.001320 

.05312 

3-4 

.04749 

.001313 

•05303 

3-6 

.04997 

. 001460 

•05596 

3-6 

.04978 

.001453 

.05586 

3.8 

.05223 

.001607 

.05877 

3-8 

.05202 

.001598 

.05867 

4.0 

.05445 

.001758 

.06157 

4.0 

.05423 

.001748 

.06145 

4.2 

.05663 

.001914 

.06434 

4.2 

.05640 

.001903 

.06421 

4.4 

.05878 

.002075 

.06709 

4.4 

.05854 

.002063 

.06695 

4.6 

.06090 

.002242 

.06982 

4.6 

.06064 

.002228 

.06967 

4.8 

.06299 

.002414 

•07253 

4.8 

.06271 

.002399 

.07237 

5.0 

.06504 

.002590 

.07521 

5-0 

.06475 

.002575 

.07504 

5-2 

.06707 

.002771 

.07788 

5.2 

.06676 

.002755 

•07770 

5.4 

.06907 

.002Q57 

.08053 

5-4 

.06874 

.002939 

.08034 

5.6 

.07104 

.003147 

.08316 

5.6 

.07070 

.003127 

.08296 

5.8 

.07298 

.003341 

.08578 

5.8 

.07263 

.003319 

.08557 

37 


y 

= 5-0 

y = 

5.0 

9 

X 

Y 

T 

9 

X 

Y 

T 

U 

3.4 

. 10465 

.003815 

.07725 

0 

1.4 

.02194 

.00025Q 

.02315 

3-2 

.09119 

.003038 

.07039 

1.6 

.02474 

.000 '^■^2 

.02628 

3-0 

. 08044 

.002455 

.06425 

1.8 

.02748 

.000414 

.02937 

2.8 

•07134. 

.001993 

.05861 

2.0 

.03015 

.000502 

.03242 

2.6 

.06338 

.001618 

.05334 

2.2 

.03276 

.000508 

•03544 

2.4 

.05626 

.001306 

.04834 

2.4 

•03531 

.000700 

•03843 

2.2 

.04978 

.001046 

•04359 

2.6 

.03781 

.000809 

.04139 

2,© 

.04383 

.000828 

.03902 

2.8 

. 04026 

.000925 

.04431 

1.8 

.03829 

.000644 

.03463 

3-0 

. 04266 

. 001046 

.04721 

1.6 

.03311 

.000490 

•03037 

3-2 

.04501 

.001174 

.05008 

1.4 

.02824 

.000362 

.02625 

3-4 

.04732 

.001307 

.05293 

1.2 

.02363 

.000258 

.02224 

3-6 

.04959 

.001446 

•05575 

I.O 

.01925 

.000174 

.01832 

3.8 

.051S2 

.001590 

•05854 

0.8 

.01507 

.000108 

.01451 

4.0 

.05401 

.OUI74O 

.06131 

0.6 

.01108 

.000059 

.01077 

4.2 

.05616 

.001895 

.06406 

0.4 

.00724 

.000026 

.00711 

4-4 

.05828 

.002054 

.06679 

+•2 

•00355 

.000006 

.00352 

4.6 

.06037 

.002218 

.06950 

0.0 

.00000 

.000000 

.00000 

4.8 

.06243 

.0023S7 

.07219 

— .2 

•00343 

.000006 

.00346 

5-0 

.06446 

.002560 

.07486 

0.4 

.00675 

.000023 

.00687 

5-2 

.06646 

.002738 

•07751 

0.6 

.00997 

.000051 

.01022 

5-4 

.06843 

.002920 

.08014 

0.8 

.01309 

.000089 

.01352 

5.6 

.07037 

,003107 

.08275 

I.O 

.01612 

.000137 

.01677 

5.8 

.07228 

.003298 

.08535 

1.2 

.01907 

.000194 

.01998 

6.0 

.07416 

.003493 

.08793 

Y.  = 3 tan  ^ -f- tan 


9 

.0 

.2 

.4 

.6 

.8 

0 

0 

.000 

000 

.010 

472 

\020 

945 

.031 

418 

.041 

893 

I 

.052 

371 

.062 

850 

.073 

333 

.083 

S19 

• 094 

310 

2 

104 

805 

.115 

305 

.125 

811 

. 136 

323 

.146 

S42 

3 

• 157 

367 

.167 

901 

.178 

442 

.188 

993 

.199 

533 

4 

.210 

122 

.220 

702 

.231 

293 

.241 

895 

.252 

509 

5 

.263 

136 

• 273 

775 

.284 

428 

.295 

095 

• 305 

/ i i 

6 

.316 

474 

.327 

186 

• 337 

915 

•348 

661 

• 359 

424 

7 

• 370 

205 

.381 

004 

-391 

823 

.402 

661 

.413 

519 

8 

•424 

398 

•435 

299 

.446 

222 

•457 

167 

.468 

135 

9 

•479 

126 

.490 

143 

.501 

184 

• 512 

251 

• 523 

344 

10 

• 534 

463 

.545 

610 

• 556 

785 

.567 

989 

• 579 

223 

II 

.590 

485 

.601 

779 

.613 

104 

.624 

461 

.635 

850 

12 

.647 

273 

.658 

730 

.670 

221 

.681 

748 

• 693 

310 

13 

.704 

910 

.716 

547 

.728 

222 

• 739 

936 

• 751 

690 

=:  3 tan  cp  tan  ^<p. 


.0 

.2 

.4 

.6 

.8 

0 

14 

.763  483 

.775  319 

.787  196 

•799  115 

.8ri  078 

15 

.823  086 

•835  138 

.847  236 

.859  381 

.871  573 

i6 

.883  813 

.896  103 

.908  442 

.920  832 

•933  275 

17 

.945  769 

-958  317 

.970  919 

.983  577 

.996  291 

i8 

1.009  062 

I. 021  891 

1.034  779 

1.047  727 

1.060  736 

19 

1.073  807 

1.086  941 

I. 100  139 

I. I 13  402 

1.126  731 

20 

I. 140  127 

I. 153  592 

1.167  126 

I. 180  730 

I. 194  407 

21 

1.208  115 

I. 221  978 

1-235  875 

1.249  849 

1.263  901 

22 

1.278  031 

1.292  241 

1.306  532 

1.320  906 

1-335  363 

23 

1.349  906 

1-364  535 

1-379  252 

1.394  058 

1.408  955 

24 

1-423  943 

1.439  025 

1.454  202 

1.469  476 

1.484  847 

25 

1.500  318 

I. 515  890 

I. 531  565 

1.547  344 

1.563  229 

26 

1.579  221 

1-595  323 

1-611  535 

1.627  861 

1.644  301 

27 

1.660  857 

1.677  532 

1.694  327 

1.711  244 

1.728  284 

28 

1-745  450 

1.762  745 

1.780  169 

1.797  726 

1.815  417 

29 

1-833  244 

1.851  209 

1.869  315 

1.887  564 

1.905  959 

30 

1.924  501 

1-943  193 

1.962  038 

1.981  038 

2.000  195 

31 

2.019  513 

2.038  993 

2.058  639 

2.078  452 

2.098  437 

32 

2.118  596 

2.138  931 

2.159  446 

2.180  143 

2.201  026 

33 

2.222  098 

2.243  361 

2.264  820 

2.286  477 

2.308  337 

34 

2.330  401 

2.352  674 

2.375  160 

2.397  862 

2.420  783 

35 

2.443  928 

2.467  300 

2.490  QO4 

2.514  743 

2.538  821 

36 

2.563  143 

2.587  714 

2.612  536 

2.637  615 

2.662  957 

37 

2.688  563 

2.714  441 

2.740  594 

2.767  029 

2.793  748 

38 

2.820  759 

2.848  066 

2.875  675 

2.903  591 

2.931  820 

39 

2.960  368 

2.989  240 

3.018  444 

3-047  983 

3.077  866 

40 

3.108  099 

3.138  688 

3.169  640 

3.200  962 

3.232  661 

41 

3-264  745 

3.297  220 

3-330  095 

3-363  377 

3-397  074 

42 

3-431  194 

3.465  746 

3-500  739 

3.536  180 

3-572  079 

43 

3.608  446 

3.645  289 

3.682  618 

3.720  444 

3-758  776 

44 

3.797  624 

3.837  000 

3.876  914 

3-917  378 

3.958  402 

45 

4.000  000 

4.042  183 

4.084  962 

4.128  352 

4.172  365 

46 

4.217  014 

4.262  314 

4.308  277 

4.354  920 

4.402  257 

47 

4.450  304 

4.499  074 

4.548  585 

4-598  854 

4.649  898 

48 

4-701  734 

4-754  380 

4.807  854 

4.862  177 

4.917  366 

49 

4.973  442 

5.030  427 

5.088  340 

5.147  206 

5-207  045 

50 

• 5.267  881 

5-329  737 

5-392  639 

5.456  611 

5-521  681 

51 

5-587  874 

5.655  218 

5.723  742 

5-793  475 

5.864  448 

52 

5-936  691 

6.010  238 

6.085  117 

6.161  368 

6.239  026 

53 

6.318  124 

6.398  702 

6.480  797 

6.564  452 

6.649  706 

54 

6.736  602 

6.825  183 

6.915  496  - 

7.007  588 

7.101  509 

55 

7-197  304 

7.295  031 

7.394  739 

7.496  488 

7.600  333 

5f) 

7.706  333 

7.814  550 

7.925  047 

8.037  894 

8.153  153 

57 

8.270  898 

8.391  203 

8.514  142 

8.639  795 

8.768  244 

58 

8.899  574 

9.033  869 

9.171  225 

9-3II  731 

9-455  492 

59 

9.602  605 

9-753  175 

9-907  314 

10.065  136 

10.226  756 

39 


VI.  VALUES  OF  X,  T & T FOE  IXTEEVALS  OF  T 


y — 0.00  I y — 0.00 


9 

X 

Y 

T 1 

X 

Y 

T 

0 

6o 

1.73205 

I . 50000 

1.73205 

0 

18 

.32492 

.052786 

. 32492 

59 

1.66428 

1.38492 

I . 66428 

17 

.30573 

.046736 

.30573 

58 

1.60033 

1.28054 

I . 60033 

16 

.28675 

.041112 

.28675 

57 

1.53986 

1-18559 

1-53986 

15 

•26795 

.035898 

•26795 

56 

1.48256 

1.09899 

1.48256 

14 

•24933 

.031082 

•24933 

55 

1.42815 

1.01980 

1.42813 

13 

.23087 

.026650 

•23087 

54 

1.37638 

•947215 

1.37638 

12 

.21256 

.022590 

.21256 

53 

1.32704 

.880524 

1.32704 

II 

.19438 

.018892 

• 19438 

52 

1.27994 

.819125 

1.27994 

10 

•17633 

•015546 

•17633 

51 

1 .234QO 

.762486 

1.23490 

9 

.15838 

.012543 

.15838 

50 

I. 19175 

.710138 

1.19175 

8 

.14054 

.009876 

• 14054 

49 

I. 15037 

.661674 

I. 15037 

7 

.12279 

.007538 

.12279 

48 

I .11061 

.616730 

I. 11061 

6 

.10510 

•005524 

.10510 

47 

1.07237 

•574987 

1.07237 

5 

.08749 

.003S27 

.08749 

46 

1-03553 

.536162 

1-03553 

4 

.06993 

.002445 

.06993 

45 

I .00000 

. 500000 

I .00000 

3 

.05241 

.001373 

.05241 

44 

.96569 

.466278 

.96569 

2 

•03492 

.000610 

.03492 

43 

•93252 

•434792 

•93252 

+i 

.01746 

.000152 

.01746 

42 

. 90040 
.86929 

•405363 

.377830 

.90040 

.86929 

0 

00000 

000000 

00000 

40 

.83910 

•352044 

.83910 

y = 

O.OI 

39 

.80978 

•327875 

.80978 

X 

Y 

"T 

38 

37 

.78129 

•75355 

.305204 

.283922 

.78129 

•75355 

i 

0 

36 

.72654 

.263932 

•72654 

60 

1-77949 

1 .55885 

1.75552 

35 

.70021 

•245145 

.70021 

59 

1 1.70679 

1-43539 

1-6S533 

34 

.67451 

.227481 

•67451 

58 

1-63857 

1.32404 

1.6192S 

33 

.64941 

.210865 

.64941 

57 

1-57437 

1.22324 

1.55697 

32 

.62487 

.195231 

.62487 

56 

1.513S0 

1.13170 

1.49806 

31 

.60086 

.180517 

.60086 

55 

1-45651 

1.04S31 

1.44222 

30 

.57735 

.166667 

•57735 

54 

I .40219 

.97214 

1.38919 

29 

.55431 

.153629 

•55431 

53 

1.35058 

.90238 

1 • 33873 

28 

•53171 

•141358 

•53171 

52 

1-30144 

• S3834 

1 . 29063 

27 

•50953 

. 129808 

•50953 

51 

1.25458 

-77941 

1 . 2446S 

26 

-48773 

.118942 

.48773 

50 

I . 209S0 

.72503 

1.20073 

25 

.46631 

.108721 

.46631 

49 

I . 16694 

.67488 

1.15861 

24 

.44523 

.oqqii4 

.44523 

48 

1.12585 

.62843 

I .11820 

23 

.42448 

. 090090 

.42448 

47 

I . 08640 

.53530 

1.07935 

22 

.40403 

.081619 

•40403 

46 

1.04847 

-54537 

I .04196 

21 

.38386 

.073676 

.38386 

45 

I. 01192 

.50S1S 

1.00593 

20 

.36397 

.066237 

.36397 

44 

.97669 

•47355 

.97116 

19 

•34433 

.059281 

•34433 

43 

.94267 

.44127 

•93757 

40 


y -- 

= O.OI 

y = 

0.01 

9 

X 

Y 

T 

9 

X 

Y 

T 

0 

42 

.90978 

.41114 

.90507 

0 

4 

.06988 

.002443 

. 06990 

41 

.87795 

.38297 

.87361 

5 

.08741 

.003823 

.08745 

40 

.84710 

.35662 

.84309 

6 

. 10499 

.005516 

.10505 

39 

.81718 

.33195 

.81347 

7 

.12264 

.007525 

. I227I 

38 

'.78812 

.30883 

.78469 

8 

. 14034 

.009857 

. 14044 

37 

.75986 

.28715 

.75670 

9 

.15813 

.012516 

. 15826 

36 

.73237 

.2668: 

.72944 

10 

. 17602 

.015509 

.17618 

35 

.70559 

.24769 

. 70290 

II 

,19400 

.018843 

. 19420 

34 

.67947 

.22974 

.57698 

12 

.21211 

.022526 

.21234 

33 

.65398 

.21287 

.65169 

13 

.23034 

.026568 

.23060 

32 

.62908 

.19701 

.62697 

14 

.24870 

.030978 

. 24902 

31 

.60473 

. 18209 

.60279 

15 

.26723 

.035769 

.26759 

30 

.58091 

.168051 

.57913 

16 

.28592 

.040952 

.28633 

29 

.55758 

.154847 

.55594 

17 

.30479 

.046543 

.30526 

28 

.53470 

.142427 

.53320 

18 

.32385 

.052554 

.32439 

27 

'51226 

.130745 

.51089 

19 

.34313 

.059005 

.34373 

26 

.49023 

.119760 

.48898 

20 

.36262 

.065909 

.36330 

25 

.46859 

.109433 

.46744 

21 

.38236 

.073290 

.38311 

24 

.44729 

.099733 

.44626 

22 

.40236 

.081168 

.40319 

23 

.42635 

.090623 

.42541 

23 

.42263 

.089565 

.42355 

22 

.40572 

.0S2077 

.40487 

24 

.44320 

.098508 

.44421 

21 

.38539 

.074067 

.38462 

25 

.46407 

. 108022 

.46519 

20 

.36534 

.066569 

.36465 

26 

.48528 

.118139 

.48650 

19 

.34555 

.059561 

.34494 

27 

.50684 

. 128889 

.50818 

i8 

.32601 

.053021 

.52546 

28 

.52878 

. 140309 

.53024 

17 

. 30669 

.046931 

.30621 

29 

.55111 

.152437 

.55270 

i6 

.28758 

.041272 

.28717 

30 

.57387 

.165314 

.57560 

15 

.26868 

.036020 

.26831 

31 

.59707 

.178985 

. 59896 

14 

.24996 

.031187 

.24964 

32 

.62075 

.193499 

.62281 

13 

.23141 

.026734 

.23114 

33 

,.64494 

.208911 

.64717 

12 

.21302 

.022655 

.21279 

34 

.66967 

.225279 

.67208 

II 

.19476 

.018941 

.19457 

35 

.69497 

.242668 

.69758 

10 

.17664 

.015583 

.17649 

36 

.72087 

.261147 

.72370 

9 

.15863 

.012570 

.15850 

37 

.74742 

.280795 

. 75048 

8 

.14074 

.ooq8q4 

. 14064 

38 

.77465 

.301694 

.77796 

7 

.12294 

.007550 

.12286 

39 

.80262 

.323939 

.80619 

6 

.10521 

.005531 

.10516 

40 

.83135 

.347631 

.83521 

5 

.08757 

.003832 

.08752 

41 

. 86092 

.372884 

.86509 

4 

.06998 

.002447 

.06995 

42 

.89136 

.399820 

.89586 

3 

.05244 

.001374 

.05242 

43 

.92274 

.428576 

.92761 

2 

.03493 

.000610 

.03493 

44 

.95512 

.459307 

.96038 

.01746 

.000152 

.01746 

45 

.98856 

.492182 

.99426 

+ 

+ 

+ 

46 

I. 02315 

.527388 

1.02931 

0 

00000 

000000 

00000 

47 

1.05896 

.565132 

I .06564 



+ 



48 

1.09608 

.605648 

1.10331 

— I 

.01745 

.000152 

.01745 

49 

1.13461 

.649198 

I . 14245 

2 

.03490 

.000610 

.03491 

50 

1.17464 

. 696076 

1.18315 

3 

.05238 

.001373 

.05239 

1.21629 

.746612 

1.22554 

41 


Y-- 

= 0.02 

Y = 

0.02 

9 

X 

Y 

T 

9 

X 

Y 

T 

0 1 
52 

1.25968 

.801177 

1.26976 

0 

27 

.51505 

. I3I7O2 

.51227 

53 

1.30496 

.860189 

1-31593 

26 

•49277 

.120594 

.49024 

54 

1.35226 

.924126 

1.36424 

25 

.47090 

. HOI59 

.46859 

55 

1.40176 

•993530 

1.41486 

24 

•44939 

. 100361 

•44730 

56 

1-45363 

r .069017 

1.46799 

23 

.42825 

.091165 

.42635 

57 

1.50807 

I.I5I292 

1.52384 

22 

•40743 

.082542 

•40572 

58 

1-5653^ 

1.241166 

1.58267 

21 

•38693 

.07^464 

•38539 

59 

1-62559 

1-339565 

1.64476 

20 

.36672 

.066906 

•36534 

6o 

1.68919 

1-447563 

I. 7 1042 

19 ' 

18 

.34678 

•059845 

•34555 

.32600 

.32710 

•053259 

= 0.02 

17 

.30765 

.047128 

. 30669 

Y = 

16 

.28843 

.041434 

•28759 

X 

Y 

T 

15 

.26942 

.036161 

.26868 

9 

14 

13 

.25060 

.23196 

.031203 

.026818 

.24996 

.23141 

0 

6o 

1-83254 

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5 

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53 

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6 

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. 10023 

54 

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•94905 

7 

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55 

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8 

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56 

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1.00169 

9 

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57 

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I . 02926 

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58 

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1-05773 

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59 

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1.08717 

12 

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1.11765 

13 

.19152 

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14 

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r = 

15 

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. 24069 

: I . I 

i6 

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9 

X 

Y 

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17 

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0 

19 

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15 

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20 

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21 

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13 

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22 

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12 

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23 

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24 

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10 

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25 

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9 

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26 

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8 

. 1 7069 

.012826 

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27 

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7 

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y 

= 1. 1 

y = 

1.2 

X 

Y 

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0 

6 

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4 

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42 

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3 

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43 

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2 

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9 

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14 

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8 

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9 

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10 

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9 

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8 

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12 

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7 

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6 

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15 

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+ 

+ 

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“1“ 

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22 

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23 

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24 

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25 

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4 

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26 

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5 

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27 

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6 

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28 

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29 

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30 

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9 

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32 

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33 

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12 

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34 

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35 

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36 

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15 

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37 

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16 

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17 

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39 

1 .48191 

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18 

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75 


7=1.2 


Y = 1-3 


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21 

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4 

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27 

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7 

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29 

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9 

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32 

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33 

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12 

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34 

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13 

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35 

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14 

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36 

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37 

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16 

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38 

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19 

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22 

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23 

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45 

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24 

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25 

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26 

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y 

==  1-3 

27 

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X 

Y 

T 

28 

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29 

30 

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. 36600 

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u 

13 

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31 

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12 

II 

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.26731 

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' 32 
33 

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. 103460 
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10 

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34 

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9 

8 

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. 18220 
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35 

36 

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• 130543 

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7 

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37 

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6 

5 

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38 

39 

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4 

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40 

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3 

2 

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41 

42 

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43 

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44 

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+ 

+ 

+ 

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y 

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r = 

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9 

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Y 

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f 

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0 

12 

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.27842 

0 

34 

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35 

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10 

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36 

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9 

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37 

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8 

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38 

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7 

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39 

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40 

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5 

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4 

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42 

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3 

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43 

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2 

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44 

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+ 

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+ 

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+ 

45 

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2 

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Y 

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3 

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4 

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5 

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II 

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6 

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10 

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7 

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9 

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8 

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9 

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7 

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10 

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6 

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II 

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5 

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12 

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4 

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13 

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3 

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14 

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2 

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15 

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+ 

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+ 

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+ 

16 

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17 

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0 

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18 

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— 

“t" 

— 

19 

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— I 

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20 

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2 

.03324 

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21 

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3 

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22 

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4 

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23 

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5 

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24 

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6 

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25 

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7 

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26 

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8 

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27 

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9 

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28 

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10 

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29 

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30 

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12 

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31 

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13 

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32 

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14 

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33 

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15 

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77 


r 

— 1.6 

y = 

1.6 

9 

X 

Y 

T 

9 

X 

Y 

T 

0 

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0 

0 

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17 

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+ 



19 

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20 

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2 

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21 

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22 

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4 

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23 

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24 

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27 

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9 

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28 

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10 

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29 

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30 

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12 

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31 

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13 

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32 

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14 

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33 

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15 

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34 

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16 

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35 

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17 

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36 

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18 

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37 

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19 

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20 

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39 

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21 

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40 

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22 

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41 

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23 

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42 

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24 

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43 

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25 

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44 

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26 

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45 

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27 

28 

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29 

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y 

= 1.6 

30 

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31 

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X 

Y 

T 

32 

.36169 

.095123 

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9 

33 

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0 

34 

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35 

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9 

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36 

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8 

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37 

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7 

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3 

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42 

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2 

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43 

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44 

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+ 

+ 

+ 

45 

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78 


Y 

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9 

X 

Y 

T 

9 

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0 

10 

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0 

37 

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38 

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39 

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7 

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40 

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6 

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5 

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43 

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3 

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44 

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2 

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45 

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+ 

+ 

+ 

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+ 

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9 

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3 

0 

4 

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9 

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5 

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8 

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6 

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8 

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5 

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9 

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4 

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10 

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3 

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2 

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12 

. 16292 

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13 

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+ 

+ 

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0 

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4 

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9 

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27 

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12 

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.18450 

28 

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13 

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29 

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14 

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31 

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16 

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32 

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17 

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18 

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34 

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19 

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35 

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20 

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36 

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21 

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79 


I 


7 

= 1-9 

7 = 

1-9 

9 

X 

Y 

T 

f 

X 

Y 

T 

0 

22 

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0 

7 

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23 

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8 

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24 

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25 

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26 

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27 

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12 

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28 

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13 

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29 

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14 

. 18007 

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30 

.33066 

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15 

. 19016 

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31 

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16 

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32 

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. 090460 

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17 

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.028470 

.25202 

33 

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•095875 

.47560 

18 

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34 

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. 101485 

.49018 

19 

.22865 

.034612 

.27904 

35 

.37319 

. 107298 

•50493 

20 

.23789 

.037881 

.29251 

36 

.38163 

.113323 

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21 

.24699 

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37 

.39007 

.119569 

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22 

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3a 

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. 126044 

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23 

.26486 

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39 

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. 132760 

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24 

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40 

.41541 

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25 

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41 

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26 

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42 

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27 

. 29948 

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43 

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. 162259 

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28 

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44 

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•64707 

29 

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45 

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.66421 

30 

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■ IHBII 

31 

•33307 

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32 

.34135 

.088343 

.45664 

y 

= 1.9 

33 

•34961 

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X 

Y 

34 

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.099053 

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f 

T 

35 

. 36606 

.0104699 

•49978 

36 

37 

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0 

9 

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8 

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•17377 

33 

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7 

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•14531 

39 

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. 129407 

•55969 

6 

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. 008003 

. I20I2 

40 

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5 

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41 

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4 

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42 

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3 

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43 

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2 

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44 

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+ 

.000160 

+ 

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1 

45 

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0 

.00000 

. 000000 

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— 

+ 

— 

7 = 

2.0 

— I 

.01691 

.000146 

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2 

.03283 

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9 

X 

Y 

T 

3 

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1 

4 

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0 

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5 

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8 

6 

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. 004440 

. 09669 

7 

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•14744 

80 


r 

==  2.0 

7 = 

= 2.  I 

<p 

\ X 

Y 

T 

9 

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Y 

T 

0 

6 

. I4I40 

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0 

40 

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5 

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41 

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3 

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. 00000 

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45 

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O 

— 

+ 

— 

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— I 

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2 

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9 

1 

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Y 

T 

3 

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6 

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2 

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12 

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+ 

+ 

+ 

14 

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0 

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+ 



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17 

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3 

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4 

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20 

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24 

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9 

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10 

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26 

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II 

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27 

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12 

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28 

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29 

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14 

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30 

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15 

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31 

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16 

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32 

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17 

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33 

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34 

, .35131 

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19 

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35 

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20 

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36 

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37 

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22 

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38 

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23 

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39 

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24 

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81 


y 

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9 

X 

Y 

T 

9 

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25 

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0 

10 

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26 

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27 

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12 

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28 

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13 

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29 

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14 

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30 

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15 

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31 

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32 

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17 

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18 

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35 

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20 

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37 

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40 

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25 

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41 

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42 

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27 

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30 

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31 

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32 

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y 

; 2.2 

33 

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34 

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X 

Y 

T 

35 

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9 

36 

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0 

37 

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8 

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38 

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7 

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39 

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6 

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40 

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5 

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41 

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4 

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42 

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43 

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2 

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44 

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45 

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1 

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3 

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4 

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8 

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2 

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9 

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82 


Y 

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9 

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Y 

T 

9 

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Y 

T 

0 

0 

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7 

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+ 

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4 

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2 

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3 

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2 

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2 

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4 

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12 

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7 

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15 

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12 

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19 

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13 

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20 

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14 

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21 

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15 

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22 

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16 

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23 

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17 

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24 

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18 

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25 

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26 

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20 

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27 

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21 

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28 

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22 

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29 

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23 

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30 

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24 

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31 

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25 

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32 

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26 

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33 

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27 

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34 

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28 

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35 

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29 

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36 

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30 

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37 

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. 106430 

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31 

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38 

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32 

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.43669 

39 

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.53805 

33 

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.084041 

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40 

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.123961 

.55272 

34 

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.088830 

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41 

.38516 

.130237 

.56761 

35 

•33554 

.093786 

•47713 

42 

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.136747 

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36 

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.098916 

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43 

•39988 

.143501 

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37 

•34991 

. 104227 

.50481 

44 

.40727 

.150513 

.61378 

33 

.35708 

.109727 

.51891 

45 

.41468 

.157795 

.62973 

39 

.36424 

•115425 

•53320 

83 


r 

= 2.5 

y = 

= 2.6 

9 

X 

Y 

T 

9 

X 

Y 

T 

0 

40 

•37140 

.121330 

•54769 

0 

28 

.28025 

.061254 

•38134 

41 

•37857 

.127451 

.56240 

29 

.28752 

.065206 

•39417 

42 

•38575 

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•57734 

30 

•29475 

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.40707 

43 

•39293 

. 140384 

•59253 

31 

.30192 

.073520 

.42006 

44 

.40013 

. 147220 

.60799 

32 

.30906 

.077893 

•43315 

45 

.40736 

.154318 

.62373 

33 

.31616 

.082416 

•44635 

= 2.5 

34 

.32323 

.087096 

•45967 

r 

35 

36 

•3302S 

•33730 

.091939 

.096950 

•47312 

.48672 

X 

Y 

9 

T 

37 

38 

•34431 

•35131 

.102138 
• 107509 

. 50049 
.51442 

0 

7 

. 23004 

.017756 

.16361 

39 

•35830 

.113073 

.52854 

6 

.16193 

.0099-27 

. 12907 

40 

•36530 

.118838 

.542S6 

5 

.11987 

.005856 

. 10188 

41 

•37229 

.124813 

•55739 

4 

.08781 

.003322 

.07816 

42 

•37930 

.131008 

•57213 

3 

.06134 

.001696 

.05663 

43 

.38631 

•137435 

•58715 

2 

.03851 

.000695 

.03665 

44 

•39334 

• 144105 

.60242 

+i 

.0x828 

+ 

.00000 

.000162 

+ 

.000000 

.01786 

+ 

.00000 

45 

.40038 

.151030 

•61797 

O 

2.6 

— 

+ 



y = 

— r 

.01675 

.000144 

,01710 

I 

X 

Y 

T 

2 

3 

.03225 

.04673 

.000548 

.001179 

•03355 

9 

u 

4 

.06035 

.002011 

.06491 

6 

. 16780 

.010425 

.13110 

5 

.07324 

.003025 

.07996 

5 

. 12232 

.006019 

.10283 

6 

.08549 

. 004204 

.09465 

4 

.08892 

.003379 

.07863 

7 

.09719 

.005536 

• 10903 

3 

.06182 

.001714 

.05685 

8 

. 10841 

.007012 

.12314 

2 

.03869 

.000699 

•03674 

9 

.11919 

.008623 

.13701 

+i 

.01832 

.000163 

.01788 

lO 

.12959 

.010362 

.15067 

+ 

+ 

+ 

II 

.13964 

.012226 

.16415 

0 

,00000 

.000000 

.00000 

12 

•14939 

.014208 

.17746 

— 

+ 



13 

.15886 

.016307 

.19062 

— I 

.01672 

.000144 

.01708 

14 

.16808 

.018519 

.20367 

2 

.03216 

.000547 

•03350 

15 

.17706 

.020843 

.21660 

3 

.04655 

.001173 

.04936 

i6 

.18584 

.023277 

•22945 

4 

.06005 

.001999 

•06475 

17 

. 19443 

.025821 

. 24222 

5 

.07282 

. 003002 

.07972 

i8 

.20285 

.028475 

•25493 

6 

.0S493 

.004168 

•09433 

19 

.21110 

.031238 

.26759 

7 

.09649 

.005484 

.10862 

20 

.21922 

.034111 

.28021 

8 

.10756 

. 006940 

.12264 

21 

.22720 

.037095 

.29281 

9 

.ii8ig 

.00S529 

.13642 

22 

.23506 

.040192 

•30540 

10 

.12844 

.010243 

• 14998 

23 

.24281 

.043403 

•31799 

II 

•13S34 

.012078 

•16335 

24 

•25047 

.046730 

.33060 

12 

• 14793 

.014029 

•17655 

25 

.25803 

.050176 

•34322 

13 

•15724 

.016093 

.1S961 

26 

.26550 

•053743 

•35588 

14 

. 16630 

.01S268 

.20254 

27 

. .27291 

•057435 

.36858 

15 

•17514 

.020552 

.21536 

84 


y 

= 2.6 

r = 

2.7 

9 

X 

Y 

T 

9 

X 

Y 

T 

U 

i6 

.18376 

.022943 

.22810 

0 

4 

.05976 

.001985 

.06459 

17 

.19219 

•025441 

.24075 

5 

.07240 

.002979 

.07948 

18 

. 20045 

.028045 

•25334 

6 

.08439 

.004X32 

.09401 

19 

.20855 

.030756 

<26588 

7 

.09581 

.005432 

. 10822 

20 

.21651 

•033574 

.27838 

8 

.10673 

.006870 

.12215 

21 

.22434 

.036501 

.29086 

9 

.11722 

.008437 

•13583 

22 

.23205 

•039537 

■30333 

10 

.12732 

.010127 

• 14929 

23 

•23965 

.042684 

•31579 

II 

.13708 

.011934 

.16256 

24 

.24714 

•045944 

.32827 

12 

.14652 

•013855 

•17567 

25 

■25455 

.049319 

.34076 

13 

.15569 

.015286 

. 18862 

26 

.26188 

.052813 

•35329 

14 

. 16460 

.018025 

.20144 

27 

.26913 

.056428 

.36586 

15 

.17328 

.020270 

.21416 

28 

.27631 

.060167 

.37848 

16 

.18175 

.022620 

.22678 

29 

•28343 

.064035 

•39117 

17 

. 19004 

.025074 

.23932 

30 

.29050 

.068034 

.40393 

18 

.19815 

.027631 

.25180 

31 

.29752 

.072171 

.41678 

19 

.20610 

.030293 

. 26422 

32 

•30450 

.076449 

■42973 

20 

.21392 

•033059 

.27661 

33 

•31145 

.080873 

.44278 

21 

.22160 

•035930 

.28897 

34 

•31836 

.085450 

•45595 

22 

.22916 

.038907 

•30131 

35 

•32525 

.090184 

.46926 

23 

.23661 

.041993 

.31366 

36 

.33212 

.095084 

.48271 

24 

.24396 

.045190 

.32601 

37 

•33897 

.100155 

.49631 

25 

.25122 

.048498 

•33838 

38 

•34582 

. 105405 

.51009 

26 

.25840 

.051922 

•35078 

39 

•35265 

.110842 

.52405 

27 

.26550 

•055464 

.36323 

40 

•35948 

.116475 

.53820 

28 

.27254 

.059127 

•37572 

41 

.36632 

. I223I2 

.55256 

29 

•27952 

.062915 

.38828 

42 

•37316 

.128365 

•56715 

30 

.28644 

.066832 

.40091 

43 

.38001 

.134642 

.58198 

31 

.29331 

.070883 

.41362 

44 

.38687 

.141136 

•59707 

32 

.30015 

.075070 

.42643 

45 

.39376 

.147919 

.61244 

33 

.30695 

.079401 

•43935 

•45238 

34 

•31371 

.083880 

35 

•32045 

.088513 

•46554 

r 

= 2.7 

36 

.32717 

-093307 

.47884 

X 

Y 

T 

37 

•33388 

.098267 

.49230 

9 

38 

39 

•34057 

.34725 

. 103402 
. IOS72O 

•50592 

•51972 

0 

6 

.17470 

.011021 

•13339 

40 

•35394 

.114228 

•53372 

5 

. 12496 

.006198 

. 10386 

41 

.36062 

•119935 

■54792 

4 

.09007 

•003439 

.07912 

42 

•36731 

.125852 

•56235 

3 

.06230 

.001732 

•05707 

43 

•37401 

.131989 

•57701 

2 

.03885 

,000704 

.03682 

44 

.38071 

.138356 

■ -59193 

+i 

•01835 

.000163 

.01790 

45 

•38744 

• 144965 

.60712 

+ 

+ 

+ 

0 

.00000 

. 000000 

.00000 

— I 

.01669 

.000144 

.01707 

2 

.03207 

.000544 

• 03345' 

3 

.04636 

.001167 

.04927 

85 


Y 

= 2.8 

r = 

2.9 

9 

X 

Y 

T 

9 

X 

Y 

T 

0 

6 

.18312 

.011761 

. 13603 

0 

40 

.34861 

.112089 

.52940 

5 

. 12786 

.006395 

• 10493 

41 

•35515 

.117674 

• 54345 

4 

.09130 

.003502 

.07961 

42 

.36170 

. 123463 

• 55772 

3 

.06282 

.001751 

.05728 

43 

.36825 

. 129466 

.57222 

2 

.03903 

.000708 

.03689 

44 

•37481 

•135694 

.58698 

+i  . 

.01839 

+ 

.000163 

+ 

.01791 

+ 

45 

•38139 

.142158 

.60200 

O 

. 00000 

. 000000 

.00000 

— I 

.01667 

+ 

.000143 

.01706 

Y = 

2.9 

2 

•03197 

.000542 

•03341 

3 

.04618 

.001161 

.04917 

9 

X 

Y 

T 

4 

•05947 

.001973 

.06442 

5 

•07199 

.002957 

•07925 

0 

. 19388 

6 

•08385 

.004098 

.09370 

6 

.012730 

.13921 

5 

• 13105 

.006616 

. 1061 I 

7 

8 

.09513 

• 10592 

.005383 

.006802 

.10783 
. 12167 

4 

.09258 

.003570 

.08015 

9 

.11627 

.008348 

.13526 

3 

•06334 

.C01772 

•05753 

10 

II 

.12623 

•13584 

.010014 

.011795 

.14863 
. 16180 

2 

.03921 

.01842 

.000712 

.000164 

.03699 

.01793 

12 

•I45I4 

.013687 

. 17480 

0 

.00000 

.000000 

.ocooo 

13 

.15416 

.015687 

.18765 

— I 

.01664 

.000143 

.01704 

14 

•16293 

.017791 

.20037 

2 

.03188 

.000540 

• 03335 

15 

.17147 

.019999 

.21298 

3 

.04600 

.COII55 

.04906 

i6 

.17980 

.022309 

.22550 

4 

.05918 

.001960 

.06426 

17 

.18794 

.024721 

•23793 

5 

.07158 

.C02935 

.07902 

i8 

.19591 

.027234 

.25030 

6 

.08332 

.004064 

.09339 

19 

•20373 

.029848 

.26261 

7 

.09448 

.C05335 

.10744 

20 

.21140 

.032563 

.27489 

8 

.10513 

.006737 

. I2II9 

21 

.21894 

.035382 

.28713 

9 

•11534 

.008263 

• 13469 

22 

.22636 

.038304 

.29936 

10 

.12517 

.009906 

.14797 

23 

•23367 

.041332 

•31159 

II 

• 13464 

.011661 

. 16104 

24 

.24088 

. 044468 

.32382 

12 

. 14380 

.013525' 

•17395 

25 

. 24800 

•047713 

.33608 

13 

.15269 

.015494 

. 18670 

26 

•25504 

.051070 

•34836 

14 

. 16132 

.017566 

• 19933 

27 

.26201 

•054543 

. 36068 

15 

.16972 

.01973S 

.2IIS3 

28 

.26891 

•058133 

•37305 

16 

.17791 

.022010 

.22424 

29 

•27574 

.06IS46 

•38548 

17 

.18592 

.0243S1 

•23657 

30 

.28253 

.065684 

•39798 

18 

.19375 

.026S51 

.24SS3 

31 

.28926 

.060652 

•41057 

19 

.20143 

.020420 

.26104 

32 

.29596 

•073755 

•42325 

20 

.20897 

.032088 

.27320 

33 

.30262 

.077996 

•43603 

21 

.21637 

.034856 

• 2S534 

34 

.30924 

.082383 

.44892 

22 

.22366 

.037726 

.29746 

35 

•31584 

.086919 

.46195 

23 

.23083 

. 04069S 

.3095 8 

36 

•32242 

.091612 

•47511 

24 

.23791 

■043776 

.32170 

37 

.32898 

.006460 

.48842 

25 

■24490 

. 046960 

•33383 

38 

•33553 

.101495 

.50190 

26 

.251S1 

.050254 

.34600 

39 

.34208 

. 106699 

■51555 

27 

.25S64 

.053660 

.35S20 

8(3 


Y = 2.9 


Y = 3-1 


X 

Y 

T 

9 

X 

Y 

T 

0 

28 

.26541 

.057182 

•37045 

. 17608 

.021720 

•22303 

29 

.27211  . 

.060822 

.38276 

17 

.18396 

.024053 

•23526 

30 

.27876 

.064585 

•39514 

18 

. 19166 

.026481 

.24742 

31 

.28537 

.06S475 

.40761 

19 

. 19921 

.029007 

.25952 

32 

.29193 

.072496 

.42016 

20 

.20661 

.031620 

.27158 

33 

.29845 

.076653 

.43281 

21 

.21389 

•034349 

.28361 

34 

•30495 

.080951 

•44553 

22 

.22104 

.037168 

.29563 

35 

.31141 

.085396 

•45847 

23 

.22810 

.040088 

•30763 

36 

.31786 

.089994 

•47150 

24 

•23505 

.043110 

•31965 

37 

•32429 

.094751 

.48467 

23 

.24191 

.046236 

•33167 

3B 

.33070 

•099674 

.49801 

26 

.24869 

•049470 

•34372 

39 

.33711 

.104771 

•51153 

27 

.25539 

•052813 

•35581 

40 

•34351 

. I 10049 

•52523 

28 

. 26203 

.056269 

■36794 

41 

.34992 

•115517 

•53913 

29 

.26861 

.059841 

■38014 

42 

•35632 

.121185 

•55325 

30 

■ -27513 

•063533 

.39240 

43 

.36274 

. 127062 

•56759 

31 

.28161 

.067348 

.40474 

44 

.36916 

■133158 

•58219 

32 

.28805 

.071292 

.41717 

45 

■37560 

•139485 

•59705 

33 

34 

.29444 

.30081 

•075368 

•079583 

.42970 

•44234 

35 

■30715 

•083941 

■45510 

Y 

= 3-0 

36 

■31347 

.0S8448 

. 46800 
.48105 

37 

•31977 

.093110 

w 

/ 

X 

Y 

T 

38 

. 32606 

.097936 

.49426 

39 

■33234 

. 102930 
. 10S102 

•50763 

0 

40 

•33861 

.52119 

5 

•13457 

.006862 

.10736 

41 

•344S9 

.113460 

■ 53495 

4 

■09393 

.003641 

.07068 

42 

•35116 

. II9OI2 

• 54893 

3 

.06387 

.001791 

•05775 

43 

•35745 

. 124769 

•56313 

2 

•03939 

.000717 

•03707 

44 

•36374 

• 130741 

•57758 

+ I 

.01846 

+ 

. 00000 

.000164 

+ 

. 000000 

•01795 

+ 

.00000 

45 

•37004 

.136938 

.59229 

0 

— 

+ 

— 

r = 

3-1 

— I 

.01662 

.000142 

.01703 

2 

•03179 

.000538 

•03331 

X 

Y 

3 

.04582 

.001149 

.04897 

9 

T 

4 

.05890 

.001948 

.06411 

0 

5 

.07119 

.002914 

.07880 

5 

•13855 

.007143 

.10875 

6 

.08280 

.004031 

.09310 

4 

•09536 

.003716 

.08126 

7 

.09383 

.005287 

. 10706 

3 

.06442 

.001812 

•05799 

8 

. 10436 

.006672 

.12074 

2 

.03958 

.000721 

•03715 

9 

.11444 

.008178 

•13415 

+i 

.01850 

.000165 

.01797 

10 

.12413 

.009799 

•14733 

4- 

+ 

+ 

II 

•13347 

.011530 

. 16032 

0 

. 00000 

. 000000 

.00000 

12 

.14250 

.013367 

•17313 

— 

+ 

— 

13 

.15125 

.015307 

.18579 

— I 

.01659 

.000142 

.01701 

14 

•15975 

.017346 

.19831 

2 

.03171 

.000536 

.03326 

15 

. 16802 

.019485 

.21072  1 

3 

.04564 

.001143 

.04887 

87 


y 

= 3-1 

y = 

3.2 

9 

X 

Y 

T 

9 

X 

Y 

T 

U 

4 

.05862 

.001936 

.06395 

0 

5 

■ 14309 

.007467 

. IIO27 

5 

' .07080 

.002893 

•07857 

4 

.Oq68q 

.003798 

.08185 

6 

.08229 

.003999 

.09280 

3 

.06500 

.001835 

■05824 

7 

.09320 

.005241 

. 10669 

2 

•03977 

.000726 

■03724 

8 

. 10360 

.006610 

. 12028 

+1 

•01853 

.000165 

■01799 

9 

•11356 

.008097 

•13361 

+ 

+ 

+ 

lO 

.12312 

.009697 

. 14670 

0 

.00000 

.ooooco 

.00000 

11 

12 

•13233 

.14123 

.011404 

.013214 

. 15960 
•17232 

— I 

.01656 

+ 

.000142 

.01700 

13 

.14985 

.015126 

. 18489 

2 

.03162 

.000535 

.03321 

14 

•15823 

•017135 

•19732 

3 

•04547 

■001137 

.04878 

15 

.16637 

.019240 

. 20963 

4 

•05835 

.001924 

.06380 

i6 

•17431 

.021441 

.22184 

5 

.07041 

.002S72 

.07836 

17 

. 18206 

•023736 

•23397 

6 

.08179 

.003067 

.092^1 

i8 

■.18964 

.026125 

. 24603 

7 

.09258 

.005196 

. 10632 

19 

. 19706 

. 028609 

to 

CO 

0 

8 

.10286 

.006548 

.11983 

20 

•20434 

.031187 

■ .26999 

9 

.11269 

.008017 

.1330S 

21 

.21149 

.033861 

.28192 

10 

. I22I3 

.009596 

.14609 

22 

.21852 

.036632 

•29383 

11 

. I3I22 

.O112S0 

.15890 

23 

•22545 

.039501 

•30572 

12 

. 14000 

.013066 

•17153 

24 

.23228 

.042470 

•31764 

13 

•14850 

.014950 

. 18401 

25 

.23902 

.045541 

.32956 

14 

•15675 

.016929 

•19635 

26 

•24567 

.048717 

•34150 

15 

• 16477 

.019003 

.20S57 

27 

.25226 

.052000 

•35348 

16 

.17258 

.021170 

.22069 

28 

.25878 

■055393 

•36550 

17 

.18021 

.023429 

.23272 

29 

•26523 

.058900 

•37758 

iS 

.1S767 

■0257S1 

.24468 

30 

.27164 

.062524 

•38973 

19 

• 19497 

.02S224 

•25659 

31 

.27800 

.066268 

•40195 

20 

.20213 

.030760 

.26845 

32 

.28431 

.070138 

.41427 

21 

.20917 

.033390 

.28028 

33 

.29059 

.074138 

.42668 

22 

.21608 

.036115 

. 29209 

34 

.29684 

.078273 

.43920 

23 

.22289 

.038935 

.30389 

35 

.30306 

.082548 

.45184 

24 

.22961 

.041854 

•31569 

36 

: 30925 

.086969 

.46462 

25 

.23623 

.044872 

.32751 

37 

■31543 

■091542 

•47754 

26 

.24277 

.047993 

•33935 

38 

.32160 

.096273 

.49061 

27 

. 24924 

.05121S 

.35122 

39 

•32776 

. IOII7I 

• 50386 

2S 

•25564 

•054551 

•36314 

40 

■33391 

. 106242 

•51729 

29 

.26199 

•057995 

•37511 

41 

.34006 

.111495 

•53091 

30 

.26828 

.061554 

• 3S715 

42 

.34622 

.116937 

•54475 

31 

•27452 

.065231 

.39927 

43 

•35238 

. 122580 

.55881 

32 

.2S072 

.069030 

•41147 

44 

•35854 

■128433 

•57311 

33 

.28688 

.072957 

•42376 

45 

•36472 

■134506 

•58767 

34 

.29301 

.077016 

.43617 

35 

.29912 

.0S1212 

•44S70 

36 

.30520 

.0S555O 

•46133 

37 

.31127 

.090038 

■47415 

38 

•31732 

.094680 

.4S710 

39 

.32336 

.099485 

.50022 

88 


y 

= 3-3 

3-4 

? 

X 

Y 

T 

f 

X 

Y 

T 

u 

40 

•32939 

. 104460 

•51352 

0 

28 

.25262 

•053742 

•36083 

41 

•33543 

. 10^13 

.52702 

29 

.25885 

.057126 

.37270 

42 

.34146 

• I 1495 1 

.54072 

30 

.26503 

.060623 

.38464 

43 

•34750 

. 120486 

•55464 

31 

.27117 

.064236 

•39665 

44 

•35355 

.126225 

.56881 

32 

.27726 

.067968 

.40874 

45 

•35961 

. 132181 

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33 

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35 

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36 

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r 

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38 

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5 

4 

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4 

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5 

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18 

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19 

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8 

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21 

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9 

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22 

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10 

. 12023 

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23 

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II 

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24 

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12 

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25 

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13 

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26 

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14 

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. 19446 

27 

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• 34902 

15 

. 16170 

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89 


r = 3-5 


Y = 3-6 


X 

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T 

9 

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T 

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0 

7 

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17 

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9 

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10 

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20 

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21 

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12 

• 13649 

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. 16926 

22 

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13 

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23 

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25 

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17 

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27 

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18 

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28 

. 24969 

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19 

. 18910 

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29 

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20 

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30 

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21 

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31 

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22 

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32 

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23 

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33 

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24 

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34 

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25 

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35 

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26 

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36 

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27 

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37 

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28 

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38 

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29 

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39 

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30 

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40 

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31 

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41 

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32 

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42 

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33 

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43 

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34 

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44 

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35 

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45 

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1 .127826 

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36 

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37 

. 29964 

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Y 

= 3-5 

38 

•30537 

.090283 

•47717 

39 

.31110 

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9 

X 

Y 

T 

40 

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41 

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. 104425 

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0 

42 

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. 109478 

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4 

3 

2 

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1.03750 

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43 

44 

45 

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+ 

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+ 

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+ 

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r = 

= 3.6 



+ 

— 

X 

Y 

T 

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u 

4 

3 

2 

3 

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. 04496 

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4 

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5 

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+i 

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6 

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+ 

+ 

+ 

80 


y 

= 3-6 

y = 

3-7 

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X 

Y 

T 

X 

Y 

T 

0 

0 

1 .00000 

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4 

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+ 

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+ 

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4 

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5 

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2 

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7 

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12 

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9 

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13 

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10 

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14 

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15 

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12 

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. 16782 

16 

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13 

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17 

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18 

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15 

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rg 

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16 

. 16467 

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20 

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17 

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21 

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18 

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22 

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25 

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24 

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29 

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26 

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30 

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27 

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31 

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29 

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30 

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34 

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31 

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35 

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36 

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33 

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37 

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34 

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33 

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39 

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36 

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40 

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41 

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91 


r 

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y = 

3-8 

f 

X 

Y 

T 

0 

X 

Y 

T 

0 

43 

44 

45 

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.111242 
. 116489 
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34 

35 

36 

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37 

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r 

= 3.8 

38 

• 29463 

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39 

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X 

Y 

T 

40 

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41 

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4 

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3 

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45 

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4 

0 

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r = 

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4- 



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f 

X 

Y 

T 

2 

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3 

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4 

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7 

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2 

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12 

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3 

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13 

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14 

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15 

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7 

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19 

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12 

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22 

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13 

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23 

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14 

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24 

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15 

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25 

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16 

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26 

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27 

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18 

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28 

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29 

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30 

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21 

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22 

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32 

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23 

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33 

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24 

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92 


r = 39 


r — 4- i 


^ \ 

X 

Y 

T 

9 

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Y 

T 

0 

25 

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16 

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17 

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34 

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32 

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36 

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37 

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38 

39 

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9 

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Y 

T 

40 

41 

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0 

4 

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3 

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3 

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93 


7 

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Y 

T 

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0 

7 

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u 

0 

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•25342 

.06S00S 

•41755 

40 

. 27468 

•083553 

.46573 

37 

.25S10 

.071472 

.42S79 

41 

•27938 

.087565 

•47764 

38 

.26276 

.075051 

.44016 

42 

.28407 

.091719 

•4S973 

39 

.26741 

.078752 

.4516S 

43 

.28877 

.096021 

.50201 

40 

.27206 

.082580 

•46334 

44 

.29346 

. TOO479 

.51449 

41 

.27669 

.086541 

•47517 

45 

.29817 

. 105 100 

•52719 

42 

.28133 

.090641 

.4S718 

9S 


y = 4-9 


y = 5-0 


V 

i ^ 

Y 

T 

f 

1 ^ 

Y 

T 

0 

43 

.2S596 

.094887 

.49938 

0 

16 

. 14822 

.017456 

.20363 

44 

. 29060 

.099287 

.51178 

17 

.15426 

.019245 

■21434 

45 

■29524 

. 103S48 

■52440 

18 

.16015 

.021101 

.22497 

19 

. 16590 

.023024 

•23553 

y 

= 5-0 

20 

.17152 

.025014 

. 24604 

21 

•17703 

.027072 

•25650 

X 

Y 

22 

. 18243 

.029200 

. 26694 

f 

1 

23 

24 

.18773 

.19295 

•031397 

.033665 

•27735 

.28776 

0 

3 

.08044 

.002455 

.06425 

25 

. 19809 

.036007 

.29S16 

2 

.04383 

.000828 

.03902 

26 

•20315 

.038423 

.30858 

+i 

.01925 

.000174 

.01832 

27 

.20A6 

.040916 

.31902 

+ 

+ 

+ 

28 

.21310 

.043488 

•32949 

0 

.000000 

. 000000 

.00000 

29 

.21798 

.046142 

.34000 



+ 

30 

.22282 

.04SS79 

•35056 

— I 

.01612 

.OCOI37 

.01677 

31 

.22762 

.051703 

.36118 

2 

.03015 

.000502 

.03242 

32 

•23237 

.054618 

.37186 

3 

.04266 

.001046 

.04721 

33 

.23709 

.057626 

.38263 

4 

. .05401 

.001740 

.06131 

34 

.24179 

.060730 

•39348 

5 

. 06446 

.002560 

.07486 

35 

• 24645 

.063936 

•40443 

6 

.07416 

•003493 

•08793 

36 

.25109 

.067247 

•41548 

7 

.0S324 

.004527 

. 10060 

37 

•25571 

.070667 

.42666 

8 

.09181 

.005654 

.11294 

38 

.26032 

.074202 

■43796 

9 

.09993 

.006868 

.12497 

39 

.26491 

.077857 

•44940 

10 

.10767 

.00S162 

•13675 

40 

.26950 

.081637 

. 46099 

II 

.11506 

•009533 

.14831 

41 

.27408 

.085548 

•47275 

12 

. 12217 

.010977 

•15967 

42 

.27865 

.089596 

.48468 

13 

. I2Q0I 

.012494 

.170S7 

43 

.28323 

.093789 

.49680 

14 

.13562 

.014080 

. iSigl 

44 

.28781 

.098133 

•50913 

15 

, 14201 

•015734 

.19283 

45 

.29239 

. 102636 

.52167 

yil.  TABLE  OF  VALUES  OF 
L = igf  = 193.1447f  lACHES. 


t 

h 

t 

h 

t 

h 

Inches. 

Inches. 

Inches. 

Inches. 

0.  10 

1-9314 

0.21 

8.5177 

0.32 

19.778 

0.43 

35-713 

.11 

2.3371 

.22 

9.3482 

•33 

21.034 

•44 

37-393 

. 12 

2.7813 

• 23 

10.217 

•34 

22.328 

•45 

39-112 

• 13 

3.2641 

•24 

II. 125 

•35 

23.660 

.46 

40.869 

■ 14 

3-7856 

■ 25 

12.072 

•36 

25.032 

•47 

42 . 666 

• 15 

4-3458 

.26 

13.057 

•37 

26.442 

.48 

44-501 

. 16 

4-9445 

■ 27 

14.080 

•38 

27.890 

•49 

46-374 

• 17 

5-5819 

.28 

15-143 

•39 

29-377 

•50 

48.286 

.18 

6.2579 

• 29 

16.244 

•40 

30.903 

•51 

50.237 

.19 

6.9725 

•30 

17-333 

.41 

32.468 

■52 

52.226 

.20 

7-7258 

• 31 

18.561 

-42 

34-071 

•53 

54-254 

99 


VITL  A GENERAL  TABLE  OF  YALUES  OF  s 
FOR  OGIYAL-HEADED  SHOT. 


Y. 

0 

1 

2 

3 

4 

5 

6 j 

7 

8 

9 

F-s. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet 

Feet. 

Feet,  j 

Feet.  1 

Feet. 

54 

I 

7303 

7250 

7197 

7144 

7092 

7039 

6987 

6935  i 

6883  ! 

6832 

55 

I 

6780 

6729 

6678 

6627 

6577 

6526 

6476 

6426 1 

6376 

6326 

56 

I 

6276 

6227 

6178 

6129 

6080 

6031 

5982 

5934  j 

5886 

5838 

57 

I 

5790 

5742 

5695 

5647 

5600 

5553 

5506 

5459 ' 

5413 

5366 

58 

I 

5320 

5274 

5228 

5182 

5137 

5091 

5046 

5001  1 

4956 

4911 

59 

I 

4866 

4822 

4777 

4733 

4689 

4645 

4601 

4558  ; 

4514 

4471 

60 

I 

4428 

4385 

4342 

4299 

4256 

4214 

4171 

4129  ' 

4087 

4045 

61 

I 

4003 

3962 

3920 

3879 

3838 

3796 

3755 

3714 

3674 

3633 

62 

I 

3593 

3552 

3512 

3472 

3432 

3392 

3353 

3313 

3274 

3234 

63 

I 

3195 

3156 

3117 

3079 

3040 

3001 

2963 

2925 

2886 

2848 

64 

I 

2810 

2772 

2735 

2697 

2660 

2622 

2585 

2548 

2511 

2474 

65 

I 

2437 

2400 

2364 

2327 

2291 

2255 

2218 

2182 

2146 

2III 

66 

I 

2075 

2039 

2004 

1969 

1933 

1898 

1863 

1828 

1793 

1758 

67 

I 

1724 

1689 

1655 

1620 

1586 

1552 

1518 

1484 

1450 

1417 

68 

I 

1383 

1349 

1316 

1283 

1250 

1216 

1183 

1150 

II18 

1085 

69 

I 

1052 

1019 

0987 

0955 

0922 

0890 

0858 

0826 

0794 

0762 

70 

I 

0731 

0699 

0667 

0636 

0605 

0573 

0542 

0511 

0480 

0449 

71 

I 

0418 

0387 

0357 

0326 

0296 

0265 

0235 

0205 

0174 

0144 

72 

I 

0114 

0084 

0055 

0025 

9995 

9966 

9936 

9907 

9S77 

9S48 

73 

9819 

9790 

9761 

9732 

9703 

9674 

9646 

9617 

9588 

9560 

74 

9531 

9503 

9475 

9447 

9419 

9391 

9363 

9335 

9307 

9279 

75 

9252 

9224 

9197 

9169 

9142 

9115 

9087 

9060 

9033 

9006 

76 

8979 

8952 

8926 

8899 

8872 

8846 

8819 

8793 

8 766 

8740 

77 

8714 

8688 

8662 

8636 

8610 

8584 

8558 

8532 

8507 

8481 

78 

8455 

8430 

8404 

8354 

8379 

8329 

8303 

8278 

8253 

8228 

79 

8203 

8179 

8154 

8129 

8104 

8080 

S055 

8031 

8006 

7982 

80 

7958 

7934 

7909 

7885 

7861 

7S37 

7813 

7789 

7766 

7742 

81 

7718 

7694 

7671 

7647 

7624 

7600 

7577 

7554 

7531 

7507 

82 

7484 

7461 

7438 

7415 

7392 

7'369 

7347 

7324 

7301 

7279 

83 

7256 

7234 

7211 

71S9 

7166 

7144 

7122 

7100 

7078 

7055 

84 

7033 

7011 

6990 

6968 

6946 

6924 

6902 

6881 

6859 

6837 

85 

6816 

6794 

6773 

6752 

6730 

6709 

6688 

6667 

6646 

6625 

86 

6604 

6583 

6562 

6541 

6520 

6499 

6478 

6458 

O37 

6417 

87 

6396 

6375 

6355 

6335 

6314 

6294 

6274 

6254 

6233 

6213 

88 

6193 

6173 

6153 

6133 

6113 

6093 

6074 

6054 

6034 

6014 

89 

5995 

5975 

5956 

5936 

5917 

5897 

5878 

5859 

5839 

, 5820 

90 

5801 

5782 

5763 

5744 

5725 

5706 

5687 

566S 

5649 

' 5631 

91 

5612 

5593 

5575 

5556 

5538 

i 5519 

5501 

54S3 

5464 

‘ 5446 

92 

5428 

5410 

5392 

5374 

535& 

( 5338 

5321 

5303 

5285 

526S 

93 

5250 

5232 

5215 

5198 

5180 

5163 

5146 

5129 

5094 

94 

5077 

5060 

5044 

5027 

5010 

4993 

4976 

4960 

' 4943 

4927 

95 

4910 

4894 

4847 

4861 

I 4845 

4829 

4812 

4796 

j 47S0 

4764 

96 

4749 

4733 

4717 

4701 

4686 

! 4670 

4654 

4639 

1 4624 

4608 

97 

4593 

4578 

4562 

; 4547 

I 4532 

4517 

4502 

44S7 

i 4473 

4458 

98 

4443 

4429 

4414 

j 4399 

j 4385 

4371 

1 

4356 

4342 

j 4328 

1 4314 

100 


I 


y. 

0 

1 

2 

3 

4 

5 

8 

9 

F-s. 

Feet. 

Feet. 

Feet. 

Feet 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

99 

4300 

4285 

4271 

4258 

4244 

4230 

4216 

4203 

4189 

4176 

100 

4162 

4149 

413^ 

4123 

4110 

4097 

4084 

4071 

4058 

4045 

lOI 

4033 

4020 

4008 

3995 

3983 

3970 

3958 

3946 

3934 

3921 

102 

3910 

3898 

3886 

3874 

3863 

3851 

3840 

3829 

3817 

3806 

103 

3795 

3784 

3773 

3762 

3751 

3740 

3730 

3719 

3708 

3698 

104 

3687 

3677 

3666 

3656 

3646 

3636 

3626 

3616 

3606 

3596 

105 

3586 

3576 

3567 

3557 

3547 

3538 

3528 

3519 

3510 

3501 

io6 

3491 

3482 

3473 

3464 

3455 

3446 

3438 

3429 

3420 

3411 

107 

3402 

3394 

3385 

3377 

3368 

3360 

3351 

3343 

3334 

3326 

io8 

3318 

3310 

3301 

3293 

3285 

3277 

3269 

3261 

3252 

3244 

109 

3236 

3228 

3220 

3213 

3205 

3197 

3189 

3181 

3173 

3165 

no 

3158 

3150 

3142 

3134 

3127 

3119 

3111 

3103 

3096 

3088 

III 

3080 

3073 

3065 

3058 

3050 

3043 

3035 

3028 

3020 

3013 

II2 

3005 

2998 

2990 

2983 

2976 

296s 

2961 

2953 

2946 

2939 

II3 

2931 

2924 

2917 

2910 

2902 

2895 

2888 

2881 

2874 

2867 

II4 

2859 

2852 

2845 

2838 

2831 

2824 

2817 

2810 

2803 

2796 

115 

2789 

2782 

2775 

2768 

2761 

2754 

2747 

2740 

2733 

2727 

II6 

2720 

2713 

2706 

2699 

2692 

2686 

2679 

2672 

2665 

2659 

II7 

2652 

2645 

2638 

2632 

2625 

2618 

2612 

2605 

2598 

2592 

II8 

2585 

2579 

2572 

2566 

2559- 

2552 

2546 

2539 

2533 

2526 

II9 

2520 

2513 

2507 

2500 

2494 

24S8 

2481 

2475 

2468 

2462 

120 

2456 

2449 

2443 

2436 

2430 

2424 

2417 

2411 

2405 

2399 

I2I 

2392 

2386 

2380 

2374 

2367 

2361 

2355 

2349 

2342 

2336 

122 

2330 

2324 

2318 

2312 

2306 

2299 

2293 

2287 

2281 

2275 

123 

2269 

2263 

2257 

2251 

2245 

2239 

2233 

2227 

2221 

2215 

124 

2209 

2203 

2197 

2191 

2185 

2179 

2173 

2167 

2161 

2155 

125 

2149 

2143 

2138 

2132 

2126 

2120 

2114 

210S 

2102 

2097 

126 

2091 

2085 

2079 

2073 

2068 

2062 

2056 

2050 

2045 

2039 

127 

2033 

2028 

2022 

2016 

2011 

2005 

1999 

1994 

1988 

1982 

128 

1977 

1971 

1965 

i960 

1954 

1948 

1943 

1937 

1932 

1926 

I2Q 

1921 

1915 

1909 

1904 

1898 

1893 

1887 

1882 

1876 

1871 

130 

1865 

1S60 

1854 

1849 

1844 

1838 

1833 

1S27 

1822 

1816 

131 

1811 

1806 

1800 

1795 

1789 

1784 

1779 

1773 

1768 

1762 

132 

1757 

1752 

1746 

1741 

1736 

1730 

1725 

1720 

1715 

1709 

133 

1704 

1699 

1693 

16S8 

1683 

1678 

1672 

1667 

1662 

1657 

134 

1651 

1646 

1641 

1636 

1631 

1625 

1620 

1615 

1610 

1605 

135 

1599 

1594 

1589 

1584 

1579 

1574 

1569 

1564 

1558 

1553 

136 

1548 

1543 

1538 

1533 

1528 

1523 

1518 

1513 

1508 

1503 

137 

1498 

1493 

1488 

1483 

1477 

1472 

1467 

1462 

1457 

1453 

138 

1447 

1442 

1437 

1432 

1427 

1422 

1418 

1413 

1408 

1403 

139 

1398 

1393 

1388 

1383 

1378 

1373 

1368 

1363 

1358 

1353 

140 

1348 

1344 

1339 

1334 

1329 

1324 

1319 

1314 

1309 

1304 

141 

1300 

1295 

1290 

1285 

1280 

1275 

1270 

1266 

1261 

1256 

142 

1251 

1246 

1242 

1237 

1232 

1227 

1222 

1217 

1213 

1208 

143 

1203 

1198 

1193 

1189 

1184 

1179 

1174 

1170 

1165 

1160 

144 

1155 

1151 

1146 

1141 

1136 

1132 

1127 

1122 

1118 

1113 

145 

1108 

1103 

1099 

1094 

10S9 

1085 

1080 

1075 

1070 

1066 

146 

1061 

1056 

1052 

1047 

1042 

1038 

1033 

1028 

1024 

1019 

147 

1014 

lOIO 

1005 

lOOI 

996 

991 

987 

982 

977 

973 

148 

968 

963 

959 

954 

950 

945 

940 

936 

931 

927 

149 

922 

917 

913 

go8 

904 

899 

894 

8go 

885 

881 

101 


V. 

1 ® 

1 

2 

3 

4 

5 

6 

( 

8 

9 

F-s. 

1 Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

150 

876 

871 

867 

862 

858 

853 

849 

844 

840 

835 

I51 

830 

826 

821 

817 

8i2 

808 

803 

799 

794 

790 

152 

785 

781 

776 

771 

767 

762 

758 

753 

749 

744 

153 

740 

735 

731 

726 

722 

717 

713 

708 

704 

699 

154 

695 

690 

686 

681 

676 

672 

668 

663 

659 

654 

155 

650 

645 

641 

637 

632 

628 

623 

619 

614 

610 

156 

605 

601 

596 

592 

588 

583 

579 

574 

570 

565 

157 

561 

556 

552 

548 

543 

539 

534 

530 

523 

521 

158 

516 

512 

508 

503 

499 

494 

490 

4S6 

481 

477 

159 

472 

468 

464 

459 

455 

450 

446 

442 

437 

433 

160 

428 

424 

420 

415 

411 

406 

. 402 

398 

393 

389 

I6I 

385 

380 

376 

371 

367 

363 

358 

354 

350 

345 

162 

341 

337 

332 

328 

324 

319 

315 

310 

306 

302 

163 

297 

293 

289 

284 

280 

276 

271 

267 

263 

258 

164 

254 

250 

245 

241 

237 

232 

228 

224 

220 

215 

165 

2II 

207 

202 

198 

194 

189 

185 

181 

177 

172 

166 

168 

164 

160 

155 

151 

147 

142 

138 

134 

130 

167 

126 

I2I 

117 

113 

109 

104 

100 

96 

92 

88 

168 

83 

79 

75 

71 

67 

62 

58 

54 

50 

46 

169 

41 

37 

33 

29 

25 

21 

17 

12 

8 

4 

IX.  A GENERAL  TABLE  OE  VALUES  OF  -t 

w 

FOR  OGIVAL-HEADED  SHOT. 


Stars  (*)  indicate  that  the  unit  figure  is  to  he  taken  from  the  line  next  below. 


V. 

0 

1 

2 

h 

5 

6 

7 

8 

F-s. 

Seconds. 

1 Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

1 Secs. 

Secs. 

Secs. 

54 

22.078 

j* . q8o 

*.882 

*.688 

*.592 

*.496 

l*-40i 

*.306 

*.  212 

55 

21.118 

-025 

*•933 

*.841 

*-749 

*.658 

*•567 

i*-477 

*.388 

*•299 

56 

20.210 

1 . 122 

-034 

*-947 

*.860 

*•774 

*.688 

*.603 

*.518 

*-433 

57 

19-349 

.265 

.182 

-099 

.017 

*•935 

*•854 

*•773 

*.692 

*.612 

58 

18.532 

-453 

-374 

-295 

• 217 

.139 

.062 

*-985 

*.908 

*.832 

59 

17-756 

.681 

.606 

-531 

-457 

• 383 

• 309 

.236 

.163 

.091 

60 

17.019 

*-947 

*.876 

*.805 

*-734 

*.664 

*•594 

*•524 

*•455 

*.386 

61 

16.318 

-249 

.182 

.114 

-047 

*.980 

*.913 

*•847 

*.781 

*-715 

62 

15-650 

.585 

.520 

-456 

-392 

.328 

.265 

.201 

.139 

.076 

63 

15.014 

*.952 

*.890 

*.829 

*.768 

*.707 

*•647 

*.526 

*•467 

64 

14.407 

-348 

.290 

.231 

-173 

• 115 

.057 

'*.999 

*.942 

*•885 

65 

13.829 

-772 

.716 

.660 

.605 

• 549 

• 494 

•439 

•38s 

•330 

66 

13.276 

.222 

.168 

.115 

.062 

.009 

*.956 

*.904 

*.852 

*.800 

67 

12.748 

.696 

-645 

-594 

• 543 

•493 

• 442 

• 392 

-342 

.292 

68 

12.243 

.194 

.145 

.096 

• 047 

*•999 

*•950 

*.903 

*.855 

*.807 

69 

II . 760 

-713 

.666 

.619 

• 572 

.526 

.4S0 

•434 

.388 

•343 

70 

11.297 

.252 

.207 

.162 

.118 

•073 

.029 

*.985 

*.941 

*.893 

71 

10.854 

.811 

.768 

.725 

.682 

•639 

• 597 

• 555 

• 513 

•471 

102 


Y. 

« 1 

1 

2 

3 

4 

5 

« 1 

8 

9 

F-s. 

Seconds. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

72 

10.429 

.388 

-346 

.305 

.264 

.223 

.183 

. 142 

. 102 

.062 

73 

10.022 

*.982 

*.942 

*.903 

*.863 

*.824 

*.785 

*.746 

*.708 

*.669 

74 

9.631 

.592 

-554 

.516 

.478 

.441 

.403 

.366 

.329 

.292 

75 

9-255 

.218 

.182 

■ 145 

. 109 

• 073 

.037 

.oor 

*.965 

*.930 

76 

8.894 

.859 

.824 

.789 

.754 

.719 

.684 

.650 

.616 

.581 

77 

8.547 

-513 

.480 

.446 

.412 

-379 

.346 

.312 

.279 

.246 

73 

8.214 

.181 

. 148 

.116 

.084 

.052 

.020 

^.988 

*.956 

*.924 

79 

7-893 

.861 

.830 

-799 

.768 

-737 

.706 

.675 

-645 

.614 

80 

7-584 

- 553 

•523 

.493 

.463 

-453 

.404 

.374 

-345 

-315 

81 

7.286 

-257 

.228 

.199 

.170 

.141 

■ 113 

.084 

.056 

.027 

82 

6.999 

.971 

.943 

.915 

.887 

.859 

.832 

.804 

-777 

.750 

83 

6.722 

.695 

.668 

.641 

.615 

.588 

.561 

.535 

.508 

.482 

84 

6.456 

.430 

.404 

.378 

.352 

.326 

.300 

-275 

-249 

.224 

85 

6.198 

.173 

.148 

.123 

.098 

-073 

.048 

.024 

*-999 

*-974 

86 

5.950 

.926 

.901 

.877 

.853 

.829 

.805 

.781 

.757 

• 734 

87 

5.710 

.686 

.663 

.640 

.616 

-593 

.570 

.547 

-524 

.501 

88 

5.478 

• 455 

-433 

.410 

.388 

• 365 

-343 

.321 

.298 

.276 

89 

5-254 

.232 

.210 

.188 

.167 

.145 

.123 

. 102 

.080 

-059 

90 

5.038 

.016 

*.995 

*-974 

*■953 

*.932 

*.911 

*.890 

*.870 

*-849 

91 

4.829 

.808 

.788 

.768 

.747 

-727 

.707 

.687 

.667 

.648 

92 

4.628 

.608 

-589 

.569 

.550 

-531 

-5ir 

-492 

-473 

-454 

93 

4-435 

-417 

.398 

.379 

.361 

-342 

.324 

-305 

.287 

.269 

94 

4-251 

-233 

.215 

.197 

.179 

. I6I 

.144 

. 126 

. 109 

.091 

95 

4.074 

.057 

-039 

.022 

.005 

*.988 

*-971 

*-955 

*.938 

*.921 

96 

3-905 

.888 

.872 

.856 

■839 

.823 

.807 

.791 

.775 

-759 

97 

3-743 

. 728 

. 712 

.697 

.681 

.666 

.650 

.635 

.620 

.605 

98 

3-590 

.575 

.560 

-546 

.531 

.516 

.502 

-4S7 

•473 

-459 

99 

3-444 

• 430 

.416 

.402 

•389 

-375 

.361 

•347 

-334 

.320 

roo 

3.307 

.294 

.281 

.267 

.254 

.241 

.229 

.216 

.203 

. igo 

lOI 

3-178 

.165 

-153 

.141 

.12S 

.116 

.104 

.092 

.080 

.o6g 

102 

3-057 

-045 

.034 

.022 

.on 

*-999 

*.988 

*-977 

*.g66 

*-955 

103 

2.944 

-933 

.922 

.911 

.901 

.8go 

.880 

. 86g 

-859 

-849 

104 

2.839 

.829 

.819 

.809 

-799 

• 789 

.780 

.770 

.761 

-751 

105 

2.742 

.733 

.724 

•714 

-705 

.696 

.687 

.679 

.670 

.661 

106 

2.652 

.644 

.635 

.627 

.618 

.610 

.602 

-593 

.585 

-577 

107 

2.569 

.561 

.553 

-545 

-537 

.529 

.521 

-513 

.505 

.498 

loS 

2.490 

.482 

.475 

.467 

•459 

.452 

-444 

.437 

.430 

.422 

109 

2.415 

.407 

.400 

-393 

.386 

.378 

.371 

.364 

-357 

.350 

no 

2.343 

-336 

-329 

.321 

.314 

-307 

.301 

.294 

.287 

.280 

III 

2.273 

.266 

-259 

.252 

.246 

.239 

.232 

.225 

.219 

.212 

112 

2.205 

.199 

. 192 

.186 

-179 

.172 

. 166 

.159 

-153 

. 146 

113 

2.140 

.134 

.127 

. I2I 

.114 

. 108 

. 102 

-095 

.089 

.083 

114 

2.076 

.070 

.064 

.058 

.052 

.045 

-039 

.033 

.027 

.021 

115 

2.015 

.oog 

.003 

*-997 

*.991 

*-985 

*.979 

*-973 

*.967 

*.g6l 

116 

1-955 

-949 

-943 

-937 

•931 

.926 

.920 

.914 

.908 

.go2 

117 

1.897 

.891 

.885 

. .8S0 

.874 

.868 

.863 

.857 

.851 

.846 

118 

1.840 

-834 

.829 

.823 

.81S 

.812 

. 807 

.801 

.796 

.790 

119 

1-785 

-779 

.774 

.768 

.763 

.758 

-752 

.747 

.742 

•736 

103 


r 


^1 

0 

1 

2 

^ 1 

5 

6 1 

7 

8 

9 

F-s. 

Seconds. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

120 

1. 731 

.726 

.720 

-715 

.710 

.705 

.699 

-694 

.689 

.684 

I2I 

1.678 

-673 

.668 

.663 

.658 

-653 

.648 

.642 

.637 

.632 

122 

1.627 

.622 

.617 

.612 

.607 

.602 

-597 

.592 

-587 

.582 

123 

1-577 

-572 

.568 

-563 

-558 

-553 

-548 

-543 

-538 

-533 

124 

1.529 

• 524 

-519 

• 514 

-509 

-505 

.500 

-495 

.490 

.486 

125 

1.481 

.476 

.471 

.467 

.462 

-457 

-453 

.448 

-444 

-439 

126 

1-434 

-430 

-425 

.420 

.416 

.411 

.407 

.402 

-398 

-393 

127 

1.389 

-384 

-380 

-375 

-371 

.366 

.362 

-357 

-353 

-349 

128 

1-344 

-340 

-335 

-331 

-327 

.322 

.318 

•314, 

-309 

-305 

129 

1.301 

.296 

.292 

.288 

.284 

.279 

-275 

.271 

.267 

.262 

130 

1.258 

-254 

.250 

-245 

.241 

-237 

-233 

.229 

.225 

.220 

131 

1.216 

.212 

.208 

.204 

.200 

. 196 

. 192 

.18S 

.184 

.179 

132 

I-175 

.171 

.167 

-163 

.159 

-155 

-151 

.147 

-T43 

.139 

133 

I-135 

-131 

. 127 

.123 

.120 

.116 

.112 

. 108 

.104 

.100 

134 

1.096 

.092 

.088 

.084 

.081 

.077 

-073 

.069 

.065 

.061 

135 

1 .058 

-054 

.050 

.046 

.042 

-039 

-035 

.031 

.027 

.023 

136 

I .020 

.016 

.012 

-008 

.005 

.001 

*-997 

^=-994 

*.990 

*.986 

137 

0.982 

-979 

-975 

-971 

.968 

.964 

.961 

-957 

-953 

.950 

138 

.946 

.942 

-939 

•935 

-932 

.92S 

.924 

.921 

.917 

.914 

139 

.910 

.907 

-903 

.899 

.896 

.892 

.889 

.885 

.882 

.878 

140 

.875 

.871 

.868 

-864 

.861 

-857 

-854 

-850 

.847 

-843 

141 

.840 

.836 

-833 

-830 

.826 

.823 

.819 

.816 

.813 

. 809 

142 

.806 

.802 

-799 

-796 

.792 

-789 

-785 

. 782 

-779 

-775 

143 

.772 

.769 

-765 

.762 

-759 

-755 

-752 

-749 

• 745 

.742 

144 

-739 

-736 

-732 

.729 

.726 

.722 

.719 

.716 

-713 

.709 

145 

.706 

-703 

.700 

.696 

-693 

.690 

.687 

-683 

.6S0 

.677 

146 

•674 

.671 

.667 

.664 

.661 

.658 

-655 

.651 

.648 

.645 

147 

.642 

-639 

-636 

-632 

.629 

.626 

-623 

.620 

.617 

.614 

148 

.610 

.607 

.604 

.601 

-598 

-595 

-592 

-589 

.586 

-5S3 

149 

-579 

-576 

-573 

:570 

-567 

-564 

.56r 

-558 

• 555 

.552 

150 

-549 

.546 

-543 

-540 

-537 

-534 

-531 

.528 

-524 

-521 

151 

.518 

-515 

-512 

.509 

.506 

-503 

.500 

-497 

-494 

.491 

152 

.488 

-485 

.482 

.480 

-477 

-474 

-471 

.468 

.465 

.462 

153 

-459 

-456 

.453 

.450 

-447 

-444 

-441 

-438 

•435 

-432 

154 

.429 

.427 

.424 

.421 

.418 

-415 

.413 

.409 

.406 

-403 

155 

.400 

-398 

-395 

-392 

-389 

.386 

-383 

.3S0 

•377 

• 375 

156 

-372 

-369 

.366 

-363 

.360 

-358 

.355 

-352 

349 

-346 

157 

-343 

-341 

-338 

-335 

-332 

-329 

-326 

.324 

.321 

-318 

158 

-315 

.312 

.310 

-307 

-304 

.301 

.298 

.296 

-293 

.290 

159 

.287 

.285 

.282 

.279 

.276 

-274 

.271 

.268 

.265 

.263 

160 

.260 

-257 

-254 

-252 

-249 

.246 

-243 

.241 

.238 

-235 

161 

-232 

.230 

.227 

.224 

.222 

.219 

.216 

-214 

.211 

1 .20S 

162 

.205 

.203 

.200 

.197 

-195 

.192 

.189 

.1S7 

.184 

i . iSi 

163 

.179 

.176 

-173 

.171 

.168 

.165 

.163 

. 160 

-157 

1 -155 

164 

.152 

.150 

.147 

.144 

.142 

-139 

. 136 

-134 

-131 

.129 

165 

. 126 

.123 

. I2I 

.118 

.116 

-I13 

.110 

. 108 

.105 

-103 

166 

. 100 

.097 

-095 

.092 

.090 

.087 

.0S5 

.0S2 

.oSo 

-077 

167 

.075 

.072 

.070 

.067 

.064 

.062 

-059 

.057 

•O54 

.052 

168 

.049 

.047 

.044 

.042 

-039 

-037 

-034 

.032 

.029 

1 -027 

169 

.024 

.022 

.020 

.017 

.015 

;0I2 

.010 

.007 

-005 

.002 

lOi 


X.  A GEXEEAL  TABLE  OF  YALUES  OF  -s 

w 

FOB  SPHEEICAL  SHOT. 


Y. 

0 

1 

2 

1 

h 

5 

6 

7 

8 

9 

F-s. 

Feet. 

1 Feet 

Feet. 

Feet 

Feet 

Feet 

Feet. 

Feet 

Feet 

Feet 

50 

10649 

0620 

0592 

0563 

0535 

0506 

0478 

0450 

0422 

0394 

51 

10366. 

0338 

0310 

0283 

0255 

0228 

0201 

0174 

0147 

0120 

52 

10093 

0066 

0040 

0013 

*9987 

9961 

9935 

9909 

9883 

9857 

53 

9831 

9805 

9779 

9754 

9729 

9703 

9678 

9653 

9628 

9603 

54 

9578 

9553 

9529 

9504 

9480 

9455 

9431 

9407 

9383 

9359 

55 

9335 

9311 

9287 

9263 

9240 

9216 

9193 

9169 

9146 

9123 

56 

0100 

9077 

9054 

9031 

9008 

8986 

8963 

8941 

8918 

8896 

57 

8873 

8851 

8829 

8807 

8785 

8763 

8741 

8719 

8698 

8676 

58 

8655 

8633 

8612 

8591 

8569 

8548 

8527 

8506 

8485 

8464 

59 

8443 

8423 

8402 

8381 

8361 

8340 

8320 

8300 

8279 

8259 

60 

8239 

8219 

8199 

8179 

8159 

8139 

8120 

8100 

8081 

8061 

61 

8041 

8022 

8003 

7983 

7964 

7945 

7926 

7907 

7888 

7869 

62 

7850 

7832 

7813 

7794 

7776 

7757 

7739 

7720 

7702 

7683 

63 

7665 

7647 

7629 

7611 

7593 

7575 

7557 

7539 

7521 

7504 

64 

7486 

7468 

7451 

7433 

7416 

7398 

7381 

7364 

7346 

7329 

65 

7312 

7295 

7278 

7261 

7244 

7227 

7210 

7194 

7177 

7160 

66 

7144 

7127 

7110 

7094 

7078 

7061 

7045 

7029 

7012 

6996 

67 

6980 

6964 

6948 

6932 

6916 

6900 

6884 

6868 

6853 

6837 

68 

6821 

6806 

6790 

6775 

6759 

6744 

6728 

6713 

6698 

6682 

69 

6667 

6652 

6637 

6622 

6607 

6592 

6577 

6562 

6547 

6532 

70 

6517 

6503 

6488 

6473 

6459 

6444 

6430 

6415 

6401 

6386 

71 

6372 

6358 

6343 

6329 

6315 

6301 

6287 

6273 

6259 

6245 

72 

6231 

6217 

6203 

61S9 

6175 

6161 

6148 

6134 

6120 

6107 

73 

6093 

6079 

6066 

6052 

6039 

6026 

6012 

5999 

5986 

5972 

74 

5959 

5946 

5933 

5920 

5907 

5894 

5881 

5868 

5855 

5842 

75 

5829 

5816 

5803 

5790 

5778 

5765 

5752 

5740 

5727 

5714 

76 

5702 

5689 

s(^n 

5665 

5652 

5640 

5627 

5615 

5603 

5591 

77 

5578 

5566 

5554 

5542 

5530 

5518 

5506 

5494 

5482 

5470 

78 

5458 

5446 

5434 

5423 

5411 

5399 

5387 

5376 

5364 

5352 

79 

5341 

5329 

5318 

5306 

5295 

5283 

5272 

5260 

5249 

5238 

80 

5226 

5215 

5204 

5193 

5181 

5170 

5159 

5148 

5137 

5126 

81 

5115 

5104 

5093 

5082 

5071 

5000 

5049 

5038 

5027 

5017 

82 

5006 

4995 

4984 

4974 

4963 

4952 

4942 

4931 

4921 

4910 

83 

4900 

4889 

4879 

4868 

4858 

4847 

4837 

4827 

4817 

4806 

84 

4796 

4786 

4776 

4765 

4755 

4745 

4735 

4725 

4715 

4705 

85 

4695 

4685 

4(>75 

4665 

4655 

4645 

4635 

4625 

4615 

4605 

86 

4596 

4586 

4576 

4566 

4557 

4547 

4537 

4528 

4518 

4509 

87 

4499 

4490 

4480 

4471 

4461 

4452 

4442 

4433 

4423 

4414 

88 

4405 

4395 

4386 

4377 

4367 

4358 

4349 

4340 

4331 

4321 

89 

4312 

4303 

4294 

4285 

4276 

4267 

4258 

4249 

4240 

4231 

90 

4222 

4213 

4204 

4195 

4186 

4177 

4169 

4160 

4151 

4142 

91 

4134 

4125 

4116 

4107 

4099 

4090 

4081 

4073 

4064 

4056 

105 


V. 

0 

1 

2 

3 j 

* 

5 

6 

7 

8 

9 

F-s. 

Feet. 

Feot. 

Feet. 

Feet 

Feet. 

Feet 

Feet. 

Feet 

Feet. 

Feet. 

92 

4047 

4039 

4030 

4022 

4013 

4005 

3996 

3988 

3980 

3971 

93 

3963 

3954 

3946 

3938 

3930 

3921 

3913 

3905 

3897 

3888 

' 94 

3880 

3872 

3864 

3856 

3848 

3840 

3832 

3823 

■3815 

3807 

95 

3799 

3791 

3784 

3776 

3768 

3760 

3752 

3744 

3736 

3728 

96 

3721 

3713 

3705 

3697 

3689 

3682 

3674 

3666 

3659 

3631 

97 

3643 

3636 

3628 

3621 

3613 

3606 

3598 

3591 

3583 

3576 

98 

3568 

3561 

3553 

3546 

3539 

3531 

3524 

3516 

3509 

3502 

99 

3495 

3487 

3480 

3473 

3466 

3458 

3451 

3444 

3437 

3430 

100 

3423 

3416 

3409 

3402 

3395 

3388 

3381 

3374 

3367 

3360 

lor 

3353 

3346 

3339 

3332 

3325 

3319 

3312 

3305 

3298 

3291 

102 

3285 

3278 

3271 

3265 

3258 

3251 

3245 

3238 

3231 

3225 

103 

3218 

3212 

3205 

3199 

3192 

3186 

3179 

3173 

3166 

3160 

104 

3154 

3147 

3141 

3135 

3128 

3122 

3116 

3109 

3103 

3097 

105 

3091 

3084 

3078 

3072 

3066 

3060 

3054 

3048 

3041 

3035 

106 

3029 

3023 

3017 

3011 

3005 

2999 

2993 

2987 

2982 

2976 

107 

2970 

2964 

2958 

2952 

2946 

2941 

2935 

2929 

2923 

2918 

108 

2912 

2906 

2900 

2893 

2889 

2883 

2878 

2872 

2866 

2861 

109 

2855 

2850 

2844 

2838 

2833 

2827 

2822 

2816 

2811 

2805 

no 

2800 

2794 

2789 

2784 

2778 

^2773 

2767 

2762 

2757 

2751 

III 

2746 

2741 

2735 

2730 

2725 

2719 

2714 

2709 

2704 

2698 

II2 

2693 

2688 

2683 

2678 

2672 

2667 

2662 

2657 

2652 

2646 

113 

2641 

2636 

2631 

2626 

2621 

2616 

2611 

2606 

2601 

2596 

114 

2591 

2586 

2581 

2576 

2571 

2566 

2561 

2556 

2551 

2547 

115 

2541 

2536 

2531 

2526 

2522 

2517 

2512 

2507 

2502 

2497 

II6 

2492 

2487 

2483 

2478 

2473 

2468 

2464 

2459 

2454 

2449 

117 

2444 

2440 

2435 

2430 

2426 

2421 

2416 

2411 

2407 

2402 

118 

2397 

2393 

2388 

2383 

2379 

2374 

23C9 

2365 

2360 

2356 

1 19 

2351 

2346 

2342 

2337 

2333 

2328 

2323 

2319 

2314 

2310 

120 

2305 

2301 

2296 

2292 

22S7 

2283 

2278 

2274 

2269 

2265 

I2I 

2260 

2256 

2252 

2247 

2243 

2238 

2234 

! 2229 

2225 

2220 

122 

2216 

2212 

2207 

2203 

2199 

2194 

2190 

2185 

21S1 

2177 

123 

2172 

21C8 

2164 

2159 

2155 

2151 

2146 

; 2142 

2138 

2134 

124 

2129 

2125 

2121 

2116 

2112 

2108 

2104 

2099 

2095 

2091 

125 

2087 

2082 

2078 

2074 

2070 

2066 

2061 

2057 

2053 

2049 

126 

2045 

2040 

2036 

2032 

j 2028 

2024 

2020 

2015 

2011 

2007 

127 

2003 

1999 

1995 

1991 

19S6 

1982 

1978 

1974 

1970 

1966 

128 

1962 

1958 

1954 

1949 

1945 

1941 

1937 

1933 

1929 

1925 

129 

1921 

1917 

1913 

1909 

1905 

1901 

1897 

1893 

1SS9 

18S5 

130 

1881 

1877 

1873 

1869 

1 1865 

1S61 

1857 

1853 

1849 

1S45 

131 

1841 

1837 

1833 

1829 

1825 

1821 

1817 

1S13 

1S09 

1S06 

132 

i802 

1798 

1794 

1790 

17S6 

1782 

1778 

1774 

1770 

1766 

133 

1763 

1 1759 

1755 

1751 

1747 

1743 

1739 

1736 

1732 

172S 

134 

1724 

1720 

1716 

1713 

1709 

1705 

1701 

1697 

1694 

1690 

135 

1686 

16S2 

1678 

1675 

' 1671 

1667 

1663 

1660 

1656 

1652 

136 

1648 

1645 

1641 

1637 

1633 

1630 

1626 

1622 

161S 

1615 

137 

I6II 

1607 

1603 

1600 

1596 

1592 

1589 

1585 

1581 

1578 

133 

1574 

1570 

1567 

1563 

1559 

1556 

1552 

1548 

1545 

1541 

139 

1537 

1534 

1530 

1526 

: 1523 

1519 

1516 

1512 

1508 

1505 

140 

1501 

1497 

1494 

1490 

1487 

1483 

1479 

1476 

1472 

1469 

141 

1465 

|i46r 

1458 

1454 

1451 

1447 

1444 

1440 

1437 

1433 

106 


I 

I 


V. 

0 

1 

2 

3 

1 

5 

6 

i 

8 

9 

F-s. 

Feet. 

Feet 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet 

Feet. 

Feet. 

142 

1429 

1426 

1422 

1419 

1415 

14x2 

1408 

1405 

X4OI 

1398 

143 

1394 

1391 

1387 

1384 

1380 

1377 

1373 

1370 

1366 

1363 

144 

1359 

1356 

1352 

1349 

1345 

1342 

1338 

1335 

133X 

1328 

145 

1324 

1321 

1318 

1314 

1311 

1307 

1304 

1300 

1297 

1293 

146 

I2QO 

1287 

1283 

1280 

1276 

1273 

X270 

1266 

1263 

1259 

147 

1256 

1253 

1249 

1246 

1242 

1239 

1236 

1232 

X22g 

1225 

148 

1222 

12x9 

1215 

12X2 

1209 

1205 

1202 

1199 

1195 

1192 

149 

1189 

1185 

1182 

1179 

1175 

XX72 

1169 

1165 

1162 

1159 

150 

1155 

1152 

1149 

1145 

1142 

1139 

1135 

1132 

xx2g 

1126 

I51 

1122 

III9 

1 1 16 

IIT2 

1109 

1106 

1x03 

1099 

1096 

1093 

152 

1090 

1086 

1083 

1080 

1077 

1073 

XO7O 

1067 

1064 

1060 

153 

1057 

1053 

1051 

1047 

1044 

XO4X 

1038 

1034 

1031 

1028 

154 

1025 

1022 

1018 

1015 

1012 

1009 

1006 

X002 

999 

996 

155 

993 

990 

987 

983 

980 

977 

974 

971 

968 

964 

156 

961 

958 

955 

952 

949 

945 

942 

969 

936 

933 

157 

930 

9-7 

924 

920 

917 

914 

911 

908 

905 

go2 

153 

899 

895 

892 

889 

886 

883 

880 

877 

874 

871 

159 

868 

864 

861 

858 

855 

852 

849 

846 

843 

840 

160 

837 

834 

831 

828 

825 

822 

818 

8x5 

812 

8og 

I6I 

806 

803 

800 

797 

794 

791 

788 

785 

782 

779 

162 

776 

773 

770 

767 

764 

761 

75S 

755 

752 

749 

163 

746 

743 

740 

737 

734 

731 

728 

725 

722 

719 

164 

716 

713 

710 

707 

704 

701 

698 

695 

692 

689 

165 

686 

683 

6S0 

677 

674 

672 

66g 

666 

663 

660 

166 

657 

654 

651 

648 

645 

642 

639 

636 

633 

630 

167 

628 

625 

622 

619 

616 

613 

610 

607 

604 

601 

168 

598 

596 

593 

590 

587 

5S4 

581 

578 

575 

572 

l6g 

569 

567 

564 

561 

558 

555 

552 

549 

546 

544 

170 

541 

538 

535 

532 

529 

526 

524 

521 

518 

515 

171 

512 

509 

506 

504 

501 

498 

495 

492 

489 

487 

172 

484 

481 

478 

475 

472 

470 

467 

464 

461 

458 

173 

456 

453 

450 

447 

444 

442 

439 

436 

433 

430 

174 

428 

425 

422 

419 

416 

414 

411 

408 

405 

402 

175 

400 

397 

394 

391 

389 

386 

3S3 

380 

377 

375 

176 

372 

369 

366 

364 

361 

358 

355 

353 

350 

347 

177 

344 

342 

339 

336 

333 

33T 

328 

325 

322 

320 

173 

317 

314 

311 

309 

306 

303 

301 

298 

295 

292 

179 

290 

287 

284 

282 

279 

276 

273 

271 

268 

265 

180 

263 

260 

257 

255 

252 

249 

246 

244 

241 

238 

181 

236 

233 

230 

228 

225 

222 

220 

217 

214 

2X2 

182 

209 

206 

204 

201 

198 

196 

193 

igo 

188 

185 

183 

182 

180 

177 

174 

172 

169 

166 

164 

x6i 

158 

184 

156 

153 

150 

148 

145 

143 

X40 

137 

135 

132 

i8=i 

129 

127 

124 

122 

119 

xx6 

114 

XIX 

loS 

106 

186 

103 

XOI 

98 

95 

93 

90 

88 

85 

82 

80 

187 

77 

75 

72 

69 

67 

64 

62 

59 

57 

54 

188 

51 

49 

46 

44 

41 

39 

36 

33 

31 

28 

189 

26 

23 

21 

18 

15 

13 

xo 

7 

5 

3 

107 


XI.  A GENERAL  TABLE  OF  VALUES  OF  2^t 

w 

FOR  'SPHERICAL  SHOT. 


Stars  {*)  indicate  that  the  unit  figure  is  to  be  taken  from  the  line  next  below. 


V. 

0 

1 

2 

3 1 

5 

' 1 

8 

9 

F-s. 

Seconds. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs.  1 

Secs. 

Secs 

Secs. 

50 

13-414 

.356 

-299 

.242 

.185 

. 129 

-073 

.017 

*.962 

*.907 

51 

12.852 

-798 

-744 

.690 

-637 

-584 

-531 

-478 

.426 

-374 

52 

12.323 

.272 

.221 

. 170 

.119 

.069 

.020 

*.970 

*.921 

*.872 

53 

11.823 

-775 

.726 

-679 

.631 

-584 

-537 1 

.490 

-443 

-397 

54 

ir-351 

-305 

-259 

.214 

. 169 

.124 

.080  1 

.036 

*.991 

*-948 

55 

10.904 

.861 

.818 

-775 

-732 

.690 

-647 

.605 

-564 

.522 

56 

10.481 

.440 

-399 

-358 

-318 

.278 

.238 

.198 

.158 

.119 

57 

10.080 

.041 

.002 

*.964 

'='.926 

*.887 

*-849 

*812 

="-774 

*-737 

58 

9.700 

.663 

.626 

-589 

-553 

-517 

.481 

-445 

.409 

-374 

59 

9-338 

•303 

.268 

-234 

.199 

.165 

. 130 

.096 

.062 

.02Q 

60 

8-995 

.962 

-929 

-895 

.863 

.830 

-797 

-765 

-733 

.700 

61 

8.669 

-637 

.605 

-574 

.-542 

.511 

.480 

-449 

.419 

-388 

62 

8.358 

-327 

-297 

.267 

-237 

.208 

.178 

.149 

. 120 

.090 

63 

8.061 

-033 

.004 

*-975 

*-947 

*.919 

*.890 

*.862 

*-834 

*.807 

64 

7-779 

-752 

.724 

-697 

.670 

-643 

.616 

-5S9 

.562 

-536 

65 

7.510 

-483 

-457 

.431 

.405 

-379 

-354 

.328 

-303 

-277 

66 

7.252 

.227 

.202 

-177 

-153 

.128 

.103 

.079 

-055 

.030 

67 

7.006 

■••.982 

*-958 

*-935 

*.911 

*.887 

*.864 

*.841 

*.817 

*-794 

68 

6.771 

-748 

-725 

-703 

.680 

-657 

-635 

.613 

.590 

.568 

69 

6.546 

-524 

.502 

.481 

-459 

-437 

.416 

-394 

-373 

-352 

70 

6-331 

.310 

.289 

.268 

-247 

.227 

.206 

.185 

.165 

-145 

71 

6.124 

.104 

.084 

.064 

.044 

.025 

.005 

*-985 

*.966 

*.946 

72 

5-927 

-,907 

.888 

.869 

.850 

.831 

.812 

-793 

-774 

.756 

73 

5-/37 

.718 

. 700 

.681 

.663 

-645 

.627 

.609 

.591 

-573 

74 

5-555 

-537 

.519 

.502 

.484 

.466 

-449 

-432 

.414 

-397 

75 

5.380 

-363 

-346 

-329 

.312 

-295 

.278 

.261 

-245 

. 22S 

76 

5.212 

-195 

.179 

.163 

. 146 

. 130 

.114 

.098 

.0S2 

.066 

77 

5.050 

-034 

.019 

.003 

1^87 

*.972 

*.956 

*.941 

*.926 

*.gio 

78 

4-895 

.880 

.865 

-849 

-834 

.819 

.805 

.790 

• 775 

.760 

79 

4-745 

-731 

.716 

.702 

.687 

-673 

-659 

-644 

.630 

.616 

80 

4.602 

-587 

-573 

-559 

-545 

• 532 

.518 

.504 

.490 

-476 

81 

4-463 

-449 

-436 

.422 

.409 

-395 

.382 

-369 

-356 

-342 

82 

4-329 

.316 

-303 

.290 

-277 

.264 

•251 

-239 

.226 

.213 

83 

4.200 

.188 

-175 

. 163 

.150 

.138 

• 125 

-113 

.101 

.08S 

84 

4.076 

.064 

.052 

.040 

.028 

.oi6 

.004 

*.992 

*.980 

*.968 

85 

3-957 

•945 

• 933 

.921 

.910 

.898 

.887 

.875 

.864 

.852 

86 

3.841 

.829 

.818 

.807 

•796 

.784 

-773 

.762 

-751 

.740 

87 

3-729 

.718 

.707 

.696 

.685 

-675 

.664 

-653 

.642 

-632 

88 

3-621 

.611 

.600 

.590 

•579 

-569 

-558 

-548 

-537 

-527 

89 

3-517 

-507 

-496 

.486 

•476 

.466 

.456 

-446 

-436 

.426 

90 

3.416 

.406 

-396 

.386 

-377 

-367 

-357 

-347 

.33S 

.328 

91 

3-318 

-309 

-299 

.290 

.280 

I -271 

.261 

.252 

-243 

-233 

Y. 

0 

1 

2 

3 

4 

5 

6 

T 

8 

9 

F-s. 

Seconds. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

92 

3.224 

.215 

.206 

. 196 

.187 

.178 

. 169 

. 160 

• 151 

. 142 

93 

3-133 

.124 

.115 

. 106 

•097 

.088 

•079 

.071 

.062 

•053 

94 

3-044 

.036 

.027 

.OT9 

.010 

.001 

*-993 

*•984 

*.976 

*.967 

95 

2-959 

-95r» 

.942 

•934 

.926 

.919 

.909 

.901 

• 893 

.885 

96 

2.876 

.868 

.860 

.852 

•844 

• 836 

.828 

.820 

.812 

.804 

97 

2.797 

.789 

.781 

•773 

•765 

•758 

•750 

•742 

• 734 

•727 

98 

2.719 

.712 

• 704 

.697 

.689 

.682 

.674 

.667 

.659 

.652 

99 

2.645 

.637 

.630 

•623 

.616 

.608 

.601 

• 594 

• 587 

.580 

100 

2-572 

-565 

• 558 

•551 

•544 

• 537 

•530 

• 523 

• 517 

.510 

lOI 

2-503 

.496 

• 489 

.482 

.476 

.469 

.462 

.456 

•449 

•442 

102 

2.436 

.429 

•423 

.416 

.409 

•403 

•397 

•390 

•384 

•377 

103 

2-371 

.365 

• 358 

•352 

•346 

•339 

•333 

•327 

.321 

•315 

104 

2.308 

.302 

.296 

.290 

.284 

.278 

.272 

.266 

.260 

•254 

105 

2.248 

.242 

.236 

.231 

.225 

.219 

.213 

.207 

.202 

. 196 

106 

2.190 

. 184 

.179 

• 173 

. 167 

. 162 

• 156 

•151 

• 145 

. 140 

107 

2.134 

. 129 

.123 

.118 

.112 

.T07 

. 102 

.096 

.091 

.085 

108 

2.0S0 

.075 

.070 

.064 

•059 

•054 

•049 

•043 

•038 

•033 

109 

2.028 

.023 

.018 

•013 

.008 

•003 

*.998 

*•993 

*.988 

*.983 

no 

1.978 

-973 

.968 

•963 

• 958 

•953 

•948 

•943 

.938 

•933 

III 

1.929 

.924 

.919 

.914 

.910 

•905 

.900  1 .895 

.891 

.886 

II2 

1. 881 

.877 

.872 

.867 

.863 

•858 

•854 

•849 

•845 

.840 

113 

1-835 

.831 

.826 

.822 

.817 

.813 

808 

.804 

.800 

• 795 

1 14 

1. 791 

.786 

.782 

•778 

• 773 

.769 

.765 

.760 

• 756 

• 752 

115 

1-747 

-743 

•739 

•735 

• 730 

.726 

.722 

.718 

.714 

• 709 

II6 

1-705 

.701 

.697 

.693 

.689 

.684 

.680 

.676 

.672 

.668 

117 

1.664 

.660 

.656 

.652 

.648 

.644 

.640 

.636 

.632 

.628 

118 

1.624 

.620 

.616 

.612 

.608 

.604 

.600 

.596 

• 593 

• 589 

119 

1.585 

.581 

• 577 

•573 

• 569 

.566 

.562 

•558 

• 554 

.550 

120 

1-547 

.543 

•539 

•535 

• 532 

• 528 

• 524 

.520 

• 517 

• 513 

I2I 

1.509 

.506 

.502 

.498 

•495 

.491 

.487 

.484 

.480 

.476 

122 

1-473 

.469 

.466 

.462 

•459 

•455 

•451 

.448 

-444 

.441 

123 

1-437 

• 434 

• 430 

•427 

•423 

.420 

.416 

•413 

•409 

.406 

124 

1.402 

•399 

•395 

•392 

• 388 

•385 

.382 

•378 

•375 

• 371 

125 

1.368 

• 365 

.361 

•358 

• 355 

•351 

•348 

•344 

•341 

• 338 

126 

1-334 

• 331 

• 328 

•325 

.321 

•318 

•315 

• 311 

.308 

• 305 

127 

1.302 

.298 

• 295 

.292 

.289 

•285 

.282 

•279 

.276 

.272 

128 

1.269 

.266 

.263 

.260 

• 257 

•253 

.250 

• 247 

•244 

.241 

I2Q 

1.238 

• 234 

.231 

.228 

.225 

.222 

.219 

.216 

.213 

.210 

130 

1.206 

.203 

.200 

.197 

.194 

.191 

.188 

.185 

.182 

.179 

131 

1.176 

• T73 

.170 

.167 

. 164 

.161 

• 158 

• 155 

.152 

.149 

132 

1 . 146 

• 143 

. 140 

• 137 

• 134 

• 131 

. 128 

• 125 

. 122 

. 120 

133 

1.117 

.114 

.III 

. 108 

• 105 

. 102 

.099 

.096 

•093 

.091 

134 

1 .088 

.085 

.082 

•079 

.076 

•073 

.071 

.068 

.065 

.062 

135 

1.059 

-05^ 

•054 

•051 

.048 

•045 

.043 

.040 

•037 

•034 

136 

1.032 

.029 

.026 

.023 

-020 

.018 

•015 

.012 

.010 

.007 

137 

1.004 

.001 

*•999 

*.996 

*•993 

*.991 

*.988 

>.985 

*•983 

*.980 

138 

0.977 

•975 

•972 

.969 

.967 

.964 

.961 

•959 

.956 

•954 

139 

0.951 

.948 

.946 

•943 

• 940 

•938 

•935 

•933 

•930 

.927 

140 

0.925 

.922 

.920 

.917 

• 915 

.912 

•909 

•907 

• 904 

.902 

141 

0.899 

.897 

.894 

.892 

.889 

.867 

.884 

.882 

.879 

.877 

109 


V. 

0 

1 

2 

3 

4: 

5 

6 

7 

8 

9 

F-s. 

Seconds. 

1 Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

Secs. 

142 

0.874 

.872 

.869 

.867 

.864 

.862 

•859 

• 857 

• 854 

.852 

143 

0.849 

•847 

•844 

.842 

.839 

.837 

•835 

.832 

• 830 

.827 

144 

0. 825 

.822 

.820 

.818 

•815 

.813 

.810 

.808 

.806 

.803 

145 

0.801 

•798 

.796 

• 794 

•791 

• 789 

•787 

.784 

.782 

.780 

146 

0.777 

■775 

•773 

• 770 

.768 

. 766 

•763 

.761 

• 759 

.756 

147 

0.754 

■ 752 

•749 

• 747 

• 745 

.742 

•740 

•738 

• 736 

• 733 

148 

0.731 

.729 

•727 

• 724 

.722 

.720 

.717 

• 715 

• 713 

• 711 

149 

0.708 

. 706 

.704 

.702 

.700 

.697 

.695 

•693 

.691 

.688 

150 

0.686 

.684 

.682 

.680 

.677 

• 675 

•673 

.671 

.669 

.666 

151 

0.664 

.662 

.660 

.658 

.656 

•653 

.651 

.649 

.647 

.645 

152 

0.643 

.641 

•638 

•636 

•634 

.632 

.630 

.628 

.626 

.623 

153 

0.621 

.619 

.617 

.615 

.613 

.611 

.609 

.607 

•605 

.602 

154 

0.600 

.598 

.596 

• 594 

.592 

• 590 

.588 

.586 

• 584 

.582 

155 

0.580 

.578 

• 576 

• 574 

• 572 

• 570 

.568 

.565 

• 563 

.561 

156 

0.559 

.557 

•555 

• 553 

•551 

• 549 

•547 

• 545 

• 543 

.541 

157 

0.539 

.537 

• 535 

• 533 

• 531 

• 529 

•527 

• 525 

• 523 

.521 

158 

0.519 

• 517 

•515 

• 513 

• 511 

.510 

.508 

• 506 

.504 

.502 

159 

0.500 

.498 

.496 

•494 

•492 

.490 

.488 

.486 

•4S4 

.482 

160 

0.481 

•479 

•477 

•475 

•473 

•471 

.469 

.467 

.465 

• 463 

I6I 

0.462 

.460 

•458 

.456 

•454 

•452 

•450 

•448 

.446 

•445 

162 

0.443 

•441 

•439 

•437 

•435 

•433 

•432 

•430 

.428 

.426 

163 

0.424 

.422 

.421 

•419 

•417 

•415 

•413 

•411 

.410 

.408 

164 

0.406 

.404 

.402 

.401 

•399 

•397 

•395 

• 393 

• 392 

•390 

165 

0.388 

.386 

•384 

• 383 

•381 

.379 

•377 

• 375 

•374 

•372 

166 

0.370 

.368 

.367 

• 365 

•363 

.361 

.360 

•35S 

• 356 

•354 

167 

0.353 

• 351 

•349 

• 347 

•346 

.344 

•342 

•340 

• 339 

•337 

168 

0.335 

• 333 

•332 

.330 

.328 

• 327 

•325 

•323 

• 321 

.320 

i6g 

0.318 

.316 

•315 

•313 

•311 

.309 

• 30S 

.306 

• 304 

•303 

170 

0.301 

.299 

.298 

.296 

•294 

• 293 

.291 

. 289 

.288 

.286 

171 

0.284 

.283 

.281 

• 279 

.27S 

.276 

•274 

• 273 

•271 

.269 

172 

0.268 

.266 

. 264 

.263 

.261 

.260 

.258 

.256 

•255 

•253 

173 

0.251 

. 250 

.248 

• 247 

•245 

.243 

. 242 

.240 

.238 

•237 

174 

0.235 

• 234 

.232 

.230 

. 229 

.227 

.226 

.224 

.222 

.221 

175 

0.219 

.218 

.216 

.215 

.213 

.211 

.210 

CO 

0 

.207 

.205 

176 

0.203 

.202 

.200 

• 199 

• 197 

. 196 

• 194 

. 192 

.rgr 

. 1S9 

177 

0.  i88 

.i8-6 

'.185 

.183 

. 182 

. iSo 

■ 17S 

• 177 

.175 

• 174 

178 

0.  172 

• I/I 

. 169 

.168 

. 166 

.165 

. 163 

. 162 

. 160 

• 159 

179 

0.157 

• 156 

• 154 

• 152 

• 151 

.149 

. 148 

.146 

.145 

.143 

180 

0. 142 

.140 

• 139 

• 137 

.136 

•134 

• 133 

.131 

.130 

. 129 

181 

0.  127 

. 126 

• 124 

. 123 

. I2T 

. 120 

. iiS 

• 117 

.115 

• 114 

182 

0.  ri2 

.III 

. 109 

. io3 

.107 

.105 

• 104 

. 102 

. lOI 

.099 

183 

0.09S 

.096 

•095 

• 093 

.092 

.090 

.0S9 

.0S8 

.0S6 

.0S5 

184 

0.083 

.082 

.080 

• 079 

.078 

.076 

•075 

•073 

.072 

.070 

185 

0.069 

.06S 

.066 

.065 

.063 

.062 

,o6r 

•059 

.058 

•056 

186 

0.055 

• 054 

.052 

.051 

.049 

.04S 

• 047 

• 045 

.044 

.042 

187 

0.041 

.040 

.038 

• 037 

.035 

•034 

• 033 

•031 

.030 

.029 

188 

0.027 

.026 

.024 

• 023 

.022 

.020 

.019 

.018 

.oi6 

.015 

l8g 

0.014 

.012 

.Oil 

.009 

.008 

.007 

.005 

.004 

.003 

.001 

IIU 


XII.  TABLE  OF  VALUES  OF 
h = = 16.0954 FEET. 


t 

0 

1 

2 

3 

4 

5 

6 

T 

8 

9 

n 

Feet. 

Feet. 

Feet. 

Feet, 

Feet, 

Feet, 

Feet. 

Feet. 

Feet. 

Feet. 

I.O 

16.10 

16.42 

16.75 

17.0S 

17-41 

17-75 

18.08: 

18.43 

18.77 

19.12 

1. 1 

19.48 

19.83 

20.  19 

20.55 

20.92 

21.29 

21.66 

22.03 

22.41 

22.79 

1.2 

23.18 

23.57 

23.96 

24.35 

24-75 

25-15 

25-55 

25.96 

26.37 

26.78 

1-3 

27.20 

27.62 

28.04 

28.47 

28.90 

29-33 

29-77 

30.21 

30.65 

31.10 

1-4 

31.55 

32.00 

32.45 

32.91 

33-38 

33-84 

34.31 

34-78 

35-26 

35.73 

1-5 

36.21 

36.70 

37.19 

37.68 

38.17 

38.67 

39-17 

39.67 

40.18 

40.69 

1.6 

41.20 

41.72 

42.24 

42.76 

43.29 

43.82 

44.35 

44.89 

45.43 

45.97 

1-7 

46.52 

47.06 

47.62 

48.17 

48.73 

49.29 

49 . 86 

50.43 

51.00 

51-57 

1.8 

52.15 

52.73 

53.31 

53.90 

54-49 

55-09 

55.68 

56.28 

56.89 

57-49 

1. 9 

58.10 

58.72 

59.33 

59-95 

60.58 

61.20 

61.83 

62.46 

63.10 

63.74 

2.0 

64.38 

65.03 

65.68 

66.33 

66.98 

67-64 

68 . 30 

68.97 

69.64 

70.31 

2.1 

70.98 

71.66 

72.34 

73-02 

73-71 

74.40 

75-09 

75.79 

76.49 

77-20 

2.2 

77.90 

78.61 

79.32 

80.04 

80.76 

81.48 

82.21 

82.94 

83.67 

84.41 

2.3 

85.14 

85.89 

86.63 

87.38 

88.13 

88.89 

89.64 

90.41 

91-17 

91-94 

2.4 

92.71 

93.48 

94.26 

95.04 

95.83 

96.61 

97.40 

98.20 

98.99 

99-79 

2.5 

100.6  ] 

lOI  .4 

102.2 

103.0 

103.8 

104-7 

105.5 

106.3 

107.2 

108.0 

2.6 

108.8 

109.6 

no. 5 

111.3 

II2.2 

113-0 

113-9 

114-7 

115-6 

116.4 

2.7 

117.3 

118.2 

119. 1 

120.0 

120.8 

I21.7 

122.6 

123.5 

124.4 

125-3 

2.8 

126.2 

127.  I 

128.0 

128.9 

129.8 

130.7 

131-6 

132.6 

. 133.5 

134.4 

2.9 

135.4 

136.3 

137.2 

138.2 

139-1 

140.  I 

I4I  .0, 

142.0 

142.9 

143-9 

3-0 

144.9 

145.8 

146.8 

147.8 

148.8 

149-7 

150.7 

151-7 

152.7 

153-7 

3-1 

154.7 

155.7 

156.7 

157.7 

158.7 

159-7 

160.7 

161 . 7 

162.8 

163.8 

3-2 

164.8 

165.8 

166.9 

167-9 

169.0 

170.0 

171.1 

172. 1 

173.2 

174.2 

3-3 

175.3 

176.3 

177.4 

178.5 

179.6 

180.6 

181.7 

182.8 

183.9 

185  .0 

3-4 

186. 1 

187.2 

188.3 

189.4 

190.5 

191.6 

192.7 

193.8 

195.0 

196.1 

3-5 

197.2 

198.3 

199.4 

200.6 

201.7 

202.8 

204.0 

205.1 

206.3 

207.4 

3-6 

208.6 

209.7 

210.9 

212.  I 

213.3 

214-4 

215.6 

216.8 

218.0 

219.2 

3-i7 

220.3 

221.5 

222.7 

223.9 

225.1 

226.3 

227.5 

228. 8 

230.0 

231.2 

3.8 

232.4 

233.6 

234.9 

236.1 

237-3 

238.6 

239.8 

241.0 

242.3 

243.5 

3.9 

244.8 

246. 1 

247.3 

248.6 

249.9 

251.1 

252.4 

253-7 

255.0 

256.2 

4.0 

257.5 

258.8 

260. 1 

261 .4 

262.7 

264.0 

265.3 

266.6 

267.9 

269.2 

4.1 

270.6 

271.9 

273.2 

274.5 

275-9 

277.2 

278.5 

279.9 

281 . 2 

282.6 

4.2 

283.9 

285.3 

286.6 

288.0 

2S9.3 

290-7 

292.1 

293-5 

294.8 

296.2 

4.3 

297.6 

299,0 

300.4 

301.8 

303.2 

304.6 

306.0 

307.4 

308.8 

310.2 

4.4 

311.6 

313.0 

314.4 

315.9 

317-3 

318.7 

320.2 

321.6 

323-0 

324-5 

4.5 

325.9 

327.4 

328.8 

330.3 

331-8 

333-2 

334-7 

336.2 

337-6 

339-1 

4.6 

340.6 

342.1 

343.5 

345-0 

346.5 

348.0 

349-5 

351-0 

352.5 

354-0 

4.7 

355.6 

357.1 

358.6 

360. 1 

361.6 

363-2 

364-7 

366.2 

367.8 

369-3 

4.8 

370.8 

372.4 

373.9 

375-5 

377-1 

378.6 

380.2 

381.7 

383-3 

384.9 

4.9 

386.5 

388.0 

389.6 

391.2 

392.8 

394-4 

396.0 

397.6 

399-2 

400.8 

5-0 

402.4 

404.0 

405.6 

407.2 

408.8 

410.5 

412. i 

413.7 

415.3 

416.9 

‘1 

1 

2 

3 

4 

5 

6 

7 

8 

9 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

5-1 

418.6 

420.3 

421.9 

423-6 

425.2 

426.9 

428.5! 

430.2 

431-9 

433-5 

5-2 

435.2 

436.9 

438.6 

440-3" 

442.0 

443-6 

445.3' 

447.-0 

448.7 

450.4 

5-3 

452.1 

453-8 

455.5 

457-3 

458.9 

460.7 

462.4 

464.1 

465-9 

467-6 

5-4 

469.3 

471. 1 

472.8 

474-6, 

476.3 

478.1 

479.8 

481 .6 

483.4 

485.1 

5-5 

486.9 

488.6 

490.4 

492.2^ 

494.0 

495-8 

497-^ 

499-4 

501.2 

503.0 

5-6 

504.8 

506.6 

508.4 

510.2 

512.0 

513.8 

515-6 

517-5 

519-3 

521.1 

5-7 

522.9 

524.8 

526.6 

528.5* 

530.4 

532.2 

534-0 

535-8 

537.7 

539-6 

5-8 

541.4 

543.3 

545-2 

547-1 

549-0 

550.8 

552.7, 

554-6 

556.5 

558.4 

5-9 

560.3 

562.2 

564-1 

566.0 

567-9 

569.8 

571-7 

573-7 

575-6 

577*5 

6.0 

579.4 

581.4 

583-3 

585-2 

587.2 

589.1 

591 -I 

593-0 

595.0 

597.0 

6.1 

598.9 

600.9 

602.9 

604 . 8 . 

606.8 

608.8 

610.7 

612 . 7 

614.7 

616.7 

6.2 

618.7 

620.7 

622.7 

624.7 

626.7 

628.7 

630.7 

632.8 

634-8 

636.8 

6.3 

638.8 

640.9 

642.9 

644.9 

647.0 

649.0 

651.1 

653-1 

655.2 

657-  2 

6.4 

659-3 

661.3 

663.4 

665.5 

667.5 

669.6 

671 -7^ 

673-8 

675-9 

677.9 

6.5 

680.0 

682.1 

684.2 

686.3 

688.4 

690.5 

692.6 

694.8 

696.9 

699.0 

6.6 

701 . 1 

703.3 

705.4 

707.5 

709.7 

711.8 

713-9 

716.1 

718.2 

720.4 

6.7 

722.5 

724.7 

726.8 

729.0 

731-2 

733-4 

735-5 

737.7 

739-9 

742.1 

6.8 

744.3 

746.4 

748.6 

750. 8j 

753-0 

755-2 

757  - 5 

759-7 

761.9 

764.1 

6.9 

766.3 

■768.5 

770.8 

773.0] 

775-2 

777.4 

779-7 

781.9 

784.2 

786.4 

7.0 

788.7 

790.9 

793-2 

795-4'' 

797-7 

800.0 

802.3 

804.5 

806.8 

809. 1 

7-1 

811.4 

813-7 

816.0 

818.2 

820.5 

822.8 

825.1 

827.5 

829.8 

S32. 1 

7.2 

834.4 

836.7 

839.0 

841.3 

843-7 

846.0 

848.4 

850.7 

853.0 

855.4 

7.3 

857.7 

860. 1 

862.4 

864.8 

867.1 

869.5 

871.9! 

874-3 

876.6 

879.0 

7-4 

881.4 

883.8 

886.2 

888.5 

890.9 

893-3 

895.7 

898.1 

900.6 

903.0 

7-5 

905.4 

907.8 

910.2 

912.6 

915.1 

917-5 

919.9 

922.4 

924.8 

927.2 

7.6 

929.7 

932.1 

934-6 

937-0' 

939-5 

941.9 

944-4 

946.9 

949-3 

951.8 

7-7 

954.3 

956.8 

959-3 

961.8 

964.2 

966.7 

969.2. 

971-7 

974.2 

976.7 

7.8 

979.2 

981.8 

984-3 

986.8 

989-3 

991.8 

994  j 

996.9 

999-4 

1002 

7-9 

1005 

1007 

1009 

1012] 

1015 

1017 

1020 

1023 

1025 

1028 

8.0 

1030 

1033 

1035 

1038 

1041 

1043 

1046 

1048 

1051 

1053 

8.1 

1056 

1059 

1061 

1064 

1066 

1069 

1072 

1074 

1077 

loSo 

8.2 

1082 

1085 

1088 

1090'^ 

1093 

1095 

1098 

IIOI 

1104 

1106 

8.3 

1109 

1112 

1114 

1117^ 

1120 

1122 

1125 

II2S 

1130 

1133 

8.4 

1136 

1138 

1141 

1144 

1147 

1149 

1152 

1155 

1157 

ii6o 

8.5 

1163 

1166 

1158 

II7I 

1174 

1177 

1179 

IIS2 

1185 

liSS 

8.6 

1190 

1193 

1196 

1199 

1202 

1204 

1207 

1210 

1213 

1216 

8.7 

1218 

1221 

1224 

1227 

1230 

1232 

1235 

123S 

1241 

1244 

8.8 

1246 

1249 

1252 

1255 

1258 

1261 

1264 

1266 

1269 

1272 

8.9 

1275 

1278 

1281 

1284 

1286 

12S9 

1292 

1295 

129S 

1301 

9.0 

1304 

1307 

1310 

1*^12 

1315 

1318 

1321 

1324 

1327 

1330 

9.1 

1333 

1336 

1339 

1342 

1345 

1348 

1350 

1353 

1356 

1359 

9.2 

1362 

1365 

1368 

1371 

1374 

1377 

13S0 

1383 

13S6 

1389 

9-3 

1392 

1395 

1398 

1401 

1404 

1407 

1410 

1413 

1416 

1419 

9-4 

1422 

1425 

1428 

1431 

1434 

1437 

1449 

1444 

1447 

1450 

9-5 

1453 

1456 

1459 

1462 

1465 

146S 

1471 

1474 

1477 

14S0 

9.6 

1483 

i486 

1490 

1493 

1496 

1499 

1502* 

1505 

150S 

1511 

9-7 

1514 

1518 

1521 

1524 

1527 

1530 

1533 

1536 

1540 

1543 

9.8 

1546 

1549 

1552 

1555 

155S 

1562 

1565 

1568 

1571 

1574 

9-9 

1578 

1581 

1584 

1587 

1590 

1593 

1597 

1600 

1603 

1606 

112 


APPENDIX  II. 


TABLE  I. 


Densities  corresponding  to  different  values  of  — W'  -j-  w, 
in  grammes. 


Is  umbers. 

0 

1 

2 

3 

1 

5 

G 

T 

8 

9 

DifF. 

700 

r-93579 

551 

523 

496 

468 

1 

413 

385 

358 

330 

27.6 

701 

303 

275 

247 

220 

192 

165 

137 

109 

082 

054 

27.6 

702 

027 

997 

972 

944 

917 

890 

862 

835 

807 

7 So 

' 27.4 

703 

1-92753 

725 

698 

670 

643 

616 

588 

561 

533 

506 

27-4 

704 

479 

451 

424 

396 

369 

342 

314 

287 

259 

232 

27-4 

705 

205 

177 

150 

123 

096 

069 

041 

014 

987 

960 

27.2 

706 

1-91933 

905 

878 

851 

824 

797 

770 

743 

716 

6S9 

27.1 

707 

662 

634 

607 

580 

553 

526 

499 

472 

445 

418 

27.1 

708 

391 

364 

337 

310 

283 

256 

229 

202 

175 

148 

27.0 

709 

I2I 

094 

067 

040 

013 

986 

959 

932 

905 

878 

26.9 

710 

1.90852 

825 

798 

771 

744 

718 

691 

664 

637 

610 

26.8 

711 

584 

557 

530 

503 

476 

450 

423 

396 

369 

342 

26.8 

712 

316 

289 

262 

235 

209 

182 

155 

129 

102 

075 

26.7 

713 

049 

022 

995 

969 

942 

916 

889 

862 

836 

809 

26.6 

714- -...V... 

1.89783 

756 

730 

703 

677 

651 

624 

597 

571 

544 

26.5 

715 

518 

491 

465 

438 

412 

385 

359 

332 

306 

279 

26.5 

716 

253 

226 

200 

173 

147 

121 

094 

068 

041 

015 

26.4 

717 

I .88989 

962 

936 

910 

883 

857 

831 

804 

778 

752 

26.3 

718 

726 

699 

673 

647 

620 

594 

568 

541 

515 

489 

26.3 

719 

463 

436 

410 

384 

358 

332 

306 

280 

254 

228 

26.1 

720 

202 

175 

149 

123 

097 

071 

045 

019 

993 

967 

26.1 

721 

1.87941 

914 

888 

862 

836 

810 

784 

758 

732 

706 

26.1 

722 

680 

654 

628 

602 

576 

550 

524 

498 

472 

446 

25-9 

723 

421 

395 

369 

343 

317 

291 

265 

239 

213 

187 

25-9 

724 

162 

136 

no 

084 

058 

033 

007 

981 

955 

929 

25-8 

725 

I . 86904 

878 

852 

826 

800 

775 

749 

723 

697 

671 

25.8 

726 

646 

620 

594 

568 

543 

517 

491 

466 

440 

414 

25-7 

727 

389 

363 

337 

311 

286 

260 

234 

209 

183 

157 

25-7 

728 

133 

107 

082 

056 

031 

005 

9S0 

954. 

929 

893 

25.6 

729 

1.85878 

852 

827 

801 

776 

750 

725 

699 

674 

648 

25-5 

730 

623 

598 

573 

547 

522 

495 

471 

446 

420 

395 

25-4 

115 


Table  I. — Continued. 


Numbers. 

0 

1 

1 

2 

3 

4 

K 

0 

6 

7 

8 

9 

Diff. 

731 

1.85369 

344 

318 

293 

267 

243 

217 

192 

167 

142 

25-2 

732 

II6 

091 

066 

041 

015 

989 

973 

939 

^14 

8go 

24.9 

733 

I . 84863 

839 

813 

786 

762 

737 

714 

6S7 

653 

637 

25.7 

734 

612 

587 

562 

536 

511 

486 

461 

436 

411 

389 

25.0 

735 

361 

336 

311 

286 

260 

235 

210 

185 

150 

135 

25.0 

736 

no 

085 

060 

035 

010 

985 

960 

935 

910 

8S5 

25.0 

737 

1.83860 

835 

811 

786 

761 

736 

711 

685 

661 

636 

25.0 

738. 

612 

586 

560 

536 

510 

487 

461 

437 

412 

38S 

25.0 

739 

362 

338 

313 

288 

264 

239 

214 

189 

165 

140 

25.0 

740 

II4 

090 

064 

041 

016 

991 

967 

942 

917 

893 

25.0 

741 

1.82868 

843 

8lg 

794 

769 

745 

720 

695 

670 

645 

24.6 

742 

621 

596 

572 

547 

523 

49S 

474 

449 

425 

400 

24.5 

743 

376 

351 

326 

302 

277 

253 

228 

203 

179 

154 

24.6 

744 

130 

105 

081 

056 

032 

008 

983 

959 

934 

910 

24.6 

745 

I. 81886 

861 

837 

812 

78S 

764 

739 

715 

691 

666 

24.4 

746 

642 

617 

593 

569 

544 

520 

496 

471 

447 

423 

24.3 

747 

399 

374 

350 

326 

302 

278 

253 

22Q 

205 

iSi 

24.2 

748 

157 

132 

108 

084 

060 

036 

on 

987 

963 

939 

24.2 

749 

I . 80915 

890 

866 

842 

818 

794 

770 

746 

722 

69S 

24.1 

750 

674 

649 

625 

601 

577 

553 

529 

505 

48 1 

457 

24.1 

751 

433 

409 

385 

361 

337 

313 

289 

265 

241 

217 

24.0 

752 

193 

l6g 

145 

121 

097 

073 

049 

025 

001 

977 

24.0 

753 

1-79953 

929 

905 

881 

857 

833 

S09 

7S5 

761 

737 

23-9 

754 

714 

6go 

666 

642 

619 

595 

571 

54S 

524 

500 

23-7 

755 

477 

453 

429 

405 

382 

358 

334 

311 

2S7 

263 

23.7 

756 

240 

216 

192 

168 

145 

I2I 

097 

074 

050 

026 

23.7 

757 

003 

979 

955 

931 

go8 

S84 

S60 

837 

S13 

789 

23.7 

758 

1.78766 

742 

719 

695 

672 

648 

625 

601 

57S 

554 

23-5 

759 

531 

507 

484 

460 

437 

413 

390 

366 

343 

319 

23*5 

760 

296 

272 

249 

225 

202 

179 

155 

132 

loS 

085 

23.4 

761 

062 

039 

015 

992 

g6S 

945 

921 

89S 

^74 

851 

23*4 

762 

1.77828 

804 

781 

758 

734 

711 

6SS 

664 

641 

61S 

23.4 

763 

595 

571 

54S 

525 

502 

479 

455 

432 

409 

3S6 

23.2 

764 

363 

339 

316 

293 

270;  247 

223 

200 

177 

154 

2j).2 

765 

131 

107 

084 

061 

038 

015 

992 

969 

946 

923 

23.1 

766 

I . 76900 

876 

S53 

S30 

807 

J-7S4 

.3S 

. 715 
1 

692 

23.x 

116 


Table  I. — Continued. 


Numbers. 

0 

1 

2 

3 

1 

5 

6 

7 

8 

9 

Diff. 

767 

I . 76669 

646 

623 

600 

577 

554 

531 

508 

485 

462 

23.0 

768 

439 

416 

393 

370 

347 

324 

301 

278 

255 

232 

22.9 

769 

210 

187 

164 

141 

118 

095 

072 

049 

026 

003 

22.9 

770 

1.75981 

958 

935 

912 

889 

866 

843 

820 

797 

774 

22.9 

771 

752 

729 

706 

683 

661 

638 

615 

593 

570 

547 

22.7 

772 

525 

502 

479 

456 

434 

411 

3S8 

366 

343 

320 

22.7 

773 

298 

275 

252 

227 

207 

184 

161 

139 

II6 

093 

22.7 

774 

071 

048 

025 

003 

980 

958 

935 

912 

890 

867 

22.6 

775 

I • 74845 

822 

800 

777 

755 

732 

710 

6S7 

665 

642 

22 . 5 

776 

620 

597 

575 

552 

530 

507 

4S5 

463 

440 

418 

22.5 

777 

395 

372 

350 

327 

305 

283 

260 

238 

215 

193 

22.4 

778 

171 

148 

126 

104 

081 

059 

037 

014 

992 

970 

22.3 

779 

1-73948 

925 

903 

881 

858 

836 

814 

791 

769 

747 

22.3 

780 

725 

702 

680 

658 

635 

613 

591 

568 

546 

524 

22.3 

781 

502 

479 

457 

435 

413 

39X 

368 

346 

324 

302 

22.2 

782 

280 

257 

235 

213 

191 

169 

147 

125 

103 

081 

22.1 

783 

059 

036 

014 

992 

970 

948 

926 

W 

882 

860 

22.1 

784 

1.72838 

815 

793 

77X 

749 

729 

705 

683 

661 

639 

22.1 

785 

617 

595 

573 

551 

529 

507 

485 

463 

441 

419 

21.9 

786 

39S 

376 

354 

332 

310 

2S8 

266 

244 

222 

200 

21.9 

787 

X79 

X57 

135 

113 

091 

070 

048 

026 

004 

982 

21.8 

788 

I . 71961 

939 

917 

895 

873 

852 

830 

808 

786 

764 

21.8 

789 

743 

721 

699 

677 

656 

634 

612 

591 

569 

547 

21.7 

790 

526 

504 

482 

460 

439 

417 

395 

374 

352 

330 

21.7 

791 

309 

287 

265 

243 

222 

200 

178 

157 

135 

113 

21.7 

792 

092 

070 

049 

027 

006 

984 

963 

941 

920 

898 

21.5 

793 

1.70887 

855 

833 

812 

790 

769 

747 

725 

704 

682 

21.6 

794 

661 

639 

618 

596 

575 

554 

532 

511 

489 

46S 

21.4 

795 

447 

425 

404 

382 

361 

340 

318 

297 

275 

254 

21.4 

796 

233 

2II 

igo 

168 

147 

126 

104 

083 

061 

040 

21.4 

797 

019 

997 

976 

954 

933 

912 

890 

869 

847 

826 

21.3 

79S 

1.69806 

784 

763 

742 

721 

700 

679 

658 

639 

616 

21 . 1 

799 

595 

573 

552 

531 

509 

488 

467 

445 

424 

403 

21.2 

800 

382 

360 

339 

318 

297 

276 

254 

233 

212 

191 

21. 1 

801 

170 

149 

128 

107 

086 

065 

044 

023 

002 

981 

21.0 

802 

1.68959 

938 

917 

896 

875 

854 

8-33 

812 

791 

770 

21.0 

117 


Table  I. — Continned. 


N umbers. 

0 

1 

2 

3 

4 

5 

6 

7 

8 , [) 

DifF. 

803 

1.68749 

728 

707 

686 

665 

644 

623 

602 

581  560 

21.0 

804 

539 

518 

497 

476 

455 

434 

413 

392 

371,  350 

21.0 

805 

329 

308 

287 

266 

245 

224 

203 

182 

161  140 

20.9 

806 

120 

099 

078 

057 

036 

015 

994 

973 

952  932 

20.9 

807 

1.67912 

891 

870 

849 

828 

808 

787 

766 

745  724 

20.8 

808 

704 

683 

662 

641 

621 

600 

579 

559 

538,  517 

20.7 

809 

497 

476 

455 

434 

414 

393 

372 

352 

331  310 

20.7 

810 

290 

269 

248 

228 

207 

187 

166 

145 

125  104 

20.6 

811 

084 

063 

042 

022 

001 

981 

960 

939 

919  8g8 

20.6 

812 

1.66878 

857 

837 

816 

796 

775 

755 

734 

714'  693' 

20.5 

813 

673 

652 

632 

61I 

591 

570 

550 

529 

509  488, 

20.5 

814 

468 

447 

427 

406 

386 

366 

345 

325 

304|  284^ 

20.4 

815 

264 

243 

223 

203 

182 

162 

141 

I2I 

loi  oSo 

20.4 

816 

060 

039 

019 

999 

978 

958 

938 

917 

897  877^ 

20.3 

817 

1.65857 

836 

816 

796 

775 

755 

735 

714 

694'  674’ 

20.3 

818 

654 

633 

613 

593 

573 

553 

533 

512 

492  472 

20.2 

819 

452 

431 

411 

391 

371 

351 

330 

310 

290  27O; 

20.2 

820 

250 

229 

209 

189 

169 

149 

129 

109 

089  069 

20.  I 

821 

049 

028 

008 

988 

968 

948 

928 

go8 

8SSj  868 

20.1 

822 

1.64848 

828 

808 

788 

768 

748 

72S 

70S 

688  668 

20.0 

823 

648 

628 

608 

588 

568 

548 

528 

508 

488  46S 

20.0 

824 

448 

428 

408 

388 

368 

348 

328 

308 

288  268 

19.9 

825 

249 

229 

209 

189 

169 

149 

129 

109 

089  069 

19.9 

826 

050 

030 

010 

990 

970 

950 

930 

910 

890  870 

19.9 

827 

1.63851 

831 

811 

791 

771 

752 

732 

712 

692  672 

ig.S 

828 

653 

633 

613 

593 

574 

554 

534 

515 

495  475 

19.7 

829 

456 

436 

416 

396 

377 

357 

337 

318 

29S  27S 

19.7 

830 

259 

239 

219 

200 

180 

I61 

141 

I2I 

102  082 

19.6 

831 

063 

043 

023 

004 

984 

965 

945 

925 

go6  886 

19.6 

832 

1.62867 

847 

827 

808 

788 

769 

749 

729 

710  690 

19.6 

833 

671 

651 

632 

612 

593 

573 

554 

534 

515  495' 

19.5 

834 

476 

456 

437 

417 

398 

379 

359 

340 

320;  301 

19.4 

835 

282 

262 

243 

223 

204 

184 

165 

145 

126  106 

19.5 

836 

0S7 

067 

048;  029 

009 

990 

971 

951 

932  913 

19.3 

837 

I .61894 

874 

855 

836 

816 

797 

778 

758 

739  720 

19.3 

838 

701 

681 

662 

643 

623 

604 

585 

565 

546  527 

19.3 

118 


Table  I. — Continued. 


Numbers. 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

Dm. 

839 

1 .61508 

488 

469 

450 

431 

412 

392 

373 

354 

335 

19.2 

840. . . 

316 

296 

277 

258 

239 

220 

200 

181 

162 

143 

19.2 

841 

124 

104 

085 

066 

047 

028 

009 

990 

971 

952 

19.1 

842 

1.60933 

913 

894 

375 

856 

837 

817 

798 

779 

760 

19.2 

843 

741 

722 

703 

C84 

665 

645 

627 

608 

589 

570 

19,0 

844 

551 

532 

513 

494 

475 

456 

437 

418 

399 

380 

19.0 

845 

361 

342 

323 

304 

285 

266 

247 

228 

209 

igo 

18.9 

846 

172 

153 

134 

115 

096 

077 

058 

039 

020 

001 

19.0 

847 

1.59982 

963 

944 

925 

906 

888 

869 

850 

831 

812 

18.8 

848 

794 

775 

756 

737 

718 

700 

681 

662 

643 

624 

18.8 

849 

606 

587 

568 

549 

530 

512 

493 

474 

455 

436 

18.8 

850 

418 

399 

380 

361 

342 

324 

305 

286 

267 

248 

i8.8 

851 

230 

2II 

192 

174 

155 

137 

118 

099 

081 

062 

18.6 

852 

044 

025 

006 

987 

969 

950 

931 

913 

894 

875 

18.7 

853 

r. 58857 

838 

820 

801 

783 

764 

746 

727 

709 

690 

18.5 

854 

672 

653 

634 

615 

597 

578 

559 

541 

522 

503 

18.7 

855 

485 

466 

448 

429 

41 1 

392 

374 

356 

337 

319 

18.5 

856 

300 

281 

263 

244 

226 

208 

189 

171 

152 

134 

18.4 

857 

II6 

097 

079 

060 

042 

023 

005 

986 

968 

949 

18.5 

858 

I -57931 

912 

894 

875 

857 

839 

820 

802 

783 

765 

18.4 

859 

747 

728 

710 

692 

673 

655 

637 

618 

600 

582 

18.3 

860 

564 

545 

527 

509 

490 

472 

454 

435 

417 

399 

18.3 

861 

381 

362 

344 

326 

307 

289 

271 

252 

234 

216 

18.3 

862 

198 

179 

I6I 

143 

125 

107 

088 

070 

052 

034 

18.2 

863 

016 

997 

979 

961 

943 

925 

907 

889 

871 

853 

18. 1 

S64 

1.56835 

816 

798 

780 

762 

744 

725 

707 

68g 

671 

18.2 

865 

653 

634 

616 

598 

580 

562 

544 

526 

508 

490 

18. 1 

866 

472 

454 

436 

418 

400 

382 

364 

346 

328 

310 

18.0 

867 

292 

273 

255 

237 

2.19 

201 

183 

165 

147 

129 

18. 1 

868 

III 

093 

075 

057 

039 

021 

003 

985 

967 

949 

17.9 

869 

1-55932 

914 

896 

878 

860 

842 

824 

806 

788 

770 

17.9 

870 

753 

735 

717 

699 

681 

663 

645 

627 

609 

591 

17.9 

871 

574 

556 

538 

520 

502 

485 

467 

449 

431 

413 

17.8 

872 

396 

378 

360 

342 

324 

307 

289 

271 

253 

235 

17.8 

873 

218 

200 

182 

164 

146 

129 

III 

095 

075 

051 

17.8 

874 

040 

022 

004 

986 

969 

951 

933 

916 

898 

880 

17-7 

119 


Table  I. — Continued 


Is  umbers. 

0 

1 

2 

3 

4 

5 

6 

7 8 

9 

Diff. 

875 

I . 54863 

845 

827 

809 

792 

774 

756 

739  721 

703 

17-7 

876 

686 

668 

650 

633 

615 

598 

580 

562  545 

527 

17.6 

877 

510 

492 

474 

457 

439 

422 

404 

386  369 

351 

17.6 

878 

334 

r 

316 

298 

281 

263 

246 

228 

210,  193 

175 

17.6 

879 

158 

140 

123 

105 

083 

070 

052 

034  017 

999 

17.6 

880 

1.53982 

964 

947 

929 

912 

895 

877 

860  842 

825 

17-4 

881 

808 

790 

773 

755 

738 

721 

703 

686  668 

651 

17.4 

882 

634 

616 

599 

581 

564 

547 

529 

512  494 

477 

17.4 

883 

460 

442 

425 

407 

390 

373 

355 

338  320 

303 

17-4 

884 

286 

268 

251 

234 

216 

199 

182 

164  147 

130 

17-3 

885 

113 

095 

078 

061 

043 

026 

009 

991  974 

957 

17-3 

886 

I . 52940 

922 

905 

888 

871 

854 

836 

S19  802 

785 

17.2 

887 

768 

750 

733 

716 

699 

682 

664 

647  630 

613 

17.2 

888 

596 

578 

561 

544 

527 

510 

492 

475|  45S 

441, 

17.2 

889 

424 

406 

389 

372 

355 

338 

321 

304  287; 

270I 

17. 1 

8go 

253 

235 

218 

201 

1 84 

167 

150 

133  116 

099; 

17. 1 

891 

082 

064 

047 

030 

013 

996 

979 

962  945 

92S 

17.  I 

892 

1.51911 

894 

877 

860 

S43 

826 

809 

792  775 

758; 

17.0 

893 

741 

724 

707 

690 

673 

656 

639 

622  605 

588; 

16.9 

894 

572 

555 

53S 

521 

504 

487 

470 

453'  436 

419 

17.0 

895 

402 

3S5 

368 

351 

334 

317 

300 

2S3  266 

249 

16.9 

896 

233 

216 

199 

182 

165 

149 

132 

115  09S 

oSr 

i6.S 

897 

065 

048 

031 

0X4 

”^97 

981 

^64 

947[  930 

913 

16.8 

898 

1.50897 

880 

863 

S46 

S29 

813 

796 

779'  762 

745 

16.8 

899 

729 

712 

695 

678 

661 

645 

628 

611  594 

577 

16.8 

900 

561 

544 

527 

510 

494 

477 

460 

444  427 

41G 

16.7 

901 

394 

377 

360 

343 

327 

310 

293 

377,  260 

243 

16.7 

902 

227 

210 

193 

177 

160^  144 

127 

no  094 

077 

16.6 

903 

061 

044 

027 

Oil 

994!  97S 

944  92S 

911 

16.6 

904 

1.49895 

878 

862 

845 

829 

812 

796 

779  763 

746 

16.5 

905 

730 

713 

696 

6S0 

663 

647 

630 

613  597 

5 So 

16.6 

906 

564 

547 

531 

514 

498 

48 1 

465 

448  432 

415 

16.5 

907 

399 

3S2 

366 

349 

333 

317 

300 

2S4  267 

251 

16.4 

908 

235 

218 

202 

185 

169 

152 

136 

II9  103 

086 

16.5 

909 

070 

053 

037 

021 

OO-^ 

988 

^72 

955  939, 

923 

16.3 

910 

1.48907 

890 

857 

S4. 

825 

S09 

792  776 

760 

16.4 

120 


TABLE  II. 


Tdble  for  the  reduction  of  grammes  and  tenths  of  grammes 

to  grains. 

[From  700  grammes  to  910  grammes.] 


Numbers. 


0 


6 


9 


700. 

701. 

702. 

703- 

704. 

705. 

706. 
707- 

708. 

709. 

710. 

711. 

712. 

713 

714- 

715- 

716. 

717- 

718.. 

719. . 

720. . 

721. . 

722. . 

723-  • 

724. . 

725-  • 

726. . 

727. . 

728.. 

729. . 

730. . 


10801.00 

16.43 

31-9 

47-3 

62.7 

78.2 

93.6 
10909 . o 

24.4 

39- 9 
55-3 

70.7 

86.2 

1 1001 .6 

17.0 

32.5 

47-9 

63-3 

78.7 

94.2 

11109.6 

25.0 

40- 5 
55.9 
71-3 

86.8 

I 1202. 2 

17.6 

33.0 

48.5 

63-9 


02.5 

17.9 


04.1 

19.5 


05 .6  07.2  08 .740.3 


■ 8;i3-4 

22.6  24.1  25.7  27.2,28.8 

•7j44-3 

48.8  50.4I51.9  53.5  55.o's6.6  58.1,59-7 


33-435-0 


64.2 


95-1 

10.5 

25.9 

41.4 


96.7J98.2 
12. 1 13.6 

I 

27.5129.0 


79-7  81.3  82.8  84.4  85.9:87.5  89.0^90.6 

. 4 06 . o 

-8'2I.4 

.2^36.8  38.3 

43.044.5  46.1  47.649.2  50.7  52.3  53 


56.8  58.4(59.9  61. 


72.2 


87-7  89.3(90-8  92-4 


03.1 

18.5 

34-0 

49-4; 

64.8 

80.2 
95-7 

II . I 

26.5 
42.0 
57-4 

72.8 


36.5  38.1 


65 .8,67.3  68. 9 70.4  72.0 


99- 

15- 

30  632.133.7 


73-8175-3 


76 


04.7jo6.2 

20. 1(21 .6 

35-637-1 

5i-o'52.5 

66.4^67.9 


81.8 

97-3 

12.7 


83-3 

98.8 
14.2 

28.I|29.6 

43.6^45-1 

59.obo.5j62 
74-475-9  77- 


69 

84. 

00. 

15- 

31- 

46. 


88.3  89.9  9i.4'93.( 


03-7 

19. 1 
34-5 
50.0 

65-4 


05.3106.8  08 
20.7^22.3123. 
36.1 


73-5,75-1 


01.3  02.9 

i6.7'i8.3 


47-6(49-2 
5 63.oj64.6 
9 78.4I80.0 
93-9j95-5 

8 09.3^10.9 
4-7,26.3 

40.2j4i.8 
55-6;57-2 
71.0*72.6 

9 86.4188.0 

oi-9jo3-5 
17-3 18.9 

I 

-7i34-3 


14.9 

30.3 

45  - 8 

61.3 
76.6 
92.1 

07-5 

22.9 


.ij67.7  69.2 
5j83-i 
0,98.6 
4 T4.0 
8 29.4 
344.946.4 
7 60.3  61. ^ 


. I 75.7 


05.0 
20.4 
35-8 

48.3,49-9  51-4 

7 

I 


63.6  65.2 
79.0  80.6 
94-5^96-1 
09.9*11.5 

25.3  26.9 

40.7142.3 


37.6.39.; 

51.653.1  54. 756.2(57. s 

67.068.5.70.1  7i.6j73.2 


66. 

82. 

97- 

13- 

28. 

43- 

59- 

74- 


91. 1 
06.6 
22.0, 
37-4 
53-0 
68.3 

83-7 

6,99-2 

0^14.6 

4I30.0 


84.6 
00. 1 

15-5 

30.9 


77-2 

92.6 

08.1 

23-5 

38.9 

54-5 

69.8 

85-3 

00.7 

16.1 

31-5 


8(45.446.9 
3,60.9  62.4 

7176.3(77-8 


121 


Table  II. — Continued. 


Numbers. 

0 

1 

2 

3 

4 

0 

6 

7 8 

9 

731 

11279-3 

80.8  82.4L3.9  85.5 

87.0 

88.6 

1 

90.1  91.7 

93.2 

732. 

733-  . 

734-  ■ 

735- 
736. . 
737- 
738. 
739- 

740. 

741. 

742. 

743- 

744- 

745- 
746. 
747- 
748. 

749- 

750. 

751- 

752. 

753- 

754- 

755- 
756. 
757- 
758. 
759- 

760. 

761. 

762. 

763- 

764. 

765- 

766. 


94.8 
11310.2 

25.6 

41.0 

56.5 

71.9 

87-3 

11402.8 
18.2 

33- 6 

49.1 

64.5 
79-9 
95-4 

11510.8 

26.2 

41 .6 

57-1 

72.5 

87.9 

11603.4 

18.8 

34- 2 
49-7 

65.1 

80.5 

95-9 

11711.4 

26. 8 

42.2 
57-7 
73-1 

88.5 

11803.9 
19.4 


96.3197.9199.4  01 .0 02. 5 04. 1 05 .6  07.2  08.7 
II. 7 13.314.8  16.4  17.9  19.5  21.0  22.6  24.1 


27.1  28.7 

42.544.1 
58.0^59.6 
73-4j75-0 
88.890.4 
04-3|o5.9 
19.721.3 
35-1  36.7 
50.6)52.2 
66.0  67.6 
81.4)83.0 


30.2  31. 8|33- 3 34-9  36-4  38.039.5 

45.647.248.7  50.3  51.8^53-4  54-9 

I I I I I 

61. 1 62.7  64. 


76.5:78.1 
5 
o 

22.8  24.4 
38.2)39.8 
53.7|55.2 

69.1  70.7 

I 

84.5:86.1 


91.993. 

07.409. 


I96.998.5  00.001. 

Ill 

12.3.13.9  15.447. 

I27.7  29.3  30.8'32 

* I ^ ! 

43.1  44.746.247 

I I 

158.6  60.2  61 .7,63 

I I 1 I 

,74.075.677.1  78 

189.491.0*92.5  94 

I 1 

04.9  06.5  08.009 
|2o.32i.9'23.4  25 

135. 7'37. 3 38.8^40 

*5i.2'52.s'54.3  55 
1 i 1 

66.6  68.2  69.7  71 

82 .0^83 .6  85.1  86 

i I-  I- 

97.4'99.ooo.5  02 

12.9  14.5  16.0  17 


28.3 

43.7 

59.2 

74.6 

90.0 

05.4 


29.9'3I.4  33 
45.346.8^48 
60.8  62.3  63 

76.2  77.7  79 

91.693.1  94 
07.0*08.5  10 

I 

120.9  22.5  24.0  25 

i I I I 


2 65.8167.3  68.9  70.4 

79.6  81 .2:82.7  84.3  85.8 
tit'— 
95.0  96. 698. 1 99. 701. 2 

10.5  12. I I3.6'i5.2  16.7 
25.9  27.5  29.0  30.6  32.1 

41.342.944.446.047.5 
56.8  58.4  59.9  61.5  63.0 

72.2  73.8'75.3  76.9  78.4 

87. 6 89.2'90.7*92.3  93.8 
6 03. 1 04.7:06.2  07.8  09.3 
o 18.5  20.1  21.6  23.2  24.7 

.4  33.9  35.5  37.o'38.640.t 
.8  49.3  50. 9 52.4  54.0  55.5 
.3  64.8  66.4  67.9  69.5  71.0 
.7  80.2  81.8  S3. 3 84.9  86.4 
. I 95.6  97.2  98.7  00.3  01.8 
.611.1  12.7  14.2  i^.S  17.3 

I 

.0  26.5  28. 1 29.6  31.2  32.7 
.441.943.545-046.648.1 
■9  57-V59-ot6o.5  62.1  63.6 
.3*72.8  74.4  75.9  77.5  79.0 
.788.289.891.392.994.4 
. i'o3.6  05 .2  06. 7 0S.3  09.8 
.6  19.  i'20. 7 22.2  23.8  25.3 

.0  34.5  36.1  37-6  39-2  40.7 

.449.951.5  53.054.656.1 

.965.467.068.5  70.1  71.6 

.3  80.8  82. 4 83.9  85.5  87.0 

I I _i_ 

. 7 96 . 2 97 . 8 99 . 3 00 . 9 02 . 4 

.1  II. 6 13.2  14.7  16.3  17. 8 

.6  27.1  28.7  30.2  31.8  33.3 


122 


Table  II. — Continued. 


N umbers. 


767. 

768. 

769. 

770. 
771- 
772. 

773- 

774- 

775- 
776. 
777- 
778. 

779- 

780. 

7S1. 

782. 

783. 

784. 

785. 

786. 

787. 

788. 

789. 

790. 

791. 

792. 

793- 

794- 

795- 

796. 

797- 

798. 

799- 

800. 

801. 

802. 


2 ! 3 


11834.8 

50.2 

65.7 

81. 1 

96- 5 

11911.9 
27.4 

42.8 
58.25 
73.68 

89. 1 

12004.5 

19.9 
35-4 
50.8 

66.3 

81.7 

97.1 

12112.6 

28.0 

43-4 

58.8 
74-3 
89.7 

12205 . 1 

20.6 

36.0 

51-4 

66.9 

82.3 

97- 7 

12313.1 
28.6 

44.0 
59-4 
74-9 


36-3  37- 
51-7  53- 

67.2  68. 

I 

82.6  84. 

I 

98 .0  99 
13-4  15 
28.9  30 

I 

44-3  45 
59-8|6i 
75.276 

90.6  92 

07 
23 
38 
53 
69 

84 

00 

15 


4 ! 5 


C 


i 9 


I 

9 39-4  41 -042. 5 44- 1 45 -6  47 -2  48. 7 

I ' I I 

3 54.8  56.4  57.959.5  61.062.664.1 

I ! ! I 

8 70.3  71.9  73.475.0  76.5  78.1  79.6 
I i : I ' I I 

2 85.7  87.3  88.890.491.993.5  95.0 

6 01  . I 02. 7 04.2  05 .8  07.3  oS.9'10.4 

i ^ ' o ‘ a'  ! i I o 

o 16. 5 i8. 1 19.6  21 .2  22. 7 24.3  25 .8 

5 32  0 33.6'35.i  36.7^38.2'39.84i.3 

’ I ' ' i A 

947.449.0  50.5  52.1  53-6  55-2  56.7 


06.0 
21  .4 

36.9 
‘52.3 
,67.8 
|83.2 
'98.6 

14. 1 
29-5'3i 
44.946 

60.3  61 

'75.8  77 

I 

91 . 2 92 

06.6  08 

22.1  23 

37-5  39 

52.9  54 

68.4  70 

83.s'85 

99 . 2 00 . 

14.6  16. 


4 62 . 

8'78 
2'93 
6'og 

o 24.576.1  27.6 

5'40.04I.643.i 


.3  79.981.4 

.7  95.3  96.8 
I I 

. I 10.7  12.2 


.9  55- 
■ 4'70. 
.8  86. 


2 01.7 

I 

7 17-2 


57-058.5 

72.5  74.0 
87.989.4 


03.3  04. 
18.8  20. 


83.0  84.5  86 


98.499.9 

i3-7'i5-3 

29.2  30.7 

44.746.2 

60.  i'6i  .6 

75-6j77-i 

91.092.5 


06.407.9 

21.9  23.4 


772.2 

i'87.6 


01.5  03.0 
16.948.4 
32. 

47- 

63- 

78. 

94- 


777. 3^8. 840, 
I 52.7  54.2  55 


. I 32.6  34.2  35. 

.5  48.049.6  51. 

.9  63.4  65.0  66. 

.4  78.9  80.5  82.  o' 83. 6^85. 1 |s6 

•8'94-395-9  97-4  99-0^do.5*02 


8 

5'68.  i!69.6  71 .2 

7 

I 

2 09. 7|  1 1. 342. 8 14. 4' 15. 9^7. 5 

3 29.9*3i.4'35.o 

7 45. 3^46. 9^48. 5 
‘ I I ! i I 

• 5 56.0  57.6  59. 1 bo.  7 62.2  63.8 


I ■ . . 

7 25 .2  26.8  28. 
I 40.642.2  43. 


I < Al  A ■ 

071.5  73.1  74.6  76.2  77.979 


• J 

4 86.9’8S  . 5|go.ol9i  .6  93.  i'94. 7 
4'o7.oo8.5  jo.i 


8 02.3  03.905. 

I I ! 

2 17.7,19.3  20. 


8,22.4:23.9  25 

30.131.7  33.2  34.8  36.3’37.9'39.4  4I 

I II  I I 

45-5  47-1  48.6  50.2  5I-7  53-3  54-8  56 

60.9  62.5  64.0  65 .6  67. 1 68. 7|7o. 2 71 


-3:33-8 
849-3 
2j64-7 
7I80.2 
1I95-6 
541-0 
! , 

0|26.5 

441-9 

57-3 

72.7 

88.2 
03.6 

19.0 
34-5 

50.0 

65-3 

80.8 

96.2 

II  .6 

5 27-0 
042.5 
4 57-9 

8:73-3 


76.448.0,79.5  81.1,82.6,84.2  85.7,87.3  88.8 


1 I 


123 


Tabi.e  II. — Contmv.ed. 


Numbers.  j 

0 

1 : 2 : 3 4 ^ 5 6 : T ; 8 : 9 

1 

803 

12390.3 

1 ' ' ’ ' 

91.8  93.4  94.9  96.5  gS.o  99.6  01. 1 02.7  04. 

Sou 

12405.7 

07.208.8 10.3 1 1. 9 13.4 15.0 16.5 18. 1 19. 

805 

21 .2 

22.7  24.3  25.8  27.4  28.9  30.5  32.033.6  35. 

806 

36.6 

38. 139. 7 41.242.8^44.3  45.947.449.0  50. 

807 

52.0 

53.5  55.1 56.6  58.2  59.7  61.3  62.8  64.465. 

808 

67.4 

68.9^70.5^72.073.6  75.1 76.7  78.2  79.8  81. 

8og 

82.9 

84.4  86.0  87. 5 89. 1 90.6  92.2  93.7  95 .3  96. 

810 

98-3 

99.801.402.904.5  06^007.609.1 10.7 12. 

8II 

12513-7 

15.2  16. S|i8. 3' 19. 9 21.4  23. 0 24. 5 26.1  27. 

812 

^29.2 

30.7  32.3  33.8  35.436.938.5  40.041.643. 

813 

44.6 

46.1  47.7'49.2|5o.8  52.3  53-9  55-4  57 -O  58. 

814 

60.0 

61.5  63.i'64.6  66.2  67.7  69.3  70.8  72.4  73. 

815 

75  ■ 5 

77.0  78.6  80.1  81.7  83.2  84.8  86.3  87.9  89. 

816 

90.9 

92.4^94.0  95.5  97.1  98. 6 00. 2 01. 7 03. 3 04. 

817 

12606.3 

07.809.4  10.9  12.5  14.0  15.6  17. 1 18.7  20. 

818 

21 .7 

23.2  24.8  26.3  27.9  29.4  31.0  32.5  34.  T 35. 

819 

37-2 

38. 740.3  41. 8^3-4  44- 9 46 -5  48.049.6  51. 

820 

52.6 

54-1J55-7  57- 2I58.S  60.3  61 .9  63.465.066. 

821 

0 

00 

0 

69.5  71.1^72.6  74.2  75.7  77.3  -8.8  So. 4 Si. 

822 

83-5 

85.0  86.6  88.1  89.7  91 .2  92.8  94.3  95.9  97. 

823 

98.9 

00.4  02.0  03.5  05.1  06.6  oS  .2  09.7  II  .3  12 

824 

12714-3 

15 .817.4  iS  .9  20. 5 22.0  23.6  25 . 1 26.7  28 

825 

29.7 

31.2  32.8  34.3  35.9  37.439.040.5  42.143 

826 

45-2 

46.7'48.3  49.8  51.4  52.9  54.5  56.057.6  59 

827 

60.6 

62.1  63.7  65.2  66.8  68. 3 69.9  71-4  73-0  74 

828 

76.0 

77-579-1  80.6  82.2  83.7  85.3  86.8  SS.4  89 

829 

91.5 

93 . 0^94 . 6g6 . 1 '97 . 7 99 . 2 00 . 8 02 . 3 03 . 9 05 

830 

12806.9 

oS.4|io.o^i.5^i3.i  14.6  16.2  17.7  19.3  20 

831 

22.3 

'23.8  25.4  26.9128.5  30.031.6  33-1  34-7  36 

832 

37-8 

:39.3  40.9  42.4|44-oj45.5'47-i  48-6  50.2  51 

833 

53-2 

54-7  56-3  57-8  59-460.962.5  64.065.667 

834 

1 68.6 

70.171.7  73.2  74.8  76.3  77.9  79. 481. 0S2 

835 

! 84.1 

85.6'87.2  88.790-3  91-8  93-4  94-996-5  98 

836 

' 99-5 

01.002.6  04.1  05.7  07.2  08.8  10.3  1 1. 9 13 

837 

12914.9 

a6.4  18.0  19.5  21. 1 22.624.2  25.7  27.3  28 

838 

1 30-3 

3T-8!33-4  34-9  36.5  38.039.641.1  42.7  44 
1 1 i 1 ; 1 1 1 1 

12i 


Table  II. — Continued. 


Numbers. 


839- 

840. 

841. 

842. 

843. 

844. 

845. 

846. 

847. 

848. 

849. 

850. 

851. 

852. 

853- 

854- 

855. 

856. 

857. 

858. 
859- 

860. 

861. 

862. 

863. 

864. 

865. 

866. 

867. 

868. 

869. 

870. 

871. 

872. 

873- 

874. 


0 

1 

2 

3 

12945.8 

61.2 

76.6 

92.1 
13007.5 

22.9 

38.4 

53.8 

69.2 

84.6 

13100. 1 

15-5 

30.9 

46.4 

61.8 

77.2 

92.7 

13208.1 

23.5 

38.9 

54- 4 

69.8 

85.2 

13300.7 

16. 1 

31-5 

46.9 

62.4 

77.8 

93-2 

13405.7 

24.1 

39-5 

55- 0 

70.4 

85.8 


3 48.9  50.4  52.o'53.5 
7 64.3  65.8^67.4168.9 
I 79.7  81.2  82.8:84.3 

: I 1 

695. 296. 798. 3^99. 
o 10.6  12.1  13.7  15.2 


.4  26.0  27. 5 29. 1 


.941-5  43-0 
56.9  58.4 
72-3  73-8 
87.7  89.2 
03.2  04.7 
18.6  20. I 

34-035-5 

49-5  51-0 


44.6 

60.0 

75-4 

90.8 

06.3 

2I''.  7 

37-1 


30.6 

46.1 
61.5 
76.9 

92-3 

07.8 

23.2 
38-6 


52-6  54.1 

64.9  66.4  68.0^69.5 

80.3  81 .8183.4  84.9 
1 I I- 
95-8  97.3  98.900.4 

I 

II. 2 12.7  14.3  15. 8 


8 i 9 


55.1 56.655.2  59.7 

70. 572. 073-6, 75-1 

85.9  87. 4 89. 090. 5 
01 .4  02.9  04. 5 06.0 
16.8  18.3  19.9  21 .4 

32. 2 33. 7^35-3  36. 8 


47.749.2 
63.1^64.6 
78.5  80.0 

93-9  95-4 

09.4  10.9 
24.8  26.3 
40.241.7 
55-7'57-2 
71 .1  72.6 

86.5  88.0 

02.003.5 
17.4^18.9 


50.8  52.3 
66.2  67.7 
81 .6  83 . 1 

97.098.5 

12.5  14.0 

27-gj29-4 

43-3  44-8 

58-8|6o.3 

74-275-7 

I 

89. 6^91. 1 

L 

05.1  06.6 

! 

20.5  22.0 


3 
7 

I 

,6 
,0 
■4 
■9 
■3 
7 
.2 
.6 

.0  26. 6; 28. 1, 297 7131. 2 32.8:34.3  35-9  37-4 

! I I c o I i I Q 

•442-043.5  45.1 46.6^48.2  49.7  51.3  52.8 

■ 9 57-5  59-060.6  62.1163.7  65. 2^66. S|68. 3 

: I : I I 

,3  72.9  74.4  76.0:77.5  79.1  80.6  82.2  83.7 
: : ' : : 1 
7 88.3  89.8  91.4^92.9  94.5  96.0  97.6  99.1 

,2  03.8  05 .3  06.9  08.4  10. o II . 5 13. 1 14.6 
' ; I I I : 1 

.6  19.2  20.7  22.3  23.8  25.4  26.9  28.5  30.0 

,0*34.6  36.1  37.7'39.2'40.s|42.3  43.9j45.4 

.4  50.0  5i.5'53.i'54.6|56.2  57-7,59-3  60.8 

.9  65.5'67.o68.6  70.i'7i.7  73.2  74.8,76.3 
I I ' I I I 
,3  80.9  82.4  84.0  85 . 5 87. 1 88.6  90.2  91 . 7 

i , I o'  i-  !-  I-  i-  c - 

7:96.3  97.8  99.4  00.9  02.5  04.005.6  07.1 

,2  II. 8 13.3  14.9  16.4  18.019.5  21. I 22.6 
,6  27.228.7^30.3  3i.sj33.4'34.9  36.5  38.0 
,042.644.1  45.7  47.2  48.8  50.3  51.9  53.4 
,5  58.1  59.6  61.2  62.7  64.3  65.8  67.4  68.9 
•9  73-5  75-0  76.6  78.1  79.7  81.2  82.8  84.3 

,4  89.0  90.5  92.1  93.6  95.2  96.7  98.3  99.8 

i I ! I I I I 


125 


Table  II. — Continued. 


Numbers. 


875. 

876. 

877. 

878. 

879. 

880. 

881. 

882. 

883. 

884. 

885. 

886. 

887. 

888. 

889. 

890. 
8gi. 
892. 

893- 

894. 

895- 

896. 

897. 

898. 

899. 

900. 

901 . 

902. 

903. 

904. 

905. 

906. 

907. 
go8 
909, 
910 


0 

1 

2 

3 

•i  5 

CO 

0 

I350I.2 

16.7 

02.7 

18.2 

04.3 

a 

19.8 

05.8  07.408.9  10.5  L2.0 
21 .3  22.9  24.4  26.0  27. 5 

13-6 15. 1 

29.1  30.6 

32.1 

47-5 

63.0 

78.4 
93-8 

13609.3 

24.7 

40. 1 
55-6 

71.0 

86.4 

13701.8 
17-3 

32.7 

48.1 

63.6 
79-0 

94.4 

13809.9 
25-3 

40.7 

56.1 

71 .6 
87.0 

13902.4 
17.9 
33-3 

48.7 

64.2 
79.6 
95-0 

14010.4 
25-9 

41.3 


33-6  35 -2, 36- 7 38.3  39-8  41 -4'42. 9 44- 5 46-0 
49.o;5o.6’52.i  53-7  55-2  56.8  58.3  59.961.4 

I , I 

64.5  66.1  67.6  69.2  70.7  72.3  73.8  75.4  76.9 
79.9  81 . 5 83.0  84.6  86. 1 87.7  89.2  go. 8 92.3 
95-3 

10.8 

26.2  27 
41-6  43-2 
57-1  58.7 

72.5  74-1 

87.9 
03-3 
18.8 

34.2 


96.9  98.4  00. obi . 5 03. 1 04.6  06.2  07. 7 

12. 4' 13. 9 15. 5 17.0  18. 6 20. 1 21. 7 23. 2 

I C A 

29.3  30.9  32.4  34-035-5  37-1  38.6 

44.-746. 3 47-8  49-4|5o. 952-5  54-0 

60.2  61 .8  63.3  64.9  66.4  68.0  69.5 

75.6  77.278.7  80.3  81.8  83.4^84.9 

89.5  91.0  92.6  94.1  95.7  97.2  98.8  00.3 

04.g'06.4  08.0  09.5  II. I 12.6  14.2  15.7 

20.4  21 .9  23.5  25 .0  26.6  28. 1 29.7  31.2 

35-8  37-3  38.940.442.043.5  45.1  46.6 

49.6'5I.2'52.7'54.3  55.8  57.4  58.9’6o.5'62.o 

65.i|66.7|68.2  69.8  71.3  72.9  74.4  76.0  77.5 

80.5  82. 1 S3. 6 85 .2  86.7  88 .3  89.8  91 .4  92.9 

95 . 9 97 . 5 99 . o 00 . 6 02 . 1 03 . 7 05 . 2 06 . 8 08 . 3 

1 I ' 

1 1. 4' 1 3.0  14.5  16. 1 17.6  19.2  20.7  22.3  23. 8 

26.878.4  29. 9 31. 5 33-0  34.6  36.1  37.7  39.2 

42. 273. 845. 346. 945. 4 50. 0 51. 5 53.1  54-6 

I ' I ' ' ' 

57 .6  59. 2 60. 7 62. 3 63 . 8 65 .4  66. 9 68. 5 70.0 

73-1 
88. 5 

03-9 

19.4 


74.7  76.2  77.8  79.3  So. 9 82. 4 84.0,85.5 
90.1  9I.6'93.2  94.7  96.3  97. 8 99.400.9 
05.5^07.008.6  10. 1 II. 7 


13.2  14. 8 16.3 
28. 7 30.3  31. S 

44-1  45-7  47-2 
59.5  61. 1 62.6 


21.022.5  24.1  25.6  27.2 
34. 8|36. 4^37. 939. 541-042. 6 
50.2  51.8  53.3  54.9  56.4  58.0  ; 

65. 7^67. 3 68.8  70.4  71.9  73.5  75.0  76.6  7S.1 
81.  i'82. 7 84.2  85.8  87.3  S8.9  90.4  92.093.5 
96.5  98.1  99.6^01.2  02. 7 04. 3 05.8  07.408.9 
11.9  13.5  15.0  16.6  iS.  I 19.7  21.2  22.8  24.3 
27.4^29.030.5  32.1  33-635-2  36.7  3S-339-S 

42.8  44.445.9  47-5  49-0  50.6  52.1  53-7  55-2 

! I I - 


12G 


TABLE  III. 


Density  of  mercury  at  different  temperatures.  {Centigrade^) 


Temperature. 

Density. 

o 

13.59600 

I 

13-59355 

2 

13.59110 

3 

13-58865 

4 

13.58620 

5 

13-58375 

6 

13.58130 

7 

13-57885 

8 

13-57640 

9 

13-57395 

10 

13-57150 

II 

13-56905 

12 

13.56760 

I2i 

13.56638 

13 

13-56515 

I3l 

13-56393 

14 

13.56270 

Temperature. 

Density. 

14I-  

13.56148 

15 

13.56025 

15^ 

13-55903 

16 

13-55780 

i6i 

13-55658 

17 

13-55536 

17I 

13-55413 

18 

13-55290 

CO 

13-55178 

19 

13-55055 

I9i 

13-54933 

20 

13.54810 

20| 

13.54688 

21 

13-54565 

2li 

13-54443 

22 

13.54320 

224 

13-54197 

Temperature. 

Density. 

23- - -t 

13-54095 

234 

13-53952 

24 

13-53830 

24I 

13-53707 

25 

13-53585 

25i 

13.53463 

26 

13-53340 

264 

13.53217 

27 

13-53095 

274 

13-52973 

28 

13.52850 

284 

13.52728 

29 

13.52606 

294 

13-52483 

30 

13-52361 

127 


TABLE  lY, 


lieduction  of  Fahrenheit  to  Centigrade  scale. 


Fahren- 

heit. 

Ceiiti- 

gi’ade. 

2 

0 

3 

5-10 

34 

I I-IO 

35 

1 6-10 

36 

2 2-10 

37 

0 

M 

1 

38 

3 3-10 

39 

3 9-10 

40 

4 4-10 

41 

5 

42 

5 5-10 

43 

6 i-io 

44 

6 6-10 

45 

7 2-10  : 

46 

7 7-10 

47 

8 3-10 

48 

0 i 

8 9-10 

Fahren- 

heit. 

Centi- 

grade. 

49 

9 4-10 

50 

10 

51 

10  5-10 

52 

II  I-IO 

53 

II  6-10 

54 

12  2-10 

55 

12  7-10 

56 

13  3-10 

57 

13  9-10 

58 

14  4-10 

59 

15 

60 

15  5-10 

61 

16  I-IO 

62 

16  6-10 

63 

17  2-10 

64 

17  7-10 

65 

18  3-10 

Fahren- 

heit. 

Centi- 

grade. 

66 

18  9-10 

67 

19  4-10 

68 

20 

69 

20  5-10 

70 

21  I-IO 

71 

21  6-10 

72 

22  2-10 

73 

22  7-10 

74 

23  3-10 

75 

23  9-10 

76 

24  4-10 

77 

25 

78 

25  5-10 

79 

26  I-IO 

80 

26  6-10 

81 

27  2-10 

82 

27  7-10 

Fahren- 

heit. 

Centi- 

grade. 

83.°.... 

28  3-10 

84 

28  9-10 

85 

29  4-10 

86 

30 

87 

30  5-10 

88 

31  I-IO 

89 

31  6-10 

90 

32  2-10 

91 

32  7-10 

92 

33  3-10 

93 

33  9-10 

94 

34  4-10 

95 

35 

96 

35  5-15 

97 

36  I-IO 

98 

36  6-10 

99 

0 

M 

1 

c<-) 

To  reduce  ceutigrade  to  Falireulieit  ; — Falir.  = Ceu.  x 1.8-}- 32°. 


128 


IND  E X 


Accuracy  of  fire,  to  determine  the Art* 

the  mean  range ‘‘ 

mean  difference  of  range “ 

mean  deflection “ 

mean  reduced  deflection “ 

definition  of  the  accuracy  of  a gun “ 

rectangle  method. “ 

of  small  arms . . .• “ 

absolute  mean  deviation •“ 

mean  deviation “ 

mean  horizontal  and  mean  vertical 

^rror “ 

the  absolute  mean  error “ 

radius  of  a circle  containing  a frac- 
tion of  the  balls “ 

the  per  cent “ 

comparison  of  differentrmethods. . “ 

the  inclination  of  the  target “ 

record  of  target  practice  at  sea “ 

Angle  of  fire “ 

Angle  of  sight “ 

Armament  of  ships  of  war “ 

relation  of  weight  of  battery  to  tonnage.  “ 
how  to  dispose  of  weight  of  battery  to 

best  advantage 

relation  of  battery  to  speed  of  vessel. . . 
kind  of  gun  adapted  to  ships  of  war.  . . . 

Armor,  experiments  against 

plates  and  backing 

laminated 

difficulty  of  bolting 

plates,  resistance  offered  to  penetration 

Armstrong  system,  principles  of 

gun,  description  of 

number  of  parts 

barrel  of 

breech  piece  of 

cascabel  of 

shrinking  on  the  coils 

coils  and  tubes  of 

trunnion  ring  of 

Alloys  used  in  the  fabrication  of  cannon 

guns  constructed  of  homogeneous 

one  of  great  density >. 

experiments  with,  for  cannon  making 


1640 

1641 

1642 

1643 

1644 

1646 

1647 

1648 

1649 

1650 

1651 

1652 

1653 

1654 

1655 

1656 

1657 
1583. 
1583- 

261 

262 


263, 

267, 

271, 


266 
270 
274 
' 866 
867 
867 
867 
869 
646,  647 

648 

649 

650 

651 

652 

653 

654 

655 
141 

143 

144 

145 


2 


INDEX. 


Alloys,  advantages  of  those  of  iron Art.  146 

Backing  for  armor ‘‘  868 

Ballistic  machines,  the  ballistic  pendulum “ 1263 

the  gun  ijendulum “ 1263 

application  of  electricity  to ‘‘  1234 

Bar-iron “ 8.5 

Blakely  gun “ 076 

Blast  Furnace “ 15 

the  stack.  “ 16 

the  boshes..' “ 17 

the  hearth “ 18 

the  tymp 18 

lining  of “ 19 


twyer  arches 

twyers 

twyer  holes 

fire  hearth 

cinder  notch 

tap  hole 

tymp-stopping 

throat  cap  and  cone 

details  of  the  top  of  the 

charging  the 

draft  of,  how  maintained 

pressure  of  blast. 

temperature  of  blast,  how  determined 

fusibility  of  metals,  table  of 

hot  blast 

hot  blast,  effects  of 

heat  of  furnace 

hot  blast,  advantages  of 

w'arm  blast 

heating  the  blast 

starting  the 

working  the 

chemical  .action  in  the 

tapping  the, 

to  preserve  uniformity  of  blast  in  the. 

!Boat  howitzers 


Breech  loading 

advantages  of 

disadvantages  of 

British  naval  guns 

Uroadwell  ring 

Bronze  tor  cannon 

the  copper 

the  tin 

management  of 

uniformity  of  the  alloy 

effect  of  remelting,  on  the  constitution  of  the  alloy 

difficulty  of  making  sound  castings  frour  often  remelted 

alloys 

upon  wliat  the  perfection  of  the  alloy  depends 

qualities  of 

strength  of 

objections  to  rilled  guns  of 

comparative  value  of,  as  a cannon  metal 

Blooming 


( I 


a 


u 


( ( 

(( 

(( 

u 

(( 


20 

21 

23 

23 

24 

25 

26 
28 
27 

30 

31 

33 
S3 

34 
' 35 

SO" 

37 

38 

39 
41 

■ 43 

44 

45 
47 

340,  341 
231 

770 

771 
773 
645 
686 

133 

134 

135 

136 

137 

138 

139 

140 

177 

178 

179 
184,  185 

83 


INDEX. 


3 


Built-up  gTins Art.  G16 

object  of “ lI17 

initial  tension,  principles  of  the  system “ C24 

defects  of  the  system “ 625 

methods  of  application  of  the  system.  “ 626 

varying  elasticity,  principles  of  tlie  system “ 629 

defects  of  the  system “ 6::i0 

longitudinal  strength  of “ G'll 

length  of  hoops “ 682 

number  of  hoops “ 633 

want  of  continuity ‘‘  634 

vibration  in “ 635 

conclusions  with  regard  to ‘‘  636 

Cannon  construction,  upon  what  depends  the  necessity  for  strength  in  “ 186 

Cannon  metals,  qualities  necessary  in “ 147 

properties “ 149 

den.sity “ 150 

hardness “ 151 

brittleness “ 152 

tenacity “ 153 

tensile  strength “ 154 

porosity “ 155 

elasticity-  “ 156,157 

permanent  set “ 158 

elasticity  of  torsion 159 

malleability “ 160 

ductility , “ 161 

difficulty  of  selecting  suitable  material “ 148 

various  qualities  of “ 347 

qualities  uiDon  which  then-  fitness  depend 180 

C.anister  shot “ 800 

rifle “ 801 


Calibre 

Case-shot 

Cast-iron,  composition  of 

varieties 

converting  gray  into  white 

white  into  gray 

gray- 

white.  

diSerent  kinds  of  white 

mottled 

Ca.st-iron,  classification  of 

variation  in  coinposition  of 

difficulties  attending  the  analysis  of 

silicia  in 

manganese  in 

phosphorus  in 

sulphur  in 

want  of  uniformity  of 

diiference  in  strength  of 

chemical  identity  does  not  involve  uniformity  in  mechani- 
cal properties 

cost  of 

comparative  value  of,  as  a cannon  metal 

qualities  of 

comparative  strength  of,  as  a material  for  cannon  con- 
struction  


202 

795 

50 

51 

52 

53 

55 

56 

57 

58 

59 

60 
61 
62 

63 

64 

65 
165 
165 

160 
167 
181,  185 
■ 164 

164 


4 


INDEX. 


Cast-iron,  tensile  strength  of 

the  strongest,  does  not  make  the  most  enduring. . . 

variation  of  density  and  tenacity 

how  improved 

effect  of  different  treatment 

Castings,  improvement  in 

construction  of  ...  

rate  of  cooling 

time  required  for  cooling 

effects  of  irregular  cooling 

high  iron 

practical  treatment  of  iron  in  fusion 

pi'oof-bars 

molecular  constitution  of  cannon  metals 

crystallization 

development  of  crystals 

chilled 

effect  of  crystallization  on  strength 

size  of  crystals 

effect  of  sudden  change  of  form  in 

effect  of  age  on  endurance  

standard  of  quality  in 

comparison  with  standard 

means  of  comparing. . . 

Charcoal 

woods  used  for 

conversion  of  wood  irrto 

effect  of  temperatrrre  employed  in  conversion 

qualities  of .- 

how  prepared  as  an  ingredient  of  gunpowder 

danger  of  spontaneous  combustion  in  fresh  ground. . 

Cold-short  iron 

Chamber 

Concussion,  as  an  effect  of  the  inrpact  of  a projectile 

Crusher  gauge 

Dangerous  space 

Densimeter 

adjrrstments  of 

use  of 

Determining  density  of  gun  iron 

position  of  trarnnions 

Detonation,  explosion  by 

explosives  capable  of 

how  produced 

nature  of 

illirstration  of  explosion  by 

Deviation  of  projectiles 

effect  of  wind  on 

effect  of  variable  projectile  force  on 

effect  of  rotation  of  the  earth  on 

effect  of  faulty  disposition  of  the  line  of  sight  on, 

influence  of  the  state  of  the  air  on 

of  spherical  projectiles 

effect  of  windag-e  on 

effect  of  eccentricity  on 

of  elongated  projectiles  

of  conoidal -headed  projectiles 

of  flat-headed  projectiles 


Art. 

i ( 
U 
( ( 
u 
(( 

( ( 
(( 
(( 
(; 
C( 

u 

(( 

( i 

u 

It 

u 


ii 
I ( 
<; 


( i 

u 
( ( 
i i 

u 


u 

i t 

u 


(6 

u 

(( 

u 

u 


lfl4 

1G4 

3d0 

SUi 

348 

3T3 

36.) 

3G4 

3G7 

368-370 

3.71 

3.53 

35.5-3.50 

358 
3.59 

359 
360-361 

363 

363 

366 

373 

374 

376 

377 
1083 
1083 
1085 

1089 

1090 

1099 

1100 
64 

213-313 

853 

1340  ' 

1639 
388 
390,  391 
392,  394 
38.3 
334.  33.5 

1042 

1043 

1044 

1045 

1046 
823 

823 

824 

825 

826 

827 

828 

829 

830 
833 
839 
841 


INDEX. 


5 


Drift Art.  842 

Dimensions  of  naval  ordnance “ 22(j 

Descriptive  list  of  guns “ (i09 

Devices  on  cannon “ 22.) 

Dynamite “ 1397 

Distances,  determining “ 1G2S 

correcting  by  previous  rounds “ 1G29 

judging  of “ 1029 

determining  by  angle  subtended  by  the  mast  of  the 

enemy “ 1G30 

horizontal  angle  taken  at  bow  and  stern . ‘‘  10.31 

using  ship’s  own  mast  as  the  given  height  “ 1632 

observing  the  angular  distance  from 

horizon “ 1033 

the  velocity  of  sound “ 1634 

three  point  problem “ 1635 

Boulenge’s  Telemeter “ 1636 

plane  tables ‘ 1637 

Eastman’s  breech  closing  system “ 690 

Elevating  screws “ 16(!0 

Elongated  projectiles,  origin  of “ .714,715 

advantages  of “ 726 

disadvantages  of ; “ 727 

English  experimental  guns ‘‘  675 

Endurance  of  guns  in  service • 605 

Electro-ballistic  machines “ 1231 

the  Navez-Leurs  chronoscope “ 1 273 

the  pendulum.  “ 1238 

the  disjunctor  “ 1242 

the  electric 

currents.. . . “ 1243 

arrangement 

of  targets. . . “ 1 244 

operation  of 
the  instru- 
ment  “ 1245 

Benton’s  thread  velocimeter “ 1247 

the  pendulum 

machine 1248 

the  compres- 
sors  “ 1250 

the  cannon 

targets “ 1252 

the  small-arm 

targets “ 1253 

to  determine 
the  time...  “ 1259 

Le  Boulenge’s  chronograph “ 1255 

the  electro- 
magnets. “ 1259 

the  dis- 
junctor. . “ 1262 

theory  of 
the  in- 
strument. “ 1267 

method  of 
adjust- 

ment. ...  “ 1271 


6 


INDEX. 


Electro- ballistic  maclimes,  Le  Boulenge’s  cliroiiograpli,  method  of 

taking  ve- 
locities. . . Art.  1279 


method  of 
correct- 
ing meg- 

ularities..  “ 1280 

Schultz’s  chronoscope “ 1287 

the  cylinder “ 1283 

the  vibrating  fork. . “ . 1289 

the  interrupter “ 1290 

the  Euhmkorff  coU.  “ 1291 

the  pendulum. “ 1292 

the  micrometer. .. . “ 1293 

the  batteries “ 1294 

the  targets “ 1295 

principles  of  the 

machine “ 1296 

to  use  the  chrono- 

ecope “ 1297 

Bashforth’s  chronograph “ 1298 

description “ 1299 

the  targets “ 1300 

arrangement  of 

screens . “ 1301 

Noble’s  chronoscope,  description. .■  “ 1302 

rate  of  the  discs. .. . ‘‘  1303 

to  obtain  the  elec- 
trical record.s “ 1305 

connection  with  the 

bore  of  gun “ 1306 

Le  Boulenge’s  electric  clepsydra “ 13o7 

d escrip- 

tion....  “ 1308 

basis  of 
calcula- 
tion of 

times..  1312 


e X p e r i - ' 
m e ntal 
deter- 
mina- 
tion of 

times..  “ 1316 

use  of  the 
i n stru- 

ment..  “ 1321 


Force  of  gravity  as  an  element  in  bal- 
listics  

Explosive  agents 

Explosives,  definition  of 

Ex^rlosive  effect 

compounds 

mixtures 

different  classes  of  

nitrate  mixtures 

chlorate 

E.xplosion,  ini.ensity  of 


1323 
1031 
1031 
1')  2 
10:3 

10:  4 
1025 

10.5 
io;lo 
10,.  9 


IXDEX. 


r 


Explosion,  means  of  causing .Art.  1040 

method  of  producing •'  1041 

Explosive  compounds,  general  consideration  of “ 1375 

guncotton “ 137(5 


manufacture  of 1377 

purification  of  the  cotton “ 137S 

treatment  with  acid  “ 1379 

to  remove  the  acid 1380 

Abel’s  method *•  1380 

pulping 1382 

compressing: *•  1383 

general  properties “ 1384 

forms  in  which  used “ 1335 

uses “ 138(5 

mode  of  firing “ 1387 

nitro -glycerine “ 1388 

method  of  manufacture “ 1390 

general  projierties “ 1391 

mode  of  firing “ 1392 

transportation  of... '•  1393 

stability  and  permanence. .. .'  “ 1394 

uses “ 1395 

compounds  of  nitro -glycerine “ 139(5 

dynamite “ 1397 

lithofracteur “ 1398 

duaUne “ 1399 

Exterior  form  of  guns 215,311 

Extreme  proof  of  trial  guns “ GOl 

Fabrication  of  Cast-icon  CJuns “ 445 

contract  with  gun  formder  “ 378 

preparing  stock  for  a blast  of 

gun-iron “ 339 

piling  pigs,  to  obtain  identity  in 

quality  of  metal “ 34.2,  343 

furnaces  for  melting  gun^iron  . , . “ 443,  447 

charging  the  furnaces  -149 

first  and  second  fusion  iron  “ 450 

charge  used “ 451 

distribution  of  metat ‘‘  223 

molding “ 453 

molding  composition ” 454,  45(i 

models “ 457 

flasks “ 458,  459 

process  of  molding “ 4G0,  4(55 

core  baiTel  in  hollow  casting ‘‘  4(50 

preparing  the  core “ 437,  439 

casting  pit “ 470 

placing  the  flask “ 471 

cranes “ 472 

adju.sting  the  core “ 473 

melting  down  the  charge “ 475,  477 

tapping  the  furnace  “ 479 

heating  the  pit 481 

cooling  heavy  castings  “ 482 

withdrawing  core-barrel ‘‘  484 

removing  heavy  castings  from  pit  “ 487 

condition  of  rough  casting ‘‘  488 

heading  lathe  for  heavy  guns  ...,  “ 489 


8 


INDEX. 


Fabrication  bf  Cast-iron  Guns,  boring  lathe,  adjustment  in Art. 

mea.suring  gun-castings. “ 

turning  down  gun-castings “ 

removing  the  sinking-head “ 

cutting  out  specimen “ 

boring  lathe “ 


adjustment  in 

boring 

trunnion  lathe 

planing  machine 

cutting  hole  for  elevating  screw. . . 

drilling  the  vent 

Bronze  Howitzers 

pattern  

flask 

molding 

runner  

drying  oven  

drj'ing  the  mold  

pit  for  mold  

placing  flask 

charging  the  furnace  

treatment  of  the  melted  metal 

melting  down  the  charge 

made-up  charges 

casting 

runner-box  for  casting 

tapping  the  furnace 

Firing  means  of 

by  electricity 

different  kinds  of 


u 

U 


direct 


ricochet 

curved 

plunging 

solid-shot 

shell 

shrapnel 

grape  and  canister 

horizontal 

vertical 

small  arm 

Fraser  system  of  gun  construction 

Form  of  gun,  experiments  to  determine  the 

French  naval  guns 

castings  of 

the  tubes  of 

building  up  the 

the  hoops  of 

breech  screw  of 

safety-catch  for 

to  open  the  breech  of , . . , 

loading  the  , . 

Field  fortifications 

definitions 

plans 

profiles 

artillery  in  field  works 


U 

(( 

u 


490,  494 
495 
49(i 

498 

499 

500 
502 

503,  505 
500,  508 
509 
511,  513 
514 
516 
517,  519 

520 

521 

522 

523 

524 

525 

526 

527 

528 
529,  531 

532 

533 

534 
536 

1438 

1458 

1693 

1694 

1695 

1701 

1702 

1703 

1704 
1708 
1711 

1714 

1715 
1723 

656,  658 
221 
078 
680 
681 
682 
083 
689 
694,  697 
095 
696 
1806 
1807 
1821 
1830 
1842 


INDEX. 


9 


Field  defence  of  walls . . . . 

building 
village. . 
bridge. . 
attack  of  works. ... 

surprise 

open  attacks 

defence 

sorties 

Fulminates 

of  mercury . . . 

silver 

Fuzes 


Tke  time  fuze 

requirements  of 

Tke  navy  time  fuze 

safety-plug  for  

composition  for 

paper  case  for 

driving  the  compo.sition,  machine  for’. . 

driving  the  composition  

wat;3r-cap  for 

safety-cap- for 

fuze-stock  tor 

time  of  burning 

varieties 

general  working  fuze 

to  shorten  the 

testing 

Time  fuzes  for  rifle  projectiles 

Time- fuzes,  imperfection  of 

Time  fuzes,  premature  explosion  of 

Their  action  and  result  to  be  reported 

The  Bormann  fuze 

operation  of 

advantages  of 

Percussion  and  concussion 

Concussioir  

The  Splingard  fuze 

The  Bacon  and  McIntyre  fuze 

Percussion 


advantages  of 
Scheukle  fuze. 
Parrott  fuze . . 
German  fuze  . 


Art.  1845 

1847 
“ 1851 

“ 1854 

“ 1858 

“ 1850 

“ 1801 

“ 1808 

“ 1805 

“ 1400 

“ 1401 

“ 1403 

“ 1400 

1461 
“ 1463 

“ 1463 

“ 1404,1407 
“ 1405 

“ 1400 

“ 1470 

“ 1473 

“ 1474 

“ 1475 

“ 1479 

“ 1477 

“ 1477 

“ 1477 

“ 1478 

“ 1479 

“ 1477,1480 
“ 1481 

“ 1483 

“ 1484 

“ 1485 

“ 1487 

“ 1489 

“ 1490 

“ 1491 

“ 1493 

“ 14;)4 

“ 1195 

“ 1490 

“ 1497 

“ 1500 

“ 1501 


Mortar. “ 1503 

Itunniug,  for  mines  and  blasting ■“  1505 

Detonating “ 1507 

Fulminate  exploder “ 1508 

Electric  exploders “ 1509 

Electric, “ 1509 

Platinum- wire “ 151-4 

advantages  of “ 1515 

The  dynamo-electric  igniter. “ 1510 

The  dynamo-electric ' “ 1517 

Removing,  from  loaded  shell “ 830 

For  15 -in  shell “ 1570 

Gas- check  for  breech  loaders “ 685 


10 


INDEX. 


Gatling 


German 


gun,  description  of 

revolving  gear  of  

hopper  of 

carrier  of 

lock  cylinder  of 

locks  of  

breech  casing  of 

traversing  gear  of 

elevating  gear  of 

removing  the  locks  of 

feed  drum  of 

working  the 

comparison  with  howitzers 

Ijreservation  of 

directions  for  taking  apart 

putting  together. . . 

naval  guns 

features  of  the  manafaclure 

old  Krupp  construction 

new  

the  central  tube 

the  breech  plug 

the  gas  check 

the  vent  tube 


Art.  233 

“ 234,  241 

233 

“ 237 

“ 238 

Arts.  239,  244,  246,  231 

'•  240 

“ 242 

“ 243 

“ 245 

247. 232 

Arts.  249,  230.  253,  254,  235 

“ 236 

“ 237 

“ 239 

“ 260 

“ 701 

“ 703 

703 

“ 704 

“ 703 

“ 707 

“ 708 

“ 709 


Gomer  chamber “ 214 

Grape  shot ; “ 799 

Guncotton “ 1376 

Gun,  general  form  of “ 189 

construction,  theory  of “ 276  ' 

making,  improvements  in “ . 224 

interior  form  of  a “ 201 

Guns,  how  distinguished “ 188 

cast  iron,  detection  of  coming  fracture  of “ 170 

Gunpowder “ 1047 

ingredients  of “ ' 1048 

purity  of  ingredients  necessary  to  security  of  manufac- 
ture  ^ “ 1049 

proportions  of  ingredients “ 1093 

imeparing  and  mixing  the  ingredients “ 1095 

mixing  machine '■  1101 

incorporation  of  the  ingredients,  importance  of  the 

process ‘‘  1103 

time  required  for. . “1104,1114 
the  effect  of  imper- 

I feet “ 1105 

miU  used  for “ 1106 

the  operation “ 1111 

capacity  of  a factory  for  making " 1115 

mill-cake “ 1116 

danger  of  incorporatiom “ 1118 

drenching  apparatus,  to  prevent  explosion  in  factory. . . “ 1121 

pressing  the  mill-cake “ 1125 

description  of  press “ 1127 

dilficulty  of  obtaining  uniformity  of  results  in  pressing.  “ 1133 

Gunpowder,  method  of  obtaining  powder  of  uniform  density 1133 

graining “ 1136 

granulating- machine “ 1137 

method  of  granulating  powder “ 1140 


INDEX. 


11 


Gunpowder,  danger  attending  granulation 

dusting  and  glazing 

the  dusting  reel 

the  glazing  barrel 

drying 

special  powders 

terms  applied  to  different  kinds  of  powder 

mammoth 

prismatic 

hexagonal 

watiie 

pebble i 

pellet 

rifle-large -grain 

machine  for  making  special  powder 

explosion  of 

ignition  of 

inflammation  of 

combustion  of 

xelocity  of  combustion 

explosive  force  of 

products  of  combustion . , 

inspection  of 

general  qualities  of 

examination  of.  by  hand 

by  flashing 

size  of  grain 

gravimetric  density  of 

specific  gravity  of 

the  mercury  densimeter 

process  of  taking  the  density 

initial  velocity  of 

analysis  of 

strain  upon  the  gun 

pressure  gauges 

r , curves  

hygro  metric  qualities  of 

inspection  report 

marks  on  the  barrels 

preservation  and  storage 

storage  on  shore 

preservation  of,  in  shore  magazines 

classification  of  “ 

issue  of,  from  shore  magazines 

magazine  ledger 

transportation  of 

reception  of,  on  board  ship 

storing,  on  board  ship 

tanks 

system  of  marking 

restoring  unserviceable 

condemned 

purchasing  abroad 

Gun  carriages  of  United  States  Navy 

general  considerations 

steam  power  for  working 

* requirements  of  mechanical 

disappearing  systems 


Art. 

<; 

u 


C ( 


u 


u 


u 

(4 

U 

u 

u 

u 

( 4 
ic 


ti 


1143 

1144 
1149 
1153 

1158 

1159 
1163 

1163 

1164 

1165 

1166 

1167 

1168 

1169 

1170 

1173 

1174 
1177 
1187 
1193 
1198 
1304 
1209 
1310 
1211 
1213 

1213 

1214 

1215 
1316 
1224 
1230 

1346 
1329 
1331 

1344 

1345 

1347 

1348 

1353 

1354 
1356 

1355 
1360 
1359 

1373 

1374 
1367 
1.368 
1369 

1349 

1350 

1351 
883 
883 
885 

887 

888 


12 


INDEX. 


Gun  carriages, Marsilly  broadside,  nomenclature Art. 

dimensions “ 

the  brackets “ 

the  breech  piece “ 

the  socket  plate “ 

the  roller  handspike “ 

the  truck  axle “ 

the  trucks “ 

the  saucer “ 

resistance  to  recoil “ 

manoeuvering  the  carriage “ 

elevation  obtainable “ 

preservation  of “ 

tackles  for “ 

metallic  gun-tackle,  blocks  for. . “ 

breechings  for “ 

wrought  iron  carriages  for  8-iu.  gun,  nomenclature 

dimensions.. 
the  brackets.  “ 

the  transoms  “ 

the  truck  axle  “ 

elevating  gear  “ 

side  and  train- 
ing bolts . . “ 
the  breast 
piece.  ... 
cap  square..  “ 

. the  recoil ...  “ 

advantages  of  urought-iron. ...  “ 

mounting  Parrott  rifles  in  broadside “ 

pivot  carriages “ 

Wooden  11-iu.  Pivot. 


the  carriage 

the  brackets 

the  transoms 

the  journal  plates 

the  compressor 

' the  slide 

the  compressor  battens 

the  hurters 

the  metal  tracks 

the  bossed  sockets 

the  eccentrics 

the  recoil 

the  breeching 

shipping  the  levers 

transporting 

pireventer  breeching 

Iron  11 -in.  Pivot. 

nomenclature 

dimensions 

the  slide 

the  transoms 

the  hurters 

coincidence  of  pivot  holes,  how 

secured 

form  of  rail 

transporting 


(( 

a 

u 

u 


u 


890 

890 

891 

892 
89.3 
894 
89.5 
890 

897 

898 

899 

900 

901 
903 
903 

903 

904 

904 

905 
900 

907 

908 

909 

910 

911 
913 

913 

914 

915 
910 

917 

918 

919 
92P 
921 

923 
933 

924 

925 

920 

927 

928 

929 

930 

931 
933 


933 

933 

934 

935 

936 


937 

938 

939 


rNDKX. 


13 


Gun  carriages,  Iron  11-in.  Pivot,  the  caniage Art 

the  brackets “ 

the  bed -plates “ 

the  journal-plates “ 

form  of  eccentric  axle “ 

the  compressor. “ 

recoil “ 

necessity  of  eccentric  rollers  in 

slide “ 

20-Pdr.  Rifle  Pivot “ 

15-in.  Turret. 


nomenclature 

the  slide 

the  carriage / . . . 

the  m-and-out  gear 

the  carriage  rollers 

the  compressor  gear 

the  compressor  plates . . . . 
action  of  compressor  gear. 

elevator  rest 

the  hurters 

elevation 

the  port  stopper 

loading  appliances 

the  rammer  and  sponge . ; 

pointing  the  turret 

turret  sights 

the  turret 

pilot  house 

Mortar, 

nomenclature 

dimensions 

the  carriage 

the  brackets 

the  transoms 

running  in  and  out 

the  mortar  circle 

eccentric  rollers 

the  deck  supports 

Howitzer,  boat  (wood), 

nomenclature. . . 
the  slide ........ 

the  compressor. . 

elevation 

the  boat  carriage 

pivots 

ihvoting 

Howitzer,  boat  (iron), 

nomenclature 

dimensions 

the  slide 

the  bed-plate. ... 

the  bed 

recoil 

the  sides 


C4 


U 

u 

(( 

u 

u 

u 

(( 


(( 

u 


( ( 


Howitzer,  field, 


nomenclature 
the  carriage.  . 


u 


940 

941 
943 

943 

944 

945 

946 

947 

948 

949 

950 

951 
953 

953 

954 

955 

956 

957 

958 

959 

960 

961 
963 

963 

964 

965 

966 

967 

967 

968 

969 

970 

971 
973 

973 

974 

975 

976 

977 

978 

979 

980 

981 

983 

983 

984 

985 

986 

987 

988 


989 

990 


14 


IIO)EX. 


Gun  carriages,  Howitzer,  field,  the  trail Art.  091 

the  carriage  ashore ‘‘  992 

the  carriage  in  the  boat “ 992 

skids  for  landing “ 994 

implements ■ “ 995 

Enghsh  Naval 996 

Scott’s  Broadside  (English), 

nomenclature “ 996 

the  carriage “ 997 

the  slide ‘‘  998 

deck  tracks “ 999 

the  pivot “ 1000 

the  dimensions “ 1001 

self-acting  compressor.  “ 1002 

elevating  gear “ 1003 

eccentric  gear “ 1004 

in  and  out  gear “ 1005 

training  gear “ 1006 

advantages  of  mechan- 
ical carriages “ 1007 

bow  compressor “ 1008 

training  gear “ 1009 

high  and  low  carriages.  “ 1010 

depression  carriages. ..  “ 1011 

English  Turret  the  slide “ 1012 

compound  vertical  pivoting  gear . ‘‘  1012 

elevation “ 1013 

the  carriage '.  “ 1014 

recoil “ 1015 

the  turret “ 1016 

in-and-out  gear “ 1017 

elastic  buffers “ 1017 

pointing “ 1018 

turret  indicator “ 1019 

night  firing  “ 1021 


Hydraulic  Appliances  (English)  general  description  “ 1024, 1(>25 

running  in  and  out.  “ 1026 

loading “ 1028 

sponging “ 1029 

advantages “ 1030 

Gun  Implements  “ 1724 


staves “ 1724 

sponges “ 1725 

rammers 1729 

ladles  “ 1731 

worms “ 1732 

sectional  staves 1733 

Hand  grenades “ 801 

Howitzers “ 229 

Hydrometer “ 384 

use- of “ 386,  387 

Hot  blast  iron “ 40 

Hart’s  elevating  screw “ 1665 

Impact,  force  of “ 880 

Incendiary  preparations “ 1563 

carcass “ 1564 

incendiary  match “ 1565 


INDEX. 


15 


Incendiary  preparations,  hot-shot 

Injuries  to  guns  from  the  projectile 

powder 

Inspection  of  projectiles 

grape  and  canister 

guns  at  termination  of  cruise .... 

vents 

new  guns  

Inspecting  instruments  for  guns 

mirror 

searcher 

cylinder  gauge . 
measuring  staff, 
chamber  guage 
star  gauge 


head  of 

measuring  points 
sliding  rod  for.  . 

handle  for 

adjustment  of. . . 
muzzle  rest  for.  . 

disk . 

use  of 


Art. 


U 


u 
(& 
( ; 
(( 


vent  guide 

verifying  interior  positions  of  vents 

vent  gauges 

vent  searcher 

profile  boards 

' beam  calliper 

cascabel  block 

trunnion  guage 

trunnion  square 

, trunnion  rule 

templates 

impression  taker  for  vents 

gutta-percha  impressions 

Laboratory  materials,  classification  of 

nitre 

chlorate  of  potassa 

charcoal 

sulphur 

antimony 

sulphuret  of  antimony 

gunpowder 

lampblack .' 

coloring  materials 

substances  which  give  color  to  flames 

substances  which  produce  sparks 

turpentine 

rosin 

tar 

pitch 

alcohol 

gum-arabic 

beeswax 


( I 

u 

u 


for  preparing  cartridges 

Laboratory  buddings 

furnaoe 


1506 

cns 

008 

812 

815 

611 

613 

538 

540 

541 

543 

544 
540 
548 

550 

551 

553 

554 

555 
550 

557 

558 
502 
560 
508 
571 
573  / 
575 

577 

578 

579 

580 
583 
580 
591 
593 

1407 

1408 

1409 

1410 

1411 
1413 

1413 

1414 

1415 
1410 

1417 

1418 

1419 

1421 

1422 
1433 
1425 

1420 
1-427 
1428 

1404 

1405 


16 


INDEX. 


Laboratory  operations Art. 

compositions “• 

- Landing  a naval  force 

tbe  base “ 

preparations “ 

details “ 

the  boats ‘• 

the  landing ‘‘ 

on  the  march “ 

advance  guards “ 

rearguards  “ 

bivouac “ 

grand  guard “ 

engaging 

the  attack “ 

the  skirmishers “ 

the  infantry “ 

the  artillery ....  “ 

the  defence “ 

field  fortification “ 

the  retreat “ 

destruction  of  bridges “ 

p.a.ssage  of  a defile “ 

the  embarkation “ 


Length  of  bore 

Limit  of  thickness  of  cannon 

Line  of  sight  

Line  of  fire 

Line  of  metal 

Lithofracteur 

Loading ' 

rapidity  of 

Loading  .small  arms 

mortars 

Loaded,  keeping  guns 

Magazines  on  shore 

service  of 

on  board  ship. 

construction  of 

flooding 

lighting 

seiTice  of 

screens  for 

dampness  of 

ventilation  of i 

Marking  samples  of  gun  iron 

Marking  guns 

Marvin’s  estimator 

hletallurgy  of  iron 

Mortars,  definition  of 

construction  of 

Motion  of  projectiles,  the  equation  of  the  path  of  a projectile  in 

non-resisting  medium 

co-ordmates  of  the  vertex 


maximum  range 

time  of  flight  on  a horizontal  plane 

elevation  necessar}'  to  cause  a projectile  to 
pass  through  a given  point 


140G 

1429 

1701 

1703 

1704 
1708 
1770 
1773 

1777 

1778 

1782 

1783 
1787) 

1788 

1789 
179.1 

1790 
1797 
1800 
1800 
1800 
1871 
1873 

' 1873 
203 
021 
1183 
1183 
1187 
1398 
1107 
1178 
1181 
1180 
1173 
1313 
1317 

1301 

1302 
1301 
1306 

1370 

1371 
1371 
1371 

380 

11.1 

1338 

1 

227 

228 

1734 

1731 

1731 

1736 

1737 


INDEX. 


17 


Motion  of  projectiles,  envelop  of  the  trajectories Art.  1787 


velocity  of  a projectile  at  any  point  of  its  path.  “ 1738 

direction  of  the  path  at  any  point “ 1789 

co-ordinates  of  the  point  where  a projectile 
will  strike  an  inclined  plane  passing  through 
the  point  of  projection,  the  range  and  time 

of  flight  on  the  inclined  plane “ 1740 

Remarks  on  the  utility  of  the  formulas  ob- 
tained when  the  resistance  of  the  air  is  not 

con-sidered  “1741,  1742  . 

Examples “ 1742 

Motion  of  a projectile  in  air “ 1743 

integrals  for  the  determination  of  x,  y, 

and  f,  deduced, “ 1744 

computation  and  use  of  the  tables  for 

finding  x.  Y,  and  T “ 1745 

determination  of  x,  y,  and  and  the 
range  on  a horizontal  plane  by  means 

of  the  tables “ 174(5  ' 

determination  of  ?/ “ 1748- 

examples Arts.  17-49,  1750,  1751 

motion  of  a projectile  when  the  effect 

of  gravity  is  not  considered 1753,  1754 

computation  of  tables  I'lII,  IX,  X and 
XI “ 175G' 


examples  of  the  use  of  tables  YIII,  IX, 


X and  XI “ 1757 

Naval  operations  on  shore “ 1700- 

Naval  howitzers “ 230 

Nitro-glycerine  “ 1388 

Nomenclature  of  guns “ 190 

breech “ 191 

cylinder “ 192 

curve “ 193 

chase “ 194 

muzzle “ 195 

traunions “ 196 

rim  bases “ 200 

Ordnance,  definitions  of  the  term “ 187 

Palliser  system  of  conversion “ 671 

theory  of “ 672 

method  of  construction “ 673 

Parson’s  system  of  conversion  “ 674 

Parrot  gun “ 639 

barrel  of “ 640 

the  hoops “ 641 

placing  the  reinforce ‘ ‘ 642 

Percussion  locks  for  naval  ordnance “ 232 

Point  blank “ 1584 

Powder  proof “ 598 

Picric  powder “ 1403 

Plane  of  fire “ 1583 

sight “ 1583 

P'josphorus  bronze “ 142 

Pouching  and  racking “ 876,  879 

Pyrotechny ' “ 1404 

Pig-1. eds “ 48 

Piling  pigs “ 49 


IS 


INDEX. 


Pig'S,  difference  in  quality  of Art.  344 

Penetration  of  projectiles “ 84<i 

effect  of  elasticity  in  the  resistance  to ... . “ 847 

penetration  of  spherical  projectiles ‘‘  848 

elongated  projectiles “ 841) 

formula  for  the  perforation  of  iron  plates.  “ 850 

influence  of  the  form  of  head  of  a pro- 
jectile on.. . . “ 851 

effect  of  oblique  impact  on,  with  reference 

to  form  of  head “ 852 

effect  of  increasing  the  velocity  of  pro- 
jectiles  “ 803 

best  material  to  resist “ 807 

effects  on  wood ‘‘  673 

ear-th “ 874 

masonry “ 875 

the  law  of ‘‘  1758 

fonnula  for  the  amount  of  penetration 

deduced “ 1759 


Pivot  carriages “ 892 

Portfire “ 1450 

substitute  for “ 1457 

Pointing Arts.  1582,1084 

instruction  in Art.  1027 

guns  and  howitzers 1000 

under  ordinary  angles “ 1007 

upon  what  accuracy  of  aim  depends.  . “ 1007 

when  the  axis  of  trunnions  is  inclined  “ 1008 

small  arms “ 1074 

mortars Arts.  1075-1079 


bearing  of  the  enemy . .Art. 

the  ‘‘director” “ 

concentrated  fire “ 

the  directing  battens “ 

the  converging  line  “ 

to  calculate  the  angles  for  concentration “ 

to  mark  the  beams  for  concentrated  fire ‘‘ 

the  elevation.. “ 

to  mark  the  heel  of  the  ship  “ 

Preparing  ammunition ‘‘ 

making  cartridge  bags “ 

cartridge  bags  for  saluting “ 

inspecting  cartridge  bags “ 

preservation  of  cartridge  bags “ 

filling  cartridge  bags “ 

marking  cartridge  bags '■ 

service  charges “ 

cartridges  for  mortars “ 

cartridges  for  hot  shot " 

strapping  shell “ 

filling  shell “ 

charges  of  powder  for  shell “ 

bursting  charges  for  shell “ 

loading  and  fuzing  shell “ 

Y packing  shell *' 

. ^ wads “ 

grommet  wad ‘‘ 

junk  wad ‘‘ 


li)S2 

1088 

1685 

1686 

1687 

1688 

1690 

1691 

1692 

1535 

1536 
1.5;J7 

1538 

1539 

1540 

1541 

1542 

1543 

1544 

1545 

1547 

1548 

1549 

1550 
1552 
1.558 

1554 

1555 


IXDKX. 


19 


Preparing  animimition.  boat  aramnnition Art.  looO 

fixed  ammunition looG 

stand  o£  ammunition “ 1557 

packing  boat  aminiinition “ 155S 

fitting  cartridges  for  boat  amniunition  “ 155. > 

metallic  cartridges “ 1550 

dummy  cartridges  for  small  arms ‘‘  15(51 

blank  cartridges  for  smail  arms “ 15G2 

Preparation  of  iron  ores “ 2 

dressing  “ 3 

weathering “ 4 

breaking “ 5 

roasting “ (5 

Preponderance “ 199,318 


example  to  compute  the,  of  a 15-in.  gun .4rts.  322,333 

effect  on  the,  of  a change  in  the  position  of  the 

trunnions Art,  336 

Pressure  gauges “ 1332 

Primers,  percussion “ 1439 

fabrication  of ‘‘  1440 

' pacldng “ 1443 

testing “ 144(5 

returned  from  ships “ 144(5 

friction “ 1447 

composition  for 1448 

when  and  how  used 1449 

allowance  of “ 1451 

stowage  of “ 1450 

spur  tubes  for “ 1452 

how  used “ 1453 


electric “ 1459 

Projectiles,  fabrication  of ‘‘  802 

pattern  for “ SO  ! 

molding  of “ 804,  805 

bouching  of  “ 806 

chilled 807,  805 

Palliser: “ SOS,  809 

steel 810,  805,  870 

Whitworth’s  steel " 811 

inspection  of “ 812 

sohd “ 813 

hollow “ 814 

.smooth  bore,  table  of  gauges  for “ 815 

preservation  of “ 850 

piling  “ 817 

lacquering “ 818 

to  find  the  number  of  balls  in  a pile “ . 821 

deviations  of “ 822 

elongated,  deviations  of 832 

line  of  flight  of  elongated “ 837 

elongated,  positions  of  axes  during  flight ••  838,  840 

effects  of “ 843 

impact  of  " 844 

different  effects  produce  bj’  the  impact  of “ 845 

concussion  produced  by  impact  of “ 853 

armor  piercing “ 854 

spherical,  for  use  against  armor “ 855 


20 


IXDI5X. 


Projectiles,  armor  piercing,  effect  of  shape  on  their  power Art. 

effect  of  flat-ended  form  for  armor-piercing. ..  *• 

advantage  of  rifle  projectiles  for  punching  armor 

elongated,  for  use  against  armor “ 

effects  of  conical-ended  form  for  armor-piercing “ 

the  ogival,  the  best  form  of  head  for  armor-piercing. .. 

effect  of  hardening “ 

advantage  of  steel  over  chiUed “ 

classification  of “ 

spherical “ 

elongated “ 


length  of 

form  of  heads 

ogival  heads  

form  of  body  which  would  experience  the  least  resi-t- 

ance  in  passing  through  a fluid 

form  of  body  which  would  experience  the  least  resist- 
ance from  the  air 

elongated,  studded 

system  of  .studding 

elongated,  expanding 

Parrott’s '. 

Dahlgren’s  rifle ' 

Shenkle’s 

Hotchkiss’ 

lead- coated 

solid 

hollow 

punching  effects  of,  how  compared 

withdrawing  a 

Puddling  furnace 

process 

furnace,  charging  the 

tools 

substitutes  for  manual 

manipulation  of  the  molten  iron  in 

white  iron 

gray  iron 

balls 


Quoins 

Quick  match 

Range 

at  level 

Rammer,  marks  on 

Reffye  gun 

cartridge 

Red  short  iron 

Running  out  cannon 

Rifle,  difficulty  of  loading  the 

Rifle  cannon,  introduction  of 

difficulties  of  perfecting 

progress  of  construction  of 

designing 

early  experiments  with 

calibre  of 

form  of  groove  in • 

having  projectiles  of  hard  metal,  fitting  the  peculiar- 
form  of  the  bore  mechanically 


8.o6 

8()6 

8.57 

856 

860 

861 

862 

865 

774 

775 

776 
7TT 
778 
770 

780 

781 
7S2 
788 
785 

785 

786 

787 

788 

789 

791 

792 
881 

1571 

74 

75 

76 


78 

79 

80 
81 
82 

1660 

1455 

1585 

1586 
1568 

698 

699 
65 

1574 

716 

717 

721 

722 
724 
724 
780 
731 

754 


INDEX. 


21 


Rifle  cannon,  with  projectiles  having  soft  metal  studs,  or  ribs,  to  fit 

the  grooves  Art. 

with  projectiles  having  a soft  metal  enveloi^e  or  cup, 

which  is  expanded  by  the  gas  in  the  bore 

with  projectiles  having  a soft  metal  coating,  larger 
in  diameter  than  the  bore,  but  which  is  compressed 

bj'  the  gas  into  the  form  of  the  bore '■ 

Rifling,  definition  of “ 

origin  of ......  Arts.  71 1,  ' 

difficulty  of  application  to  great  guns Arts. 

object  of “ 

method  of ‘‘ 

lands “ 

twist “ 

uniform  twist “ 

uniformly  increasing  tvvist “• 

increasing  twist,  advantages  of  the “ 

objections  to  the “ 

uniform  twist,  advantages  of  the “ 

character  of  grooves  in “ 

the  loading  and  driving  edge “ 

advantages  of  radial  bearing  in “ 

rounded  angles  in “ 

cutting  the  grooves  “ 

a system  of ‘‘ 

different  systems  of,  classified ‘‘ 

definition  of  centring “ 

'Whitworth’s  system  of “ 

Yavasseur’s  system  of “ 

Scott’s  system  of “ 

Lancaster’s  system  of “ 

comparative  advantages  of  systems  of  the  first  class ‘ ‘ 

the  Woolwich  system  of “ 

the  Shunt  system  of “ 

comparative  advantages  of  the  systems  of  the  second  class.  “ 

the  Parrott  sy.stem  of ■’ 

comparative  advantages  of  the  systems  of  the  third  class  . . “ 

ICrupp’s  method  of “ 

the  German  system  of “ 

cpraparativc  advantages  of  the  systems  of  the  fourth  class.  ‘‘ 

Rifle  projectile,  to  find  the  initial  velocity  of  rotation  of  a “ 

upon  what  its  velocity  of  rotation  depends “ 

effect  of  its  initial  velocity  on  the  velocity  of  rota- 
tion ...  “ 

effect  of  its  form  on  the  velocity  of  rotation.  .....  “ 
effect  of  its  density  upon  its  velocity  of  rotation  . . 
effect  of  the  distribution  of  its  material,  upon  its 

velocity  of  rotation “ 

effect  of  the  position  of  its  centre  of  gravity,  upon 

its  velocity  of  rotation “ 

objections  to  high  velocity  of  rotation . . . ‘ “ 

velocity  of  rota  cion  required  in  a ‘‘ 

S.xltpetre,  refining  of “ 

description  of  the  process “ 

filtering  of,  in  refining “ 

crystallization  of.  in  refining “ 

washing,  testing,  etc.,  in  refining “ 

testing  for  impurities “ 


7G0 

7u4 


I 0 I 

710 

7i;i 

-710 

725 

728 

72!) 

722 

724 

725 
72G 

727 

728 

747 

748 
740 

750 

751 

752 
752 

754 

755 
750 

757 

758 

759 

701 

702 
702 
705 
700 
708 

708 

709 

729 

740 

741 

742 


744 

745 
740 
740 

1051 

1052 
1052 
1057 
1000 
1001 


33 


INDEX. 


Saltpetre,  drying-  for  storage  or  transport 

extraction  of,  from  damaged  powder 

how  prepared  as  an  ingredient  of  gunpowder 

Sulphur,  where  obtained 

value  as  an  ingredient  of  gunpowder 

soluble  and  insoluble  form  of 

flower  of 

apparatus  for  refining 

process  of  refining 

testing 

how  prepared  as  an  ingredient  of  gunpowder. 

Shell 

Crane’s 

Pevey’s 

mortar 

loaded,  examination  of 

armor  piercing 

care  in  the  use  of 

Smelting  of  iron 

fluxes  used  in 

difficulties  of  obtaining  pure  metal 

of  iron,  composition  of  fluxes 

slag 

cinder 

fuel  used 

Strength  of  a gun,  how  to  increase  the 

Sinking  head 

Sample  gun 

Samples  irom  gun  castings 

Standard  specimens  of  gun  iron 

Shingling ■ 

machines 

Scoring 

Spongers  and  loaders 

Seat  of  the  charge 

Slow'  match 

Sighting  cannon 

Sight,  dispart i . . . . 

tangent 

brass  tangent 

wooden  tangent 

Sights,  pivot  gun . 

for  rifled  guns 

advantage  of  long  radius  between 

adjustment  of 

. breech,  adjustment  of 

reinforce,  adjustment  of  

side,  adjustment  of . . 

marking  tangent 

using 

graduation  for  degrees 

trunnion 

spirit-level  quadrant 

gunner’s  quadrant 

Signals 

Signal  rockets 

the  case 

composition 


Art. 


lOGI 

10()4 

1006 

1067 

1081 

1069 

1069 

1070 
1074 
1080 
1098 

7!b! 
796 
79;l 
794 
819 
858 
1572 
9,  8:17 
10 
11 
12 
1-3 
l:3 
14 
019 
:171 
375 
379 
382 

83 

84 
607 

1577 

211 

1454 

1587 

1583 

1590 

1591 
1591 
1.592 

1593 

1594 

1595 
1599 
1608 
1614 
1622 

1624 

1625 
1 (>55 
Ph54 
1 ()53 

1518 

1519 
15-20 
1521 


INDEX. 


Signal  rockets,  driving 

head 

decorations 

stick  

motive  power 7 

pacldug. ...  

firing 

Signals,  Goshen’s  lights 

compositions  for 

storage  of 

Shrapnel 

to  prepare 

rille 

Steel,  its  peculiarities 

its  distinguishing  properties 

various  kinds 

liigh  and  low 

how  obtained 

puddled "! 

cemented 1 

converting  furnace  fur 

cementation  process 

effect  on  physical  properties  of  the  iron  ....... 

blister 

spring 

tilted 

shear 

cast 

process  of  manufacture 

ingots ....  

hammering,  or  drawing  down  the  ingots 

Bessemer  process  

to  produce  Bessemer  steel  

Bessemer  converter  for 

charging'  the  Bessemer  converter 

chemical  action  in  Bessemer  process 

admission  of  blast  to  Bessemer  converter 

casting  the  ingots,  in  Be.ssomer  process 1 

hammering  the  ingots  in  Be.ssemer  process 

AVhitworth  metal  

annealing  

tempering 

tempering  in  oil 

qualities  of '. 

high,  its  distinguishing  properties 

low,  distinguishing  properties 

advantages 

strength  of 

low,  comparative  value  of  as  a cannon  metal 

Strain,  lands  of,  to'which  a gun  is  subjected  in  firing 

the  two  principal  strains,  to  which  a gun  is  snbj_ected 

tangential 

to  find  the  whole  resistance  of  the  gun  cylinder. . 

to  the 

to  find  the  whole  force  exerted  by  an  explosion  in  a cylinder 

rend  it  longitudinally 

longitudinal,  tendency  of 

longitudinal  rupturing  effort,  to  find  the 


Art.  1523 
“ 1533 

“ 1534 

“ 1535 

153!) 
“ 1537 

1538 
“ 1529 

“ 1533 

“ 1534 

“ 798 

“ 797 

798 

“ 101 

“ 103 

“ 103,  108 
“ 104 

“ 105 

“ 107 

“ 108 

“ 109 

“ no.  111 

“ 113 

“ 113 

“ 114 

“ 114 

“ 115 

“ 118 

“ 117 

“ 118 

“ 119 

“ 120,  138 


123 

123 
125 

124 

138 
137 

139 

130 

131 
133 
173 

173 

174 

175 
178 

183,  185 
376 
230 
377.378 


373,334 


285 

388 

287 


24 


INDEX. 


Strain,  longitudinal  rnpturmg  effort,  to  find  the  resistance  of  the 


gun  to  the Art.  288, 289 

crushing  force “ ' 290 

to  find  an  expression  for  the  effect  of  a ‘‘  291.292 

transverse “ 300 

tendencies  to  rupture “ 308 

bursting  tendency “ 309 

nature  of  the  force  to  be  restrained  in  cannon 018 

method  of  equalizing  the,  in  cannon 023 

Testing  machines ‘‘  390 

Testing  machine,  Rodman’s “ 397 

power  exerted “ 398 

explanation  of ‘‘  399 

main  lever  of ‘‘  400 

small  lever  of “ 401 

combination  of  levers 402 

capacity  of “ 403 

cog  wheel,  gearmg  of “ 404 

multiplication  of  power ‘‘  405 

torsion  lever " 400 

pedestals  for  transverse  strain ‘‘  407 

adjustments  of “ 408 

s.ample  holders “ 409 

obtaining  tensile  strain  of  specimen 

with “ 410 

table  containing  areas  and  logs,  of  va- 
riations of  diameter  in  tensile  sam- 
ples.  “ 411 

determining  transverse  strain  with. . . . 412.413,414 
torsional  strain  with.  .410,417.418.419 
test  of  compression  with 420,421,422 


to  determine  the  indenting  force 


with 423,424.425 

errors  of ‘‘  420 

modifications  of “ 427 

indicator  for. ...  “ 428,429 


Riehlc’s 

the  levers  of 

recording  the  strain 

ajiplication  of  power 

adjustment 

the  differential  lever 

Testing  specimens — elongation,  examples  of 

effect  of  

repeated  breaking  of  same  specimen 

proposed  shape  of  specimens 

advantage  of  long  specimens 

value  of  tests 

Tests  of  iron  while  in  fusion 


h39 

440 

441 

442 

443 

444 
4:2 
433 
435 
430 
437 
381 
353 


Tables  of  fire 

Tangent  firing 

Trunnions,  size  of  ...  . 

position  of 

Vavasseur  gun 

Vent,  definition  of . . . . 

piece  

position  of  ...  . 
enlargement  of. 


1023 

15S9 

197 

198.2.34 

017 

215 

210 

217 

002,004 


INDEX. 


25 


Vent,  impression  of 

closing-  the 

clefiring-  the 

■Wrought  iron, 

peculiarities  of 

how  produced 

conversion  of  crude  into  malleable  iron 

chemical  reactions  dui’ing  the  conversion 

kind  of  iron  most  suitable  for  conversion 

refining  process 

rolling  mills 

reheating  in  rolling  mills 

forge  cinder 

mill  cinder • 

piling  puddled  bars 

rolling  bars,  details  of  manipulation 

crop-ends 

rolled  armor  plates 

effect  of  rolling. . . : 

effect  of  powerful  vibrations 

judging  its  quality  by  character  of  fracture.  . . 

variations  in  quality • • . ■ 

■welding 

poiter-bars 

upsetting 

scarfing 

welding  large  pieces 

qualities  of 

strength  of 

uniformity  of 

comparative  value  of.  as  a cannon  metal 

Wrought  iron  guns,  detection  of  weakness  -in 

inability  to  resist  compression  and  wear- 

want  of  homogeniety 

Woolwich  gun 

details  of 

the  A tube 

the  B tube 

the  breech  coil 

the  casoabel 

building  up 

nomenclature  of 

Whitworth  gun 

Windage 

Water-proof 


Arts.  506,, 
Art. 


U 


Arts. 

Art, 


597,610 

1575 

1576 
66 

67.91 

68,70 

69 

71 

72 

73 
86 
87 

87,100 

87 

88 
89 

89 

90 

92 

93 

94 

95 

96 

97 

98 

99 
100 
168 
168 

169 
182.185 

170 

171 

172 
661 
662 

663 

664 

665 

666 
667 
670 
675 

208,210 

599 


9 


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